Structural Concerns with Adobe

Quentin Wilson and Associates, specializes in solar adobe design and construction. He grew up in the South Valley of Albuquerque, New Mexico where he watched adobe bricks being made. In the fifth grade, he made miniature adobes on cookie sheets in his mother’s oven in order to construct house models for a class assignment. By age thirteen he made full-sized adobes in the back yard and ruined the grass. Later, he traveled a bit, went through the Army, and graduated eventually from the University of New Mexico with a major in physics, minors in math, chemistry, and education in 1970. After teaching high school two years and community college math for three more, Quentin moved into professional solar adobe construction in 1976 as the Project Manager and Instructor for the Sundwellings Demonstration Project at Ghost Ranch, Abiquiu, NM. He became a licensed general contractor in the State of New Mexico in 1982. He has been building homes and teaching seminars and workshops ever since. In the fall of 1995 he established and taught the full-time Adobe Construction Program at Northern New Mexico Community College. His website, quentinwilson.com, lists the course schedule and many other resources related to working with adobe.

Q: I am working on an old adobe (130+ years) and need to know the maximum height for a 12in. thick wall. Would a poured in place concrete beam help to strengthen the wall.

A: Maximum wall height is ten times the wall thickness. That is called the aspect ratio and has been known since biblical times. It is in some codes although many times a code just states that certain brick sizes are suitable for one- or two-story construction. A poured in place concrete bond beam would indeed tie the building together and spread roof loads on the wall. In NM wood bond beams are also allowed and might be easier to do. Three layers of 2" lumber or four layers of 1-1/2" lumber give the required six-inch high by 10-inch wide bond beam. Boards are staggered especially at corners to give interlocking lap joints.

Q: I am an architecture student. I will design a project outside of Phoenix, Arizona, made out of earth. I want to know what is the maximal height for a tower out of earth, and which will be the best structural material if is not possible to realize one tower (possibly with a rectangular base), only with earth for a height of 20 floor for example.

A: The highest existing adobe buildings are in South Yemen. They are seven- to eleven- stories high. The Tower of Babel may have been higher. Adobe has an aspect ratio of 1/10. That is the wall height can be ten times the thickness of the base. To go one-hundred feet high, the wall at the base should be ten-feet thick and should be battered (tapered) to ten or twenty-inches thick at the top. If you built a round tower the total diameter of the tower might be considered as a basis for the aspect ratio and the walls could be thinner allowing for an internal stair or habitation area, but I would not know how to calculate that. Right now the New Mexico building code limits construction to two stories.

Q: I have a friends home in carmel CA which was partially built with adobe bricks. We are having a deterioration problem with the walls. One wall acts also as a retaining wall so is subject to constant moisture, the other walls are typical exterior walls. I would appreciate it if you could direct me to some source of maintenance information to deal with this type of problem.

A: Ageless Adobe: History and Preservation in Southwestern Architecture by Jerome Iowa, 1985 This history of architecture in the American Southwest presents conservation and preservation of adobe buildings and suggestions for solar options. Photographs and drawings make this a document of unusual value for all interested in preservation, rehabilitation or construction.

Q: I'm looking at building a hybrid adobe/Earth sheltered cabin that would be built half into a hill. If I were to choose this approach, what measures need to be taken to protect the adobe that is bermed, if any?

A: Shouldn't build adobe below the finished grade.

Q: What sort of insulation and structural design would you suggest for the ceiling/roof of the structure?

A: Heavy timbers/joists lots of straw, twelve inches of dirt.

Q: We are building a home on Bowen Island Canada. We have had to build over an area which is partly fill. It is pretty solid material, and we can remove all organic material, put some rubble in and so forth to stabilize it and prepare for the adobe flooring, but the process is costly. It looks like it may be cheaper to build a standard hanging wood floor with a crawl space, instead of building directly onto the sub-floor as we had planned. We would still like to use the adobe flooring, with radiant pipes in it. What is the experience base of building adobe onto a wood subfloor..along with the standard gravel, vapor barrier, insulation etc. Does the very slight give in the wood make adobe untenable?

A: Adobe does just fine over wood subfloors. It will take longer to dry due to the required vapor barrier below it and moisture can only move upward. There is no need for gravel. The techniques for the floor would be the same as pouring a concrete floor over a suspended wood floor: it has to be very strong to handle the dead load of the adobe which at three inches thickness will be about 30 to 35 pounds per square foot added to whatever the dead load of the wood system would be.

Q: I purchased a ranch with an adobe roof on one of the buildings. The roof leaks. Without walking on the roof (makes more leaks) is there something I can spray on the roof to retain most, if not all, of the look and seal the leaks?

A: Oddly enough, more dirt might help. Sometimes it blows off or washes off in a rain. If walking on it makes things worse, then it could be that the boards underneath have gotten rotten and dirt falls through. In that case, add more dirt carefully. Sometimes we have just had to remove the dirt, replace the boards and then put the dirt back or in worse cases, use modern foam insulation covered by a hot mop roof. Lots of old dirt roofs in the Santa Fe area got a hot mop roof on top. I can't think of any easy fix that can be sprayed on. Asphalt driveways can be sealed with cold process asphalt, also known as emulsified asphalt. It is used also to stabilize adobe bricks. Home Building Suppliers usually have it. I have no experience with it but it might be worth the experiment. Farm ponds are sometimes sealed with a Bentonite clay but I think it has to be continuously wet for the Bentonite to work.

Q: We recently moved to the grasslands of Sonoita, Arizona. We are considering an adobe patio wall, parts of it will be a retaining wall. Is this a problem with adobe, especially if it has some concrete in the block and if I seal it on the earth side of the wall?

A: The New Mexico Adobe Code does not allow using adobe below grade. Adobes need to be on a concrete foundation that extends 6- to 8- inches above the finished grade level. Adobes have been used as retaining walls historically and sometimes they last a surprisingly long time. Nevertheless, neither the Code nor I recommend it. Adobe walls have little resistance to lateral forces so if the run of the wall is long and the height of the soil is significant (12-inches or more) the wall would be expected to move before long. There is not much on the market that can truly seal off a wall from moisture.

Q: The person who is helping design the yard suggested the adobe and thought we would have to add rebar for the strength needed. I wondered if drilling the adobe would ultimately weaken it, even if we used some concrete in the adobe mixture. Would that possibly work? Also, we have about 19 inches annual rainfall, so that might present another problem with the longevity of the wall. If adobe is not a realistic option, what would you suggest for a natural looking wall that will blend with the environment?

A: (Kelly) You are right that drilling holes through the adobe blocks would either weaken, or more likely actually crack the adobe. I agree with Quentin that this is not a good material for this purpose. My suggestion would be to build the wall with natural stone, either dry stacked or mortared. Dry stacking has the advantage that it will allow the wall to weep water if necessary, so pressure will not build up behind it. It takes some experience to do a good job of stacking stones for a retaining wall, so either read up on it, or find someone with experience to help.

Q: I have exposed viga posts and I have found that these posts are rotting as well. These are vertical. Apparently, the footing was poured too low and now the bottoms of he posts are decayed. The worst one (as far as I can tell - since I can't see into the interior of the posts) has lost about 1 foot of length at the bottom. This has to be replaced, I know. I think I should replace them all after pouring the concrete footer up a little higher - above the brick porch floor so no water ever contacts the posts. I understand there is a metal viga base that can be used to cover the concrete which would otherwise show.

A: It would be relatively easy to support the porch on each side of each post with 2x4's or 4x4's while the rotted part of the viga posts are cut off. A sharp carpenter could make a form for a concrete pillar that would come up to the bottom of the intact viga. With a little care the pillar can be designed with a slope on it's top surface all the way around so that any rainwater that hits it will drain off and not puddle up under the viga. The concrete pillar could have beveled edges to make it look neater or it could have flagstone stacked around it to conceal the concrete. In fact the pillar can be built with stacked, mortared flagstone. A rebar from top to bottom of the pillar would be in order.

Q: Do you know of anyone who would be willing/able to do this and do it correctly, in this area?

A: I have had the experience of dealing with recently arrived Mexicans who do not present themselves very well but turn out to be spectacular workers and problems solvers. Or you can do pickup truck profiling:
2004 Dodge Diesel Dually: Too expensive, you have to help him make his payment this month.
1976 Ford with the tailpipe dragging and two fenders bent: A bit careless and fly-by-night.
1998 Toyota T-100 with a lumber rack and no more than 30% of the dashboard covered with paperwork: Perfect.

Q and A: My husband and I are making an offer to by a 1939 tudor cottage style home in Phoenix Arizona. The home is made of adobe and has an adobe roof, (Probably clay tile. Adobe roofs are flat and very rare in USA) or so says the agent and the listing information. We like the house and we LOVE the idea of living in an adobe house but how does someone who isn't an expert find out the condition of the adobe both in the structure and the roof? (There is a lot of adobe construction old and new around Tucson. There should be some knowledgeable home inspectors in the area. Sorry to say, I am out of touch with the Tucson scene.) The structure is painted and looks solid but the roof has tiles that look like shingles and are curved upward. They are a whitish color that has black residue perhaps from tree residue or who know what that is??? (Leaf detritus is often the culprit on roofs.) I did a search for adobe roofs...hmmm. There were very few pitched roof adobe houses except in the tudor revival style but no mention of adobe in the roof. What is you experience with this? (As above) What questions would you ask the seller or even better the inspector to make sure that we are purchasing a sound home with a roof that will last. (I am sure that the roofing material is something that most Tucson area roofers would be familiar with and would be able to evaluate. If you have a good roof and a good foundation, the wall material in between will last forever whether it is adobe, frame, metal or masonry. So check the foundation also.)

Q: I own a thirty year old adobe house with a flat roof and would like to consider putting on a pitched metal roof. The house is a single story on a concrete slab. The walls are adobe and are one brick thick. I know that this is difficult to answer without seeing the home but but do you have any thoughts or advice?Is the weight a problem? Do the parapets need to be removed?

A: Should you be in the state of New Mexico, the adobe part of the building code has been recently interpreted to mean that fourteen inch walls are required below if the pitched roof system includes any second floor living space. I got one retrofit accepted on the condition that the pitched roof start right above the vigas on ten-inch adobe walls below. Interpretation and enforcement of the code rules are not consistent. You may be in an area where a permit is not needed. The short answer, then is that you can feel pretty secure in adding a pitched roof to your home. It is a routine addition to homes here in the high country of NM. I would indeed remove the parapet and begin the pitched roof on a wood plate shimmed to level and well nailed or screwed or lagged to the vigas. If you do want attic space we should continue the conversation.

Q: We are replacing the covered porch supports of our Boulder, CO home. We are installing upright vigas and corbels with a cross beam that supports the existing 2x4 rafters. The vigas will sit on the concrete pad of the porch. (We have been planning to hammer drill holes in the concrete for large pegs to go up inside the viga and down into the concrete.) We are trying to figure out attachments - How to attach the corbel to the viga, how to attach the corbel to the cross beam and how to attach the bottom of the viga to the concrete pad. We have looked at pictures and can't see any hardware or obvious means of attachment. How is it done?

A: Use a long lag screw that gets six- to eight-inches into the viga. You may want to counterbore the corbel so that the hex head and washer under the lag screw are not above the corbel. Screw up from the corbel into the cross beam using 6-inch deck screws or timber screws or lag screws. Pick the place where it will show the least and again, counterboring may be useful. You can counterbore enough to fill the hole with wood filler or even a wood plug. If you can work from above it will give a neater look to lag from the beam into the corbel. Try to find something to go under the viga post to keep it above the concrete and standing water: flagstone; a metal base such as those made by Simpson Company which specializes in metal connectors and is found at most any builders' supply; or a round poured cement shoulder. Drill into the concrete and epoxy in a piece of rebar that will go eight-inches or more into the viga post. For a 1/2-inch rebar, pre-drill the viga at that diameter. The knurling on the rebar makes it larger and the viga will have to be pounded down onto the rebar. A Simpson 6 x6 post base can be modified to do the entire job but you might have to think up some trim at the base of the viga to hide it. If you are pouring new concrete an anchor bolt and Simpson post base would be easiest. A clever welder could make you a similar unit that was round - for a price. If you cannot drop the elements down from the top and have to shoehorn them into position, it can all be toe-screwed together with those 6" deck screws. Predrilling with a slightly undersized extra long drill bit will allow you to get the screws in just where you want them before the Phillips head screw strips. Counterboring can make it all look neat. Timber screws are also great, but they have a larger head that is harder to hide. They are hex heads and never break or strip. I use TimberLok brand from OMG FastenMaster. 800-633-3800. It is a pleasure to answer an actual construction question.

Q: I just finished an Adobe floor in Tucson AZ. It is beautiful, but I could use some advice. We laid down an octagonal form made of 2x2's. we leveled the floor and pounded in the adobe. The problem is that the adobe , although packed against the form but not above, had seemed to pull away from the form and the form is "popping up" in a few places. Do you have any suggestions on how to solve the problem. I have thought of re packing the adobe and pre drilling the form and possibly finding some long screws to act as an anchor. Please help.

A: The form remains in place? If so there are 6-inch deck screws that might help hold it down depending on what is below it. Several companies also make timber frame connectors up to at least 10-inches if not longer. Where the adobe has pulled away from the form you can pour in a thin slip of adobe mud to fill the space. We just did an adobe floor today and poured it about 5-inches thick. The weather is still cool and we have no idea how long it will take to dry out.

Q: Restoring 100+ yr. old adobe in San Jorge, Nicaragua - the oldest house in the pueblo. The walls were repeatedly patched with concrete, and one side was plastered with concrete. This is a humble farmers house, so the walls are rustic and uneven. Can we replaster with adobe over the concrete patches or must they all be removed (ARRGH!) and replaced with mud. Suggestions to improve plaster adherence?

A: Adobe plaster usually sticks very well to cement/lime based plaster or concrete. If not a little wheat paste glue as used by wall paper hanger or made by someone's grandmother on the back of the stove will help. Elmer's white glue or its equivalent can also be used. Sometimes, there is great satisfaction in pulling off concrete and replacing it with adobe mud.

Q: We are purchasing a home in Penasco, New Mexico. It is an adobe home with a pitched roof, very old but in good condition. My husband and I are fixing it up to what we want, so some walls need to come down (old adobe houses are like mazes). But we aren't sure how to take an adobe wall down with out damaging some of the adobe for future use, any suggestions?

A: Have to make sure the walls are not holding anything up, like ceilings. It is not terribly difficult to enlarge doorways or windows with bigger lintels or even arches. Some folks remove bearing walls by placing a large beam under the vigas or joists and supporting the beam with posts or masonry columns at the ends and sometimes in the middle. Wear a hard hat.

Q: I'm a construction consultant in Santa Barbara, Calif. and I have the challenge of mitigating water entrainment that appears to be migrating through the walls of a beautiful adobe building here. I found your site through a search engine that pointed me to the article by Quentin Wilson that you have posted. In that article Quentin mentioned a product called Okon W-1 and W2. I thought it might be prudent to talk to him or to yourself and ask if there are any other products that you might recommend for application to the exterior of adobe walls to restrict or inhibit the migration of rainwater.

A: This situation can get complicated. If the moisture is seen in the lower portions of the wall, it may be rising from the foundation. Many buildings have had various types of impermeable materials applied to walls only to find that they hold in water that would otherwise be evaporating from the wall surfaces. If it can be determined with certainty that the water source is rain then there are several exterior treatments that can be made. I am not sure if Okon W-1 and -2 are appropriate for exterior surfaces but certainly one of their products should work. One advantage of the W's is that they are essentially invisible. Their webpage is at: http://www.okoninc.com/home.htm The best product is one that is waterproof to stop incoming rain but vapor permeable so that any moisture that gets into the wall has the opportunity to get back out as water vapor. My recollection is that a permeability of 5 or 6 perms is desirable. It is not easy to predict the permeability of a field applied material. Usually perm ratings are determined in a laboratory using manufactured building materials. El Rey Stucco in El Paso has a product called Adobe Sealer which they claim has appropriate permeability. It may now called Crown Seal. The specifications seem the same. http://elrey.com/

Q: I am purchasing an old adobe place in San Fidel, N.M. that has 3600 sq. ft. of floor with 2000 sq.ft. of it with no roof. All Adobe walls and well worth renovating. One 800 sq. ft. room has for rafters, logs, that have been incorporated into the adobe walls themselves, and the logs have rotted out and need to be replaced. And since money is a problem I was wondering would it be cheaper if I were to remove the logs entirely and go to a more conventional type of rafter or dig the logs out of the wall and just replace them with newer logs? And any suggestions on a sealant for where the logs make contact with the adobe?

A: Conventional rafters might well be cheaper as long as they are big enough to hold up the roof load. Usually the logs (vigas) are more likely to be intact in the wall while they rot in the open air of the ceiling system. Lots of the old pueblo and spanish buildings still have the intact stubs of the vigas in the walls while the rest of the roof system has disappeared. If the original vigas protruded outside the exterior surface of the wall, then that can be a source of moisture and rot. As for treating the new beams or vigas, there is little stuff available that will kill varmints, rot, or bugs that I would want to have inside the house with me. I would consider soaking wood in a solution of Borax, 20 Mule Team. It is effective but if it gets wet the Borax is washed out. Therefore, protecting the wood from moisture is very important.

Q: I am presently doing a landscape project for a friend.It is in a Hawaiian theme. One aspect of our landscape is a fishpond with a waterfall dropping from a volcano behind it. The volcano would be constructed mainly from the dirt dug out of the pond. Within the volcano is a Mexican fireplace called a "chiminia",with its mouth opening facing out the backside of the volcano. The volcano will sit on a reinforced cement slab. I have already constructed a small cement block wall at the base of the volcano, but behind the waterfall,which will help support the dirt and make the elevation for the waterfall. Behind the wall sits the fireplace.What I'm intending to do, basically, is make an adobe filler/base to enclose and support the fireplace and lava rock covering the volcano. Within the volcano and around the fireplace will be 2X4 or 6X6 mesh that's connected to the rebar within the slab that everything sits on. I'm going to shape the mesh to give me a form of the volcano. Now, my concern is this: We get on average of about 20" of rain a year here in the Bay area. Is the adobe a good structural mass for supporting the volcano??? Will we get a "muddy water runoff" when it rains??? And, if I were to use asphalt within the adobe to water proof the mound, could it contaminate the pond water???

A: Wowee! If ever there were a difficult task for adobe this is about it! Of course there was the time that the Mexican idol Juan Gabriel proposed to recreate a Mayan village in Tesuque, NM not far from the Santa Fe Ski area. He wanted to solar heat the open air palapas in addition to everything else.

Anyway, adobe that gets wet will slump and suffer compression failure. If it remains dry, it can certainly provide the structural strength to support most anything. It can be stabilized with emulsified asphalt with about 12 ounces of asphalt per cubic foot. There will be little asphalt that will leach into the water after the first couple of days. My best recommendation would be to do the whole project out of cement based materials and avoid having to experiment at the leading edge of adobe experience.

Q: Do you have any advice for the best methods for hanging pictures on adobe walls?

A: Sheet rock screws with coarse threads or gold deck screws get a good bite in adobe walls if they are about three-inches long or four. Drive them in at a slight downward angle. I use a battery powered drill/driver and it takes a powerful one to get the screws in.

Q: I am at a loss to find any resource that will tell you how to wire an adobe wall (before construction).

A: Depends a bit on where you are. The National Electrical Code says to use type NMC cable in an adobe wall. That is called barn cable in places where it is available. It is just like Romex but has no paper wrap within the sheeting. The New Mexico Addenda to the NEC upgrades the requirement to UF cable which is Underground Feeder. UF costs more than Romex and is harder to strip and work with.

The standard method of an electrician is to wire a house once the roof is on. That is too late for an adobe structure. It can be done and is done on retrofit jobs but it is so much easier to to the work as the walls go up. Same thing for plumbing, as a matter of fact. No cutting, drilling, thumping, whacking, bending forcing, etc.

Just lay the cable in the middle of the wall at about the third course around 12-inches off the finish floor level. The cable gets buried in the mortar. I strongly recommend the use of steel boxes because each one of them contributes surface in contact with the adobe which adds to the grounding system. We use four square boxes with plaster rings on the front. Just set the box on the wall and run cable in and out. The next course surrounds the box with a little chipping on adobe bricks to fit around it. The boxes can be held in place by 16d nails or 3-1/2 inch deck screws or clever use of tie wire. The electrical cable itself which is clamped into the metal boxes insures that the boxes are not going anywhere. With the cable in the middle of the mortar joint, there is little chance that it
will ever be hit by a nail or screw. We add the plaster rings later on just before the plaster and we can choose from several depths to suit how each box sits in the wall in relation to how much plaster we think we will use. This takes care of the general convenience outlet circuits.

Going around door openings requires some ingenuity. You can go up and over rough bucks or under with a conduit. Some folks in fact use conduit throughout but I don't think it is worth the trouble or expense.

Switches and lights are mounted higher up and may require some vertical runs which can be stair-stepped up the coursework in the mortar joint or can be in channels which are chiseled in the wall. The Code requires that cable be buried 2-inches into the wall.

In New Mexico you can get a permit to do your own wiring as an owner-builder. The permit must be acquired before you start work and requires submission of an electrical plan showing all circuits, switches, outlets, lights, and special circuits for anything with a motor. You may be subjected by an inspector to a simple or brutal test.

There are rules as to how many devices can be on one general circuit; rules as to how many wires can be in one foursquare box; rules as to how many circuits and what their size may be connecting into a service entrance. This takes some study on your part or partnering with a friendly electrician who will lead you through the process of designing the system. She might even be willing to be the electrician of record an get the permit and do whatever overwhelms you.

My system is to use an adobe friendly electrician who supplies me with the cable and boxes to install in the coursework. He then installs the meter, main box, and does all the actual wiring in the boxes including installation of devices and cover plates. We just stuff the UF into the metal boxes in a manner of which he approves. Using this system, we can do the electrical rough-in faster than in a frame house. Plumbing, too.

Our walls go up a bit slower (by about a day or two) but when we are done with the walls, we are done with the heavy work of the rough-ins. Any channels cut in walls for cable or runs over/under doors should be photographed for future reference since the cable could be hit by nails later on.

Fine Homebuilding's Taunton Press has books on wiring and plumbing. Libraries and building supply stores have several selections.

Q: Instead of insulating the outside of adobe and then having to mess with wire, can I lay a double wall (bricks of 4x51/2x16)leave an inch of space (giving me a 12" wall) and fill it with insulation. If I did that, could I lay electrical wire on the insulation?

A: That would be a great solution. I would try to expand the space to two or more inches and use a type of insulation that gave at least R-11 or better yet, R-19. If you use loose insulation it should be as light weight as possible. Loose insulation actually imposes a lateral force on the walls just like hydrostatic pressure, although much reduced. In any case, you will need to tie the two walls together at every third or fourth course. DuroWall which is the 10-guage ladder type wire reinforcing used in concrete block walls will work. It comes in several widths which are about 2-inches less than the stated, nominal size.

I think you should certainly be able to lay the electrical wire on the insulation. It is in contact with the insulation in a frame wall system. It will be useful to discuss your proposed wall system with the building inspector beforehand if you are planning to get a permit.

Q: I'm an architecture student from the Philippines and I'm using adobe for my thesis which is low-cost housing. I'm wondering about its structural component, what kind of beams and posts are to be used in this kind of construction? Reinforced concrete beams are not that eco-friendly, are there other cheap alternatives? Is it also possible to build with adobe below ground level? Can it accommodate a roof garden?

A: In New Mexico we just build things with adobe. No posts nor beams are needed. The material has a compressive strength of about 300 psi, a modulus of rupture of about 50 psi and a tensile strength that is low enough that we don't usually try to measure it. Minimum wall thickness is 10-inches for single story construction. Two-story construction may be done with 14-inch walls below and 10-inch walls on the second story. Or the walls can be built 20-inches wide from top to bottom. In general we observe an aspect ratio of 10, where the walls height may be ten times the wall thickness.

The compressive strength and modulus of rupture may seem a bit low to structural analysts. As it turns out, since the walls are monolithic, adobe structures are among the most powerfully built today. You are in luck and may indeed place a roof garden on adobe walls. The earliest adobe homes in New Mexico had 6- to 12- inches of dirt on top of the vigas and latillas which formed the structural and deck parts of the roof respectively. You will just have to be careful to find appropriately sized beams or vigas which can span across the walls and carry the loads of the roof garden. A waterproof membrane would also be useful in modern times. The old ones had none.

Because of its strength, it would be a shame to waste the ability of adobe to form structural, supporting walls. In post-and-beam construction the adobe would be just infill in a system that did not even come close to the powerful carrying capacity of the adobe itself. Concrete post and beam is practiced in parts of California as a way to meet anti-seismic code regulations. There are many other ways to make adobe walls anti-seismic.

It is against the New Mexico Code to use adobes below grade. They should be on a foundation that gets them 8-inches above the finished grade. Code aside, there are historic adobe structures including my own home where the adobe bricks begin at or below grade. I might not attempt that in a damp climate.

Adobes are expected to be found in arid climates. However, there are some two million earthen homes in central Germany. They are found in many other equally surprising places. In the damp climates extra care should be taken with the foundation and roof systems. But that is not true of adobe alone: wood rots, metal rusts, porous materials develop mildew, rot, fungus and mold.

Q: I am going to stack adobe bricks against a Structolite wall behind my wood stove. Can I use masonry cement for the mortar between adobe bricks and to adhere to the Structolite wall? I then want to seal the bricks for protection but showing brick look.

A: You can certainly use masonry cement (one part mixed with three parts plaster sand) as the mortar between the adobe bricks. You can also use just plain dirt that does not have much organic matter in it. If it has about 30% clay and 70% sand, it makes perfect mortar and is very similar to the material in the adobe bricks themselves. If the dirt mortar is too sticky and won't come off shovels and trowels, then add sand to the mix until it is less sticky.

The cement will not bond well with the structolite and in fact the two materials are somewhat incompatible. Hardware stores sell brick ties which are little wavy bands of metal with holes punched for nails. Simpson Strong-Tie BT-R-100 works. www.strongtie.com Nail the ties through the first hole through the structolite into the framing behind or if the wall behind is adobe use 4-inch gold deck screws. Then bend the remainder of the brick tie so that it lies in the mortar joint between adobe courses. No nails are needed. Ties should be approximately every 16-inches horizontally and vertically. The adobe bricks can be sealed with OKON W-1 which will not change their color at all. www.okoninc.com

Q: I need to build a sound wall 400 ft long and 10 feet high. I was thinking of 10 x 14 x 4 adobe laid sideways so the wall would be 14 thick. How high and how far apart do I need to build the "side supports" that stair step down to ground level? also the asphalt emulsion I found is called ssi. is one pint per cubic foot (3 adobes sufficient)? the sand in the soil here is blow sand. The particles under a microscope are rounded instead of faceted, am I over analyzing?

A: The side supports can be buttresses or pilasters. Buttresses can go to any height at or above 2/3 of the total wall height. They can step down or be sloped so at the base they are 1/3 of the total wall height. Buttresses should be spaced no further than 24-feet apart. This is for buttresses on one side of the wall only. If buttress were on both sides I have no information but presume they could be narrower.

Pilasters are a thickening of the wall without taper from the bottom to the top. Pilaster blocks are sold in the concrete block trade for just such purposes and are "H" shaped and are sized so that the blocks of the wall fit into them. They can be seen as ribs on the walls of many large block buildings. For 14" adobe walls, the pilasters could be two adobes laid the other way to give a 14" long by 20" wide column at intervals in the 14" wall. Pilasters could also be spaced at 24' intervals but 16' intervals might be better.

Q: We are thinking of building an adobe structure in a few yrs on a 1/4 acre in Tres Piedras N.M._ being of course -completely off grid- solar passive/cistern/ compost toilet - We would love to build it ourselves however we don't really know anything about building- I want it to last- but funding in an issue-- I would like the adobe structure to have a Dome Loft top but not to cover the entire roof- I'd like the front part to come out lying flat and run along the south side /slant windows & planting beds open hallway enclosed underneath- not sure if I'm painting a picture here -- How can I make the dome structure on top but not encompass the whole roof top? Would it be hard to build myself or very expensive for a building company? What would one use to build the dome this way? I would also like to build the dome to have windows in it, but to not look so much like a steeple but to show the exposed wood wall beams.

A: Adobe homes last as well as any other if they have a good foundation and a competent roof. You can certainly do part of the roof with a dome but the dome which can be round needs four sturdy walls forming a square under it for support. The dome can be oblong on four rectangle forming walls. It then is called a boveda or can be built as a vault. You can build an adobe dome yourself without much trouble. I don't know of any professional builders in the area doing domes at present. The dome can have windows if they are placed and sized correctly.

As for your slanted glass below, I will work hard to try to convince you to make the glass vertical. It will actually collect more heat in the winter due to reflection from the ground in front, and in the summer it will be shaded by a short overhang so that the greenhouse does not overheat ferociously. You can see the numbers in the insulation data tables of Edward Mazria's book,  The Passive Solar Home.

Q: My husband and I live in Farmington, NM and are very serious about purchasing a house that is adobe and 80 yrs old.It has a very big attic an it is not flat roof, it goes up on all 4 sides. It is about 1,000 sq ft. It is plastered inside and out now and the walls appear to be 14in thick. Here are the questions- can we take out an interior wall to make an archway? Can exterior windows also be enlarged for replacement windows?

A: It's easy to make an arch in an adobe wall. Just mark it on both sides and start chipping. The adobes in the wall form a natural arch and will not fall out. Maybe the very top one, but that is unlikely. Then just cover the inside of the arch with expanded metal lath which can extend around the walls 4" or more. Then plaster. It's that easy!

It is easy to enlarge windows by making the bottom lower. It is hard to go up because there is expected to be a wood lintel above which extends into the adobe wall to spread the load above. Windows can usually be widened by a couple of inches on each side without compromising the ability of the lintel to spread the load. Going up with a window requires removing the lintel and installing a new one. That's a difficult but not impossible job. If you decide to do that I can give further instruction.

Q: I would like to know the spanning strength of adobe. How large an opening can you create under a large wall (maybe 24 ft. tall)? Can you build a cantilever with adobe? And how would you reinforce these? Do you always need an arch and thick buttresses to support the wall above an opening?

A: Regular, unfired, adobe bricks don't have much spanning strength.They are near zero in tensile strength and have only about 50psi in modulus of rupture. Therefore, we generally do everything we can to avoid their spanning openings. Sometimes when we take out an old window or door frame, we are surprised that three or four adobes above will stay in place and not drop down.

So it is best to span openings with a wood, stone, steel or concrete lintel that extends 12 to 18 inches onto each of the adobe walls at the sides of the opening. Arches also work perfectly fine. In an adobe wall the arches should not be too flat and a catenary or half circle work best. Flatter arches are okay as long as the line of force from the last arch brick stay with in solid wall. I could draw a picture by security is going to toss me out of the building in 38-seconds.

With a properly done arch or lintel there is no problem going as high above that as you wish. A 24-foot wall should be about thirty inches wide at the base in order to stay within the aspect ratio of 10 for adobe. That is the wall height should be no more than ten times the width. As a matter of fact, even if the lintel or arch are not right, with a lot of wall above the opening, there is a natural arch there and nothing above it will fall out no matter how badly done the opening below it. I got this information from the late engineer, Tom Gordon, of Santa Fe and our very own adobe master, the late P. G. McHenry.

Corbeled arches work just fine with adobe. We usually start out catenary arches for doorways by corbelling up about two-thirds of the distance and then begin to roll the adobes over once the curve tightens.

Q: We are trying to decide whether to build with adobe or not. Our main concern is earthquakes and I have been told that there is a flat rebar that looks like a ladder and lays flat along a layer of bricks. Do you know of this or what is recommended for earthquake safety in adobe houses?

A: The ladder-like reinforcing you mention is a common material used in most buildings built with concrete block. Many lumberyards and certainly those that sell block will carry it. Most folks call it DuroWall because that is one of the most common brands available. The sizes are nominal based on the width of the block wall. An 8-inch Durowall is more like 6-inches actual so it rides near the center of the block web in the mortar joint. We have used it on several houses at every fifth course. We use 10-inch nominal for a 10-inch adobe wall. 8-inch nominal works fine and is especially useful because it wraps around 2x6 rough bucks placed in openings for door and window anchoring.

As for earthquake safety, I have no advice. The mission churches are still standing in California. Homes with good foundations and a good wood or concrete bond beam at the top have survived quakes. Openings should not b close to corners and there should be shear panels - just a big solid portion - in each wall. Roof systems need to be very well tied to the wall system. If your are in California, there is abundant help or hindrance to be found in the seismic portions of the various building codes around the state.

Adobes and their performance in earthquake situations is one of the very hot topics around the world at conferences and in the professional literature. Bob Barnes who used to have Old Pueblo Adobe in Tucson would analyze homes on a wall-by-wall basis. He is in retirement but still might do this analysis work. Fred Webster is well known in adobe/earthquake circles as he used to run the shake table in Palo Alto. Still does, I think. Marcel Blondet has done extensive work at the Catholic Pontifical University in Lima Peru. He has a big shake table.

I found Fred Webster's website and it's the most comprehensive and easiest to understand. His message, as I interpret it, is that a few simple techniques will greatly improve the ability of a house to withstand an earthquake.
What he actually says is: V= (2.75/Rw)ZIW He goes on to add that: Fp=Z I Cp Wp Kidding aside, he really is easy to understand and gives great information through his fine drawings and prose. Do your homework at: http://www.deatech.com/natural/cobinfo/adobe.html

Q: I want to do a double adobe wall consisting of 2-10" bricks with a 4" space for a total thickness of 24". In the 4" void I wanted to use expandable foam. This seem to me to be a great idea as sprayed in foam sticks to everything, expanding to fill cracks etc. Also it would tie the two walls together. My concerns is: would the different expansion rates of the out/inside and foam create any problems such as cracking buckling and so on. I plan on putting a bond beam on top and use either re-bar or those masonry reinforcement zigzag things to additionally tie the two walls together. Given the foam sandwich do you think the extra re-bar would be over kill?

A: This would probably work nicely. However expanding foams are usually rated around 7 R-values per inch. That is well beyond the point of diminishing returns and two-inches would be plenty. There are several different rates of expansion and the most expansive might be able to create enough pressure to move the walls apart a bit if the whole cavity were sprayed at one time. Done a little bit at a time as you go up would work. The small cans available in hardware stores would be expensive. You can buy 25 and 50-pound canisters from the wholesalers who supply the insulation
contractors. Or you could have a professional crew do it for about the same price. Polyurethane does stick to most anything including adobes as long as the adobes themselves are sound. Rebar or the Durowall zigzags would be a good idea just in case. Neither costs too much nor takes much time to install.

Q & A: Will archways between rooms have a significant effect on the load bearing strength of the wall?

No, the adobe walls are about the most load bearing capable walls being built today. A few or a lot of arches can be tolerated.

What about windows and doors?  How wide can you go with an archway?

Nearly any width is possible with a semicircular arch. There needs to be a few feet of solid wall above the arch so the limit becomes the height of the wall.

I am thinking that I want to build an archway, or lots of them actually when I build my home.  I was thinking of using regular blocks and a wood form to build the arch.

That's how we do it in new construction.

Rather than cutting the arch out of a wall.

That's how we do it in renovation/remodel work.

It this a better technique?   I may just build an arch on my land just to do it.

Regular bricks rolled up and over the form is much faster since you don't have to build the part of the wall that is later cut out.

Q: I am looking into repairing an 80+ year old adobe building that used to be a bakery and turning it into a restaurant. The flat roof was replaced with a pitched roof about 60 years ago. The biggest problem is sometime in the pitched roof's history it was repaired with tin that does not extend over the top of one section of wall . The wall was exposed to moisture and over the years the adobe has crumbled and fallen into the front room and away from the stucco exterior. The stucco is still there are looks to be in pretty good shape. Can it be repaired and if so is it worth it?

A: Our class just looked at a house with a metal roof that dropped water right on the wall. It is hard to imagine what people might have been thinking at the time. If you don't have to do too much rebuilding of the roof to get the water off to where it should have been, then the building is worth saving. It's fairly easy to replace adobes from the inside with some mortar (mud or cement based) sloshed up against the stucco to effect a decent repair.

Q: I am moving into my family's old adobe home in AZ. It is said to be built in the 1850s. I am in a wheelchair and need to widen the door to get around in and out of the house. Can you tell me the best way to do it myself . How do I put a wider lentil in and new jams .

A: A doorway can be widened a couple of inches on each side if the original lintel is not too short. Meaning, there should be at least 8-inches of lintel on each side bearing on the adobe. If that is not the case, the use of heavy lumber such as rough cut 2x 10's for the jambs that are installed tight against the lintel will allow the weight on the lintel to be transferred to the jambs and the foundation or floor or whatever might be below. On an old house you might have to pour a little concrete to provide a strong base for the jambs.With smaller jambs you can anchor to the adobe walls with 6-inch sheetrock screws or you can use big nail spikes if they don't split the adobes. You can also drill into the adobe walls before the jambs go in, fill the hole with cement mortar and fit a threaded anchor bolt into place two or three on each side. The heavier jambs don't have to be attached to the wall if they are firmly attached at the bottom and to the lintel. If you plaster the walls, the metal lath or stucco netting can be attached to the back or sides of the jambs and the plaster will do a fine job of attachment. We have an adobe discussion and support group that might be useful to you. You can join us at adobe-subscribeATyahoogroups.com

Q: We have purchased an adobe home built in 1945. We would like to put up curtains. Over some windows there will be three curtain rods. Is there anything special we should do when putting the screw and/or nail in the adobe wall?

A: Sometimes you are lucky and there is a wood lintel over the windows and it will be just behind the plaster. Sometimes you are really unlucky and it will be a concrete lintel. Sometimes it is just adobe where you want to put the rod holders. In that case gold deck screws about 4 inches long work best. It might help to pre-drill an undersized hole but sometimes the deck screws go right in. Deck screws have a large, aggressive thread that gets a good bite in adobe. The longer length allows them to get deep into the adobe bricks where they will hold well. We have used them to mount handrails for stairs and kitchen cabinets. You will need a strong drill with a Phillips bit to drive the screws.

Q: I have an adobe home in Durango, CO which is experiencing moisture and rot in the wood lintels. There does not appear to be any flashing over the lintels so it is hard to say if the moisture is coming from within or the outside face. What do you recommend for filling voids (epoxy?) or for rebuilding removed rotten wood (auto body putty?)?

A: Epoxy is better, auto body putty is easier. I think one exp oxy formulation is called Git Rot and is just for replacing rotten wood. If the lintels are exposed on the outside, then it is time to think about covering them. If not then it would be good to sleuth around to try to find the source of moisture. Lintels in adobe walls should be forever.

Q: I have a 1950s adobe home with a conventional roof and bricks that appear to have some mortar in their composition. Since the overall look of my home is sort of ranch style, (not Santa Fe style), I would like to stucco the outside for a uniform look, while preserving the raw brick appearance of the interior of my house. Anyway, I was hoping that since my roof overhang provides ample water protection, I wouldn't have to worry about trapping water between the stucco and the bricks. Any advice? By the way, I live in LA and was thinking of laying extra thick wire under the stucco to give my walls an extra measure of strength against quakes.

A: Your plan sounds great to me. You might gingerly ask around local building officials or seismic experts to see what they think about your use of stucco net. It is good to have and is part of the normal stucco routine. I think it will provide some seismic resistance.

We had a paper by Marcial Blondet of Peru at AdobeUSA 2007 in May talking about the use of polypropylene netting under stucco for the seismic reasons. The Peruvians have a large Dutch shake table dedicated to adobe construction at the Catholic Pontifical University of Peru in Lima. I consider them to be the leading edge of world earthen seismic knowledge.

The wire should work just as well. If you can connect it to the foundation with masonry nails or screws and then make contact with the bond beam or wood plate under the roof system, then all the better. You will have created a nice tension path. That is a word that warms the heart of the seismic pros in California.

Q: I seem to have water with salt going up the wall which is causing the adobe to loose consistency and starting to crumble. I tried to lower the level of the floor in the areas close to the wall and that seemed to help a bit. I used a lime wash on the wall, and not any kind of plaster. Can you help me?

A: My experience is that over a long period of time, the ground level around a house tends to rise. This means more adobe wall is in contact with the surrounding ground and that there is more contact surface to transmit moisture into the adobe. If you lowered your floors and had success, then if you can remove earth to lower the exterior ground level also then that will also help reduce salt transmission via the moisture. The house might have a stone foundation (plinth) and the surrounding earth has risen to a level above the foundation so moisture can move directly into the adobe. A stone foundation is usually a very good way to stop the upward migration of moisture which is driven by capillarity.

Since the salt is delivered by water, anything you can do to reduce the level of moisture around the house will slow the process. Moisture may be coming from roofs or nearby areas that have been paved with asphalt or cement or even hard packed earth. If this is the case, then a channel might be excavated to remove rain runoff to an area at some distance from the house. Here in New Mexico we try to create a swale which is the opposite of a berm. The swale insures that next to the wall, the ground slops down away from the wall so that there is no standing water to percolate into the ground. The roof might benefit from gutters to catch the rain and keep it from entering the ground.

Worldwide, from New Mexico to Mexico to Argentina to Germany, I have seen people create a vertical 8 to 20 centimeter thick concrete wall protector against the adobe. It often looks as if it were an original concrete foundation so I call it a pseudo-foundation. This almost always has a negative effect and actually keeps moisture in the wall from being able to get out. The salt laden rising moisture then appears just above the concrete creates its damage there. Also, at the top of the concrete if there is any little opening, then rain that hits the wall moves down behind the concrete and so the protecting device becomes a funnel to move moisture into the wall. The recommendation is to use just earth plaster or lime on the exterior of the house and consider it to be a sacrificial layer and renew it from time to time.

The damage that you see may not be very deep into the wall. You can use a small trowel to excavate into the wall to see how far the deterioration goes in. Up to 8 or 10 centimeters might look terrible but is not an overwhelming structural problem. Just excavate out the deteriorated wall and replace it with adobe mud that is as close to the original composition of the wall as possible.

You might also consider digging a trench, canal, around the house considerably lower than the bottom of the wall and foundation. The bottom of the trench can be filled with gravel and a perforated pipe. Some of these new perforated drain pipes have a fabric over them to keep out dirt and fine sand. The pipe should be installed to always slope downward to the lowest point and then may be conducted to a lower point on the property where it can emerge above ground. Europeans have done this sort of thing for years using clay draining tile. This system will work by gravity. If the conditions around the house do not permit gravity to work, a large collecting basin, called a sump, can be installed at the lowest point and from there can be pumped away from the house perhaps to a neighbor you would like to annoy.

I do not think there is any magic chemical that will bond the deteriorated adobe together. Adobe seems to have resisted all attempts to apply modern technical solutions with only very few exception. Mud to mud, earth to earth seems the best remedy.

Situations similar to yours have been addressed at many of the international earthbuilding conferences that have occurred in the past 10 years. There is much further information in the professional literature and in conference proceedings.

Q: For how many years does a house built of adobe with a roof garden and no beams stand? Is it a advisable to adapt that idea here in the Philippines?

A: If you have no roof beams then I assume you might be thinking about an adobe dome or vault. In that case adding the roof garden would add the risk of the slightest leak  being detrimental to the earthen dome. I don't think the two go together but with a super watertight membrane between the dome/vault and garden you might be able to prove me wrong. People have done that.

Q: Have you seen any homes built using adobe walls and plywood over wood frame floors?

A: If you mean that the adobe wall would be on top of the plywood floor with its weight bearing on it and the frame, don't do it. Adobe is very heavy and needs to rest on a very sturdy foundation. The floor system can be suspended from the side of the foundation on a ledger. Or there can be a step on the interior of the foundation to which a pressure treated plate can be attached for the floor frame.

Q: I live in a house with termite damage; it has been professionally treated, but a 6 foot section in front needs to be totally redone. I was wondering if is there any way to build the front of the house with adobe, and the rest adobe over the existing house...like, take the siding off and put adobe outside around whole house? Can an adobe wall replace railroad ties? I mean are they strong like railroad ties ?

A: Adobe walls need a substantial foundation. Termites usually do not bother adobes but in some climates they have been known to eat the straw out of the adobe. I rarely use straw in making adobes anyway. An adobe wall can certainly replace railroad ties and I would personally want to do that. Most old railroad ties were treated with creosote which I would not want to have as a part of my home. You can build adobe walls around the perimeter of the house if you dig a trench and fill it with concrete or even gravel to create a foundation and spread the load.

Q: We just moved into an adobe house and have bought shades. We now realize that these shades attach to the top of the window (horizontal surface above the sill), not the sides (like most blinds). Blinds and shades take such abuse being pulled up and down that I am worried about how to attach them. Do people just use anchors and gingerly pull the shades up and down or do they just not buy shades when they have adobe walls?

A: There has to be a lintel over the window and door openings in your home. It will be a wood beam or concrete. Concrete is rare. So if your luck holds out, all you have to do is drill upward through the plaster with a small diameter masonry bit until you hit the wood. Then find screws that are long enough to get at least an inch into the wood. If the lintel is concrete then there are several systems of specialized drill bits and specialized screws that can attach to the concrete.

Q: I live in Hawaii and would love to have a natural, eco-friendly home. Concerns in my state would include high heat, termites and earthquakes. What kind of home would you suggest? Could an adobe home be reinforced with steel?

A: Adobe is perfect for high heat and with little added straw, termites are not interested. As for earthquakes, if you have a good foundation and a good bond beam at the top of the wall to tie it all together, the adobe construction system can withstand seismic activity to some degree.
Most of the California Mission Churches are standing after all the earthquakes.

Q: I forgot to mention that hurricanes and heavy rain are also a concern.  What would be the best kind of natural home for Hawaii?

A: Naturally, I think adobe homes are the best solution for any situation. It might not be a bad idea as a second opinion to look at the type of housing used by the various populations of Hawaii before the arrival of the Pilgrims. Autochthonous usually trumps anything else, but since I have never been to Hawaii and now that I hear there are hurricanes and rain may never make it, I don't know what the original housing might have been like. As I think about it, earthquakes, hurricanes, heavy rains, burning stones, it sounds a bit scary. I hope at least that you don't have snakes and spiders or tsunamis.

Q: What are the possibilities of retrofitting an existing home using either adobe or rammed earth? The home that is being retrofit was constructed with wood, and I am interested in using more sustainable materials to provide additional insulation.

A: Adobe construction and rammed earth can easily be retrofit to other types of construction. They require extra heavy duty foundations and making connections between earthen and wood walls is a matter of having some rebar or lag screws or bolts or heavy duty plaster lath to connect the new construction to the old.

Q: I want to attach a flat screen television to a plaster covered interior adobe wall that is 12 feet high. The tv weighs 120 pounds, the tilt bracket weight 35 lbs. The tilting of the television will cause some horizontal pull of any anchor I use. Can I safely use 6 to 12 concrete anchors, the kind that expand as the screw is inserted. Will their insertion into the adobe break down the adobe or is the wall be stable enough from the plaster on both sides and the weight of the adobes above? Is there a better way to do this?

A: The concrete anchors will not work unless they go in at least four inches into the adobe. Even then, they may burst the adobe in the middle of the brick due to the extreme pressures they can exert. We have had great experiences with gold deck screws of the four or four and 1/2-inch length. They have large, aggressive threads throughout their length which will get a strong bite in adobe bricks. The six-inch screws have threads only on the end so I don't think they are any better. It is a good idea to pre-drill a pilot hole the size of the shaft of the screw. These screws will provide surprising anchoring power. We have one adobe dangling on a wire from a scaffold with one of these screws in it. Six to twelve of these should be all you would need. I have hung a stair rail with these screws where all else had failed from the constant use.

I often do not drill a pilot hole but if there are several screws within a foot of each other I do it since who knows when an adobe brick might split. Bricks from New Mexico Earth almost always are uniform in having fairly fine granules. Some adobes will have larger pebbles or stones and are more likely to split. Drilling discovers those stones beforehand.

If you still feel nervous about the mounting, you can drill through the wall and use 1/4-inch all-thread rod. Put a 3x3-inch plywood washer under each nut and metal washer on the opposite side of the wall. Carve out enough space on the opposite side so that they can be plastered over to hide their existence. Then the only thing to threaten the existence of your TV will be the next big thing that comes along to make it all obsolete.

Q: We are thinking of purchasing an old adobe home for cheap, mainly because last winter the pipes froze and flooded the kitchen and bathroom. Unfortunately, this was not caught quickly. The walls are still wet in some areas and there is cracking around doors, the floor is swollen and needs to be replaced, there is some mold in corners and the plaster has swelled in areas and is breaking off. How feasible is it to fix such an issue?

A: This happens all the time to buildings adobe and otherwise. We just saw the beautiful old Chicago Motor Club building just off Michigan Avenue with all its windows dripping water inside from water in the basement.

We looked at a house in Hatch, NM that was flooded in August of 2007. It will recover. As long as the walls are still standing there is hope. Plaster can and should be removed up until dry wall is found to help dry the walls. Then it can be replastered. Most molds can be dealt with using bleach first then 20-Mule Team Boraxo as a dusting or light spray. Some molds are the kiss of death and need professional remediation. That is not my area of expertise. Renovation and repair are always difficult. The old salt says:" Get estimates from three reputable builders. Add the three estimates and you will have the actual cost."

Q: I am designing a small house to be built in Torrance County NM. It will be passive solar design, post and beam, with light straw clay infill for exterior walls, adobe floor. At least two major walls on the interior are to be 10" thick adobe brick wall. These are in the south rooms of the building and will serve as solar mass. These are non bearing walls. One runs parallel to the roof trusses above. This connects with the south exterior wall. The other will be midway beneath the trusses, and will run perpendicular to them. Loading, however, will be on adequate post and beam structure for that wall.

A: Adobe, as it turns out, is the most capable load bearing wall of your various types. It can handle around 3000 pounds per linear foot with a safety factor of six, as I remember. Some thought needs to be given to anchoring the adobe wall at the top so that it does not flop around in a breeze or seismic event.

Q: How do I find out whether an adobe house built in 1947 was engineered to withstand an earthquake. The house is one of 16 adobe houses built in Sleepy Hollow area of San Anselmo, in Marin County, CA. I would love to know more about the builders at that time, and what concerns an insurer might have.

A: I really doubt that any type of house in California was earthquake engineered in 1947. Adobe, certainly, did not get anti-seismic attention until the 1970's when Fred Webster began to use the shake table at Stanford to study them. If a house had a decent foundation and a good bond beam then it can be expected to handle many sorts of smaller shakes. If there are good, solid corners without window and door openings any closer than four feet from the corner and if there are lots of solid panels of adobe in between the windows and doors then the walls will have reasonable shear resistance. Additionally if the roof system is properly built and well connected to the walls, it acts as a diaphragm and adds even more resistance to the walls.

There has always been a surprising amount of adobe construction activity in California but I am not up on my history for your state. Precisely what insurers would be looking at is also beyond my experience. Besides Fred Webster, Bruce King is another engineer with considerable insight into adobe construction and how it fares in shakes. Both can be googled. There also must be adobe expertise  right there in Marin County due to the history there.

Q: I have a "newer" house that is half adobe and half is frame build. It is about 30 years old. I need to build an addition to the house. I am thinking of using adobe for the addition. The addition will be placed against the point where the frame half meets the adobe half. Accordingly I have to tie-in the adobe addition to both the existing adobe wall and to an existing frame wall. How do I tie-in new adobe wall the existing construction -- both older adobe and frame, in this case? Are there generally accepted methods, are some better than others?

A: The best way to tie adobe to adobe is to remove stucco or plaster and chisel out a half adobe from every second or third course in the existing wall. Adobes from the new wall can then be "sewn" into the existing coursework.

It is equally or more important to tie the foundations. This can be done by drilling into the existing foundation six-inches and epoxying two or more half-inch rebars that will extend into the new foundation. Occasionally, when desperate, the new foundation can be poured to form a "y" around the existing one.

The bond beam is another important place to connect. If the original bond beam is wood then various screws, lag bolts, thick metal plates or even a chiseled mortise and tenon joint can be used. If it is concrete then back to the drill and epoxy technique or arrange to pour the new bond beam on top of a section of the old.

The adobe to frame connection is accomplished by using half-inch all-thread rod to bolt through a double stud through the adobe at three points up and down the wall. Use a 3x3" backing plate of 3/4" plywood on the out side of the adobe wall - in a notch so it can be finished flush. A single stud will do if a double is not available. Gringo blocks can be placed in the adobe wall and long screws or lags into or from the frame wall will hold it all together.

Almost always there is some slight or not-so-slight cracking between the frame and adobe wall. This is a good place for a flexible, paintable caulk or a trim strip of wood.

Q: I'm considering buying property in Jarales, NM which has 3 dilapidated adobe structures on it and am wondering if they can be renovated. The walls are standing, with cracks but the roofs have fallen in.

A: Financially it makes sense to restore a building if the structural parts of the roof are intact and do not have to be removed. Sometimes there are other reasons to save a building: historical or cultural considerations, family connections, just plain falling in love.

Q: I am interested in purchasing a "burnt adobe" house in Tucson. It was built in 1960. The lot is flat and level. It has a large crack on the cement floor, and several large cracks in the walls. Most of them are at the tops of the interior walls where they meet the wood beams, or cracks in the corners right where the two angles meet. In some places it is a stepped crack following the courses of abode for three or four rows. The roof is pitched and does not appear to have any moisture problems. My question is: Is this the kind of crack that signifies serious structural issues, or are these natural cracks in adobe that we can patch with a minimum of time and money?

A: Chances are that the quemados were made in Sasabe, Mexico not to far over the border. They made kilns with a vault of unmortared adobes stacked loose. Raw adobes were placed inside and then a huge fire was built at one end and the flames and hot gasses went down the kiln to a chimney at the other end. It took a 5-ton load of firewood brought in on a flatbed truck and the firing lasted three or more days. Like the Romans, the Sasabeans were denuding their surrounding hillsides of trees and had to go further and further away to get enough fuel. I think the system lost its economic feasibility around 1975 just before I had a chance to see it in operation.

Once the firing was ended the vitrified adobes were removed. They were reddish/orange and clinked just like a standard brick. The adobes that had formed the vault were then stacked to be the next batch to be fired - a very clever technique on the part of the Mexicans. Quemados were waterproof to a large degree but the firing was not enough to make them resistant to freeze/thaw cycles so some deterioration would occur especially at the top (rain and snow) and bottom (rain backsplash or rising damp) of walls. In many cases they were used as a coping on the top of a raw adobe wall to stop moisture incursion from rain and snow.

Quemados usually test higher in compression (about 550 psi) than their original raw form (about 300 psi) but I don't have any numbers around to substantiate that item of memory. That might be a bit more information than you need but it helps explain some of my intuitive thoughts regarding Gregg's Spanish system.

If you are seeing wall cracks under the roof beams, that could be a sign that there is not a bond beam. Most masonry (adobe, brick, concrete block, stone {and the second top plate in a frame wall} wall systems rely on a bond beam of wood or concrete to spread the load of roof beams across the entire wall and also to provide an anchoring point for the roof system. If cracks are stepped and following the mortar joint, it is an indication that the quemados are stronger than the mortar material. If the floor is cracked there might have been some movement of the structure due to the heavy load of the burnt adobe walls. The house is fifty years old. A little movement is acceptable and the question is how much that might be. If there is no bond beam it is not a fatal flaw but some thought might be given to the situation. Again, this could be a case for Higbee.

But my best guess would be to stuff a mortar mix that is as near to the original mortar into the cracks. Then watch the house for the next decade or two to see if they reappear. If so, fill the cracks again and repeat the watching. That's what I do with my house.

Q: We are in Colorado and use the new Mexico adobe building code. If I am making a two story addition, how thick does the brick need to be on the bottom? Do we need to get a engineered foundation?

A: The NM code specifies that the minimum for two-story construction is 14-in thick walls for the first floor and 10-in thick walls for the second floor. Should you want both walls to be the same thickness, then 20-inch walls are required. As long as the footing gets down to the frost line, is 8-inches deep and 4-inches wider than the stem wall on each side (That's the Q-rule and PG McHenry Rule since the Code only requires 2-inches each side), has two 1/2-in rebar with a stem wall the same width as the adobe wall it supports that gets 8-inches above grade and 4-inches above floor level then no engineer stamp is needed in NM.

Q: I m a student of architecture and my thesis topic is earth mud construction, so I want to ask what are the structural considerations and limitations like height, length and breadth of the room?

A: The aspect ratio for the height of adobe (earth mud bricks with earth mortar) walls is 10 in most codes in the United States. Wall heights can be ten times the thickness of the walls. They should be tied together at the top with a bond beam, sometimes called ring beam or collar beam or tie beam. This beam could be concrete with reinforcing bar or it could be wood or bamboo lashed together. The beam ties the building together at the top, spreads the load of the roof and gives a base for attachment of the roof structure.

The State of New Mexico allows two-story construction if the first story is 35 centimeters in width topped by a bond beam and the second story is 25 centimeters in width topped by a second bond beam. If a designer wanted the wall to be the same width for both walls, it would have to be 50 centimeters. Lateral runs of an adobe wall can be 8- to 10-meters in length before they terminate, or turn a corner or intersect another wall or buttress/pilaster.

Distance between walls that support roof structures is governed by the type of roof structure material available and the spacing of these materials. In New Mexico, traditional adobe structures were often no more than four meters in width due to the availability of small diameter trees which were used to support the roofs. In modern times with wood I-beams and steel I-beams and truss systems, larger spans are possible up to about 10-meters. Lengths of rooms can be as long as one wants as long as buttresses, pilasters or intersecting walls occur at 10-meter intervals or less.

Using domes and vaults, earthen roofs can be built easily to five meters in diameter or width. Experienced masons in Arabic and Asian cultures have built to ten meters. In New Mexico, adobe buildings serve as homes, churches, schools and government buildings. In Sanaa, Yemen masons have learned to build ten-story buildings of earth.

Can you tell me or send me the details for a building of 4-5 stories high?

In the United States we are only permitted to build two stories in height by the New Mexico Earthen Building Code. The International Building Code now has a section on adobe but also limits height to two stories. To find the details of 4- or 5-story construction will require help from Yemen. I think that is the only place on the planet now building to that height. There are some 4-story buildings in Germany and France probably built in the 1930's or earlier.

Q: The main walls are about 600mm thick. The old roof is currently bearing down on the wall with little or no plate and so are the main old wood beams. I want to put a concrete bond beam to cap all the walls ready for the new roof. The width of the beam I presume will be 600mm but I wasn't exactly sure of depth and rebar specifics.

A: The New Mexico Earthen Building Code would require a concrete bond beam to be a minimum of 500mm wide by 150 cm in depth. That gives room on each side for a 50 mm piece of wood to hide the concrete and/or act as the form for the pour. I am doing some interpreting. Up to 350 mm width the bond beam has to be the width of the wall but wider walls can have a somewhat narrower bond beam than the full wall width.

The Code would require two #4, 1/2" or 12 mm diameter rebars. I would recommend three suspended at the 1/3 point from the bottom of the concrete, one at the center and two about 40 mm in from the outside edges of the concrete.

Myself, I always built wood bond beams which are allowed by the code sized the same as the concrete. Code allows it to be built up in layers of overlapping boards as thin as 25 mm. It's so much faster. It's so much easier. Then, it's easy to bolt, lag, spike, screw the beams, vigas, roof parts to the wood bond beam where ever needed without having to figure the locations for anchor bolts before hand.

Here at Northern College we have an experiment in progress to measure the ability of a wood bond beam to stick to the top of the wall in comparison to a concrete bond beam's ability to stick. The walls are built. We await warm spring weather to hook up to the overhead crane.

Where is your building located? It sounds intriguing.

The house is in northwest Bulgaria, about 30 minutes from the Danube river. I think you will be fascinated by the extent of the use of mud brick throughout Bulgaria. When I arrived I also had no idea as to its abundant use here. I come from an architectural/engineering background, but this is all pretty new to me as you can imagine. The history is sketchy, but I’ve been told the house is around 75 years old. It has a stone and concrete foundation. The exterior walls are about 600m thick with internal 300-400mm. The render is a lime and sand type affair maybe with cement I’m not sure. Chimneys are mud to roof height and still function brilliantly.

I'm pretty sure I'm gonna go with your composite wooden bond beam idea.So if you have more details on that I would be most grateful.

I am stunned. What a surprise to be stunned. I know that there are on the order of two million earthen homes in Central Germany so I was prepared to say "yes, of course" regarding the Bulgarian adobes. But they are so beautiful and largely intact. Your favorite house is my favorite, also. The doors, windows and details on all the houses are beautiful. It appears that most have been spared the indignity of cement/lime stucco and are plastered with mud or lime based plasters.

Heres another picture I found this morning to wet your appetite.

Q: I live in an adobe home (stucco exterior, plaster/other interior, metal roof) built in 1931. We had the windows replaced 5 years ago, but did not pay for custom framing, so all the windows were retrofitted into existing openings. We're finding that most of the windows have water damage because of incorrect maintenance. On one window, water damage had come through to the interior of the house and had been continuously covered and not corrected (before our purchase of the home). After removing cover-up work, bad caulking, etc., the gap from front to back on the exterior of this particular window, and directly under the window casing, is quite deep (at least 6 inches). Up both sides of the window, moving from the bottom, is also gapping at about 2 inches deep. Now that the loose stuff and cover-up or incorrect material has been removed, and the adobe bricks and original wood supports visible, what is the best method in filling these gaps? Concrete, plain ol' mud, stucco with diamond mesh? Also, should a vapor barrier be used? What kind? We want to do this right so that more damage does not occur!

A: Yipes! I am sorry to hear of your problem. Adobe mud is probably the best way to fill the large gaps. Once it is dry you might be able to work from the outside to improve the air and water tightness. Without being able to see the windows, my first suggestion is to consider polyurethane sealant foam that comes in a can. You should use the formulation that specifically says it is not highly expansive. I just went out to my shop but cannot find a can of the brand I use and cannot remember the brand. The highly expansive foams can put enough pressure on your new windows to hinder their ability to open and close. These foams are a vapor and moisture barrier. The polyurethane is the primary constituent in Gorilla Glue so have pity on the person who might have to remove the windows in the future.

You might take a look at the possibility of inserting a metal eyebrow flashing at the top of the window to move rain out and away from the window. You might even cut a horizontal slot with a masonry blade in the stucco above the window and insert the flashing into the slot filled with silicone or butyl caulk. That slot is called a reglet and is often employed in retrofit situations for windows or new roof lines abutting a wall.

For a totally different approach, you might be able to glue or staple a house wrap such as Tyvek to the flange of the new windows, if they have a flange. Wrap that over the wall about six inches beyond the window on the sides, top and bottom then use expanded metal lath and stucco over the lath right up onto the window flange. There are probably twenty-seven other ways to fix the problem.

Q: We want to turn a window into a door on an exterior wall of a 100 year old adobe house. Is that possible and just how do we do it?

A: You are among the world's luckiest people. We assume there is a lintel spanning across the opening of the window to support the load of the wall above. Then, to keep the luck going, we hope that the door does not need to be any wider than the window. Or at least not more than 3.786 inches wider. The lintel has to retain sufficient bearing surface on the walls. More luck means that the top of the window ( or bottom of the lintel) is high enough to accommodate the top of the door.

If your luck has held this long, then all you need to do is remove the window, chop, whack, saw, chisel, chip the adobes out from below it down to floor level. There might be electrical cable or water pipes in the adobe so remain alert. If need be you can rent one of those high pressure water saws that they use in stone quarries to cut stone. It has never been done on adobe but this would give you a fine topic to present at www.earthUSA.org

If there is room, build a rough buck of 2 x 6's which has the inside dimensions to match the required rough opening of the door you want to install. The rough buck is meant to serve as does the rough opening framing of a door or window in those other sort of houses. The rough buck can be attached to the adobes with big long screws. I use some called Timber Tek. They have a hex head and come in lengths from 3- to 14-inches. Three or four on each side will do just fine. Four-inch long deck screws will work, also. Then the door jamb is fit into the opening according to the manufacturers directions. Some modern doors come with a flange that fits on the outside surface of the rough buck and is screwed in place in a couple of minutes. Other door jambs go in the old way with shims and screws and careful use of a 6-foot level. Just in case you are not using a pre-hung door, make your rough bucks out of 3 x 8's or doubled 2 x 6's, put them in place and fit the door directly to them.

Hope you still feel lucky. If the door is wider or higher than the existing lintel, then that my friends is an entirely different story.

Q: We have a house built in 1935 with substantial adobe walls. Recent burglaries have moved us to consider "rejas" protecting the windows from intrusion. Would the screws you referred to called "Timber Tek" work for us? Would we need an epoxy to facilitate an anchor system?

A: I think 8- or 10-inch Timber Teks will work. You do have to make provision to be able to open the window and reja from inside any bedroom and perhaps some other rooms in order to get out in case of fire or other inside generated emergency. You might consult with a professional security installer to get up to date info on which rooms require egress. If Timber Teks seem less than desirable, we have drilled all the way through and used all thread rod to fabricate a bolt that has a 4" by 4" 3/4" plywood washer on the interior. It requires some digging into the interior side of the adobe wall and then plastering over the washer and nut.

Q: I have just finished my architecture studies in the UK, and am now in Egypt to start work on the restoration of a 1920's mud brick building (the University of Michigan's former dig house). The building was constructed in Fayum on the edge of the Oasis, so an arid sandy environment. There are no foundations, and many of the walls are now failing at the corners, leaning over and currently propped, or have collapsed altogether. I think the foundation issue is the first to deal with, followed by the walls. I am aware of the option to either underpin the building and create new foundations, or to inject the underlying soil to stabilize it. The walls could then be reinforced with timber reinforcements at the corners, a continuous ring beam (also timber?), and possibly wire mesh used to reinforce existing walls and then rendered overtop. I would like to know any suggestions you might have, as I have not worked on this type of building before.

A: I am not sure that a foundation is necessary as we find many earthen buildings throughout the world that do not have a modern-day recognizable foundation. Certainly providing a stable base for the building is the first step but there are lots of ways to do that. A wood bond beam would definitely be in order but I am not sure about timbers at the corners. I usually favor adobe solutions to adobe building problems rather than borrowing elements from other construction systems.

Q: I want to explore the limits of adobe on number of floors and openings with the usage of 21st century materials in order to not be considered a dogmatic ecologist. As I said the limits of adobe: How big openings/windows can one get with the use of metal or some other materials that can help me expand the traditional limits of adobe? Also I want to know how adobe reacts along with other materials like metal or concrete (ie metal beams rather than wood or concrete inside the walls for better stability or metal mesh on top of the adobe wall finish nailed in for structural support etc.) If you also know some other techniques with which I can achieve my goal of expanding the traditional limits of this amazing building material, please let me know.

A: Adobe has an aspect ratio for walls of ten: wall height can be ten times the wall thickness. In the United States, by code, one story construction needs a minimum of 25cm wall thickness. Two story construction may have 40cm below and 25cm above or both stories need to be 50cm. Actual limits of adobe construction can be seen in Yemen where there are 9-story buildings. Walls are thick and windows are small at the bottom. Walls are thinner and windows are larger at the top.

US Code requires 70cm columns between window and door openings although I would personally mandate 1-meter. Additionally windows and doors should be no closer than 70cm (Code) or 1-meter (Quentin) from corners measured on the interior surface of a wall. Window and door openings can be as large as you want as long as the lintel that spans across them is sufficient to carry the load above. Lintels can be wood, concrete, steel, stone, bamboo, cactus ribs, and anything else that can be made to bridge across and opening.

Steel, concrete and plastics work just fine with adobe and are often incorporated into modern adobe structure in New Mexico, Brazil, India and Korea to mention just a few places. The holy grail to be searched for is a treatment of the tops of exposed exterior walls, parapets, where moisture is a problem to halt or slow the erosion of the walls. A traditional solution is just to get out after every rain or once a year to replace missing mud.

As far as I know, there is no known use of 21st Century materials that has allowed adobe structures to surpass the Yemeni techniques. The buildings are all done with adobe, stone and a minimal amount of wood poles. Don't let that stop you from looking. I would be happy if you were called a dogmatic ecologist. Someone has to stop the madness.

Q: I have an existing adobe home that I would like to remove a wall between two rooms. Adobe wall of course. The main roof runs parallel and the other roof ties into the wall to be removed. I was thinking rough sawn wood beam. I can support both roofs while placing this beam below the vigas. The question is, on the exterior wall that one end of the beam will rest on, what type of buck or pilaster should be used. I know I can not set it in the existing exterior adobe wall. The new opening span will be about 16 feet. Any thoughts or suggestions would be great.

A: It sounds as if there will be considerable weight on the new rough sawn wood beam if the opening is 16 feet. At the end on the exterior wall you might consider a wood or concrete post (pilaster) that would pierce through the floor to put the weight on a concrete pad on undisturbed soil. Best of all, see if you can find a local engineer or architect who would take a look and figure appropriate sizing for the beam and post or posts.

Q: I have designed and will be building a new Sala for a permaculture school in Chaing Mai, Thailand in 2013. We will be using adobe bricks made with a mixture of clay, sand and rice husks. For speed of construction and financial constraints I have opted for a metal roof over steel scissor trusses. My question: What is the best way to fasten the scissor trusses to the adobe walls? The walls will be two bricks wide so will be about 16" or more thick. For floors we have embedded iron wood in the walls and then the floor joists are attached to that and then cobbed in. Do we do the same with the steel trusses.

A: Iron wood would work nicely if it can be arranged to form a bond beam that runs continuously around the top of the building. This is sometimes called a ring beam or collar beam but the purpose is always to spread the load of the roof and provide a point for anchoring roof support members. The thickness should be at least 5cm but better would be a scheme of two 5cm layers which can be lapped at the corners to make really strong corners. It should be at least 25 cm in width and placed so that it bridges across the two widths of adobe. 40 cm would be even better as it would cover the two widths completely. If ironwood is hard to come by in such volume, bundles of staggered bamboo has been known to work just fine.

Now, so that the light weight roof structure does not lift off in a wind, it would be good if not imperative to have a couple more courses of adobes on top of the bond beam between the scissor trusses. You might want to think of some way to isolate the steel trusses from the adobe and any cob used since earthen materials can have a bit higher moisture content than is desirable for contact with steel. You might also want to think of some sort of a tension path from the bond beam down to the foundation. That could be done with wood strips, steel straps, nylon straps such as used to bind loads on pallets, bamboo or rebar. It can be embedded in the wall if there is a continuous cavity between the wdiths or it can be on the interior or exterior surface. Perhaps the weight of the adobes above the bond beam will be sufficient. I just don't know about your weather conditions.

Having had some experience with a tin roof over my head in the summer heat, I can't get to excited about the thought of direct sunlight raining down on the roof. Any insulation you can think of will be worthwhile: reeds, grass, fiberglass, layers of woven floor mats, thatch, thatch without the tin, bamboo bundles, ...

Q: Have you ever seen or built or designed an adobe building that had cantilever extensions of rooms or spaces that are on the second storey? I know that adobe has a powerful compressive strength, but can a cantilever be built and made from adobe? If not from adobe, can the cantilever extension be built from the supportive wood on the roof and have like a hang, in front of the building from which we can built upon?

A: Adobe does not do well in a cantilever situation unless very small steps are taken at each course. To cantilever out 12-inches would require about six courses of 2-inch cantilevers and six courses is 24-inches. Then there would be an overturning moment that would try to have the adobes roll over and drop.

Perhaps a cantilever with beams that are sized appropriately for the load and the lever arm of the cantilever and a counterbalance at the opposite end of the beams. There are cantilever schemes and calculations to be found in timber frame handbooks. Try to stick with adobe and perhaps keep your walls in a straight vertical line which makes it easy for the first-time builder. Do a second story on your third building and a cantilever on your tenth when you will really have a feel for the material.

Q: When building an adobe home, is it necessary to install gringo blocks and rough bucks? Is it possible to somehow leave an opening and only use Lintels on top and maybe screw the door frame directly into the adobes? I am planning on leaving the adobes exposed inside and out, and don't want the gringo blocks visible.

A: Sure. I did it. Once. We used 4" x 10" door frames so that we did not have to worry about their warping over time. The door frames/jambs went in first and we anchored them to the foundation and as the wall went up used steel straps in the mortar joints attached to the back side of the frames/jambs. We left a finger's width airspace at the top of the jambs before the lintels went in to allow for any settling of the walls. Filled the gap with fiberglass insulation and put a little trim board over it. Screwed some long lag bolts through the top 4.x 10 into the bottom of the lintels. The exterior doors were custom built, three inches thick. It took me a while to fit them into the jambs and mill and attach the door stops. Hinges of course were oversize. Doors slam and doors of this size exert a ferocious impact force on the jamb. Hence the 4x10's. The interior doors were 1-3/4" standard exterior panel doors and were a bit easier to fit into the jambs. The windows were Hurd. At that time the standard wood frames that Hurd used were nearly the equivalent of 2x 6" clear fir. They screwed directly into the adobe walls with 4" or 6" deck screws. Windows don't experience the impact forces so it is simpler.

Later projects we went back to solid gringo blocks downsized a bit. Then we could plaster over them and tool them to look like the other adobes. Rough bucks are part of the High Speed Fast Moving Don't Look Back System Using Speed Leads wherein the rough bucks are set up before the walls go up. Then the adobes are laid to the string and bump up against the back of the door and then window bucks saving the mason having to painstakingly create each opening straight and plumb. This could work for exposed adobe walls. If the rough buck is 2 x 6 and the door jambs and window frames are made for 2 x 6 walls then a trim strip can attach to the jamb, held back 3/8" and scribed to the adobe to cover the buck and the finished product looks good. It also preserves an airspace between the bucks and the jambs where the shims go and by removing the trim strip access is available to the shims at a later date if the door jamb needs to be adjusted. I always use screws rather than nails when attaching the rough buck to the gringo blocks and the door jambs and window frames to the rough bucks. That allows changes or adjustments later.

Q: I am living in a adobe home with 16" walls, built about 50 years ago in Tucson, Arizona. I would like to add a porch to the front of the home. How could I anchor the porch to the wall?

A: Possibly there is a bond beam in the wall just under the interior vigas or beams. If it is wood, long screws through a ledger plate will anchor the ledger plate to the wall and the porch structure can be attached to that. In truth it should just be called a ledger but lots of people add the "plate." If there is no bond beam then you need to drill through the adobe wall and run all thread through the wall and secure it on the inside with with 4" x 4" plywood with steel washers on that and then nuts and steel washers and nuts on the exterior. Probably about every three or four feet. This can all be chiseled into the wall and plastered over to hide them. The ledger should be two or three inches thick and have a depth equal to the depth your porch roof support members which can be attached to the ledger with steel joist or beam hangers. The joists or beams can also be placed on top of the ledger.

Q: We are thinking of purchasing an Adobe home in Cave Creek, AZ. The lintels above the sliding glass doors (x 4) and the windows in the front of the house (x 3) have extensive termite damage and need to be replaced. How difficult is this going to be to get done, how costly do you think it will be?

A: It is not difficult. Remove half a lintel from one side with saws, chisel, hammer, gumption. Slide in a new half lintel and tap in shims and/or damp dirt mortar to take the load of the adobes above and transfer the load at the ends to the wall below. Go to the other side and remove that half and replace it. Then drill through both halves every sixteen or eighteen inches and bolt together will 3/8" or 1/2" all-thread and 1-1/2" washers. You might want to bore or chisel out a pocket to hide the washers and nuts and then fill with wood dough. $150 to $300 labor per lintel plus the cost of the new beams. Normally termites do not get wood that high in the house but everything in Arizona these days seems to operate at the extremes. Consider a non-toxic treatment such as borate based salts.

Q: I am planning an adobe wall. My question is if I have to include the stem wall height in the wall height used for calculating height/width ratio or just the adobe part? Say my wall is 0.3m thick, I can build the wall 3m high. Do I count this 3m from outside floor level to top or from top of stem wall to top?

A: As best as I can understand the New Mexico Earthen Building Code, the height to thickness ratio applies to the adobe wall from the top of the stem wall to the bottom of the bond beam. Wording of the Code varies over the years. A clever person could use this interpretation to achieve a higher ceiling level. I personally used the ratio to figure the total distance between the floor and the bottom of the vigas or beams. The ratio also applies to cob and rammed earth although many rammers operate more in the range of 6 to 1 height to thickness ratio.

Q: The front of the house has planters with dirt at the brick wall with evidence of 1-2 inches of coving, should I worry about this before buying? After buying it I would removed the soil to make sure the bricks are not exposed to moisture from the soil.

A: Good solution. 1-2 inches of coving is not desirable but is not a fatal flaw either. Usually adobe mud can be packed into the coving once any loose particles are removed and the wall will be as good as new or nearly so.

Q: The windows and door frames are made of steel with the steel extending into the brick in locations such as at the top of the window. If I wanted to replace the single pane windows would I have to mess with the brick? The steel is showing some rust, will these have to be replaced? With removal and replacement of bricks? Is this impossible or just super-expensive?

A: You might check with a local, experienced glass company or window company. Some window manufacturers such as Crestline and Anderson make replacement windows that fit into existing openings. Sometimes the glazing can be removed and replaced with double glazing or a well fit storm window can do the job. Alternatively, with steel windows the glazing can be removed and then the steel frame cut with a reciprocal saw in a couple of places to collapse the framing inward - hourglass style - and the fins can be withdrawn from the masonry. ..... Unless the Weir Brothers went the extra step and anchored the fins into the bricks in some way. They may have nailed or screwed the fins into wood lintels or used some other technique in concrete lintels.

Q: We want to attach a 16 X 20' carport to our adobe home built in 1938 in Tortugas, NM. What is the most secure way to attach the ledger plate?

A: I would bolt through the ledger and wall with 1/2" all thread. Inside the house you can make 4" x 4" plywood washers of 3/4" ply. A large washer on that and then the nut. All of that can be chiseled into the wall and plastered over on the inside. A bolt about every six feet would be about right. I would also consider a 4 x 4 post on a concrete pad under the ledger about every twelve feet to transfer some of the load to the ground.

Q: I recently purchased an adobe home in

San Diego and want to attach a patio cover over part of the south facing exterior wall. How would it be best to attach a ledger to the side of the house? The walls are 12" thick adobe.

A: The best way is to support the ledger with vertical columns at 8- to 10-feet on center on spot foundations four- to six-inches above ground level. The ledger is then best anchored to the wall every four feet or less with 1/2" all-thread bolts through the wall backed up on the interior with 4-inch square or larger plates of 1/4" steel or 3/4" plywood with steel washers in chiseled pockets that allow for the plates, washers, nuts to be plastered over with mud or whatever matches the interior plaster. Should the interior wall be exposed adobes, then use mud troweled and tooled to match the brick pattern. The columns can be omitted but I always used them to lessen various loads on the adobe wall. Should the ledger be located in a position where it is not feasible to drill through and attach inside the wall, then your creative solution will be as good if not better than mine.

Q: I have a 15'X4' wall covered in stucco. It is starting to tilt, so far about 3-5 degrees. I just found out it is adobe underneath. Is there any way to retain this so as to not tear it down?

A: The usual fix is to add a buttress or two on the side toward which the wall is tilting. I have done just that on my own adobe wall.

Q: My parents home is 100+ years old. Some of the interior walls are adode. The wall above a door way has a crack, on either side, that seems to continue to separate. Is there a reasonable method of repairing or reinforcing this situation? Not sure how long this has been apparent. I am concerned of the structural integrity of this wall, but mostly for my family that will continue to live in the house.

A: Cracks on both sides of a door lead to the thought that there might not be a lintel over the door. A proper lintel would be 6" by 10" wood or concrete or stone and it should extend 12" or better yet, 18" on either side of the door to distribute the weight of the wall above the door onto the adobe bricks on both sides. That is the modern code version of a lintel. In historic houses it is often less but works fine over time anyway.

It is not easy, but a lintel can be added after the fact by chiseling half way into the wall and installing half a lintel with shims of wood and/or dirt to support the adobes above and transfer the weight to the adobe walls at the sides. Then, around to the other side of the door and chisel out the other half lintel space to line up with the first and then shims again. With the two halves in place, bolt them together with three or four 1/2" all thread rod. It's that easy. It's just hard work but you will be done in 5 hours except for plastering over the wall unless you want the lintel to be exposed as some people do.

Q: I have an Adobe brick house, I would like to know if it is possible to remove the outer brick leaving the inner wall and replacing the outer brick with a concrete block or brick, the home construction is two side by side rows of Adobe block the blocks measure 16 inches long 8 inches wide 4 inches thick, the header is poured concrete where the roof joints attach?

A: You can certainly do that and I would recommend CMU over fired brick. CMU can be core filled with insulation to reduce heat loss or gain through the wall. However, that is a massive amount of work and I am not sure why you would want to do that.

The Adobe brick is falling apart, I do not know what else to do in order to preserve the value of my home, would you have any suggestions?

Okay, that's a situation where I will allow you to replace the adobe with CMU. It might be best to have a skilled professional do the work and it should proceed with short sections of the wall to make sure that you do not have collapse. The CMU's should be gap-toothed to allow sewing in the next section of wall. Or, it might be apparent to the person doing the work that large sections of wall can be removed and replaced without problems. In true double walls such as this, called two widths, it is customary in brick, CMU and adobe masonry to tie the two walls together at several levels of coursework as the walls go up. It might be as simple as turning adobes sideways to bridge across the two widths or it might be steel strap ties, or rebar butterflies or Durowall, the ladder-like 10-gauge wire that is made for reinforcement in CMU walls.

Alternatively, if the walls are not plastered on the exterior, you might consider patching the adobe where you can - it can be as easy as pulling out deteriorated chunks and replacing them with stiff adobe mud and then once dry, putting standard three coat, cement based stucco on over stucco wire lath. Do not use Western One Coat or any system (Drivit, Sto) with an elastomeric final coat as those products have nearly zero moisture vapor permeability and will hold moisture in the adobe wall. Also, do not use roofing felt, Jumbo Tex or any other vapor barrier material under the wire. That is standard practice in frame houses and is specified by most building codes but should be avoided in masonry houses.

Q:  I have a close friend who lives in Orekhov Ukraine. She has a 60 year old home, constructed of brick with 10 inch adobe walls for the interior. It utilizes a gas heater box with a central heating wall. The electrical and water service are added years after initial construction. To be blunt the house is a mess, to little electrical supply, water pipes freeze in the winter, walls interior and exterior are all cracked and not straight. I would like to gut this house, leaving the brick frame intact, then frame interior with wood and add proper heating, electrical and water services. Can I remove the interior walls without causing structural damage?

A: You can easily remove the interior walls as long as they are not holding anything up. If they are holding something up, just be ready and nimble to quickly put the new structural wood frame interior walls into their place. I am guessing that the climate in the winter is moderately cold, with high humidity, often overcast and not a lot of sunlight. Let's say something like Toronto. I hope you are thinking about abundant insulation for the exterior walls and the roof. Insulation and tight windows and doors will give the most improvement in the thermal performance and the feeling of comfort for the time and expense invested.

Q: How might you attach a interior adobe wall to a exterior straw bale wall. My ideas: rebar pins at 2ft intervals embedded in mortar joint, partial concrete bond beam w/rebar poured in a carved out channel in straw bale wall?

A: The bond beam is a viable method. Rebar does not get much of a grip on adobe. I would consider CMU ladder reinforcement commonly known as DuroWall at least three feet into the adobe wall and five into the straw two-foot intervals. It is bendable so if courses are not perfectly even it can be bent to accommodate. If the straw wall is already up, that won't work so back to the rebar and prayer.

Q: My husband and I purchased a two story Pre-1880 adobe home in Trinidad, CO. Extensive repairs are needed throughout the home to include new roof, plumbing, windows, heating - you name it and we had planned on repairing or replacing it. The adobe is in good shape and the structure appeared very solid and sturdy although we couldn't see exactly what we were dealing with until we continued to remove obstacles. . The more we took out, the more we had to put in the landfill because of the years of neglect. The house has been stripped down to the adobe and wood studs. The floors were uneven and we found this to be caused by years of wear where the 2nd story floor beams were attached straight into the adobe and had loosened. Our contractor has contacted eight structural engineer companies located nearby in Pueblo to address the problem and only one will consider looking at the home because they say that there is too much liability connected with a two story adobe house. The concern is that the structure cannot bear the weight of the roof and large snowfalls which will cause the exterior adobe walls to fall outward and the house to collapse because there is nothing securing the walls. We are waiting to hear back from the one structural engineer that has experience with these types of homes. The home is listed on the historical registry of contributing properties but is not eligible for grants. At some point we are going to have cut our losses and it currently appears that the house will have to be demolished if we cannot find a way to make it 100% safe. Have you heard of problems of this nature and can you recommend any way to proceed?

A: Too bad the engineers of Pueblo cannot access basic published strength of materials numbers for adobe. Adobe walls are one of the most powerful load bearing systems that can be used in home construction. Two-story construction is and has always been permitted by the New Mexico Earthen Building Code. Adobe now has its own page or two in the International Residential Code but that may allow only single-story construction.

Most adobe bricks, old or new, have a compressive strength of 300psi. Taking five-percent of that and if the coursework is halfway decent the top of the wall can bear close to fifteen-hundred pounds per linear foot. That's using a working load of 30 pounds per square inch  on a ten-inch wide wall by twelve-inches. I don't know of any other building system that comes close to that. It's the power of monolithic.

Adobe bricks are expected to have a minimum modulus of rupture of 50psi. That is low for any material but the whole purpose of masonry wall construction is to avoid subjecting materials to flexure which is what MOR measures. Adobe bricks are required to be fully bedded in mortar so that they are not suspended over air space whatsoever as in the case of the MOR test: https://en.wikipedia.org/wiki/Flexural_strength

New Mexico two-story code-compliant construction calls for a 14-inch wall on the first story and a 10-inch wall on the second. If the wall thickness does not step back for the second story then the thickness should be 20-inches for both stories. An old house in Trinidad likely used sixteen-inch-thick walls for both stories. Since Biblical times it has been known by masons that adobe walls are very sturdy if the height is limited to ten-times the width of the wall. Houses with interior adobe walls interlocked with the exterior walls gain further strength from that. Just like a beehive.

And then, 135 years standing is proof far beyond any calculations or laboratory tests that your house will not fail structurally. I would expect that there would have been a few heavy snow storms during that time. On the other hand, 100% safe is a difficult standard for any type of home construction. You might have to settle for 99.973%.

The second story floor beams would hopefully rest on a bond beam that went all around the structure. This was almost always wood in the 1800's and early 1900's and that is fine and meets the modern code. Otherwise there should at least be a wood plate under each beam or better yet a plate that extends under all the beams to spread the load. If none is present a 2 x 4 or 2 x 6 can be situated in a channel cut under the beams and then shimmed with wood and adobe mud to transfer the load from the beams to the plate to the adobe. Then the process can be repeated on the opposite side of the wall so the total plate is 2 x 8 or 2 x 12. Also, it is hoped that there is a bond beam under the roof structure to spread the load and tie the building together at the top. If it is missing, it can be added as described for the floor system above.

Incidentally New Mexico has the Existing Historic Earthen Building Materials Code. The name may change a bit as a result of submissions to the Construction Industries Commission the 5th of this month. Essentially it accepts existing materials and allows repairs and additions to be built in the same manner as the original construction.

Q: Our 1896 2 story Adobe farm house near Carrizozo NM is one room wide with 3 rooms in a row, one after another, on each floor. Rooms are 16 feet wide between load-bearing walls. Adobe walls are 18" thick and rest on dry stacked sandstone . The second floors are very very bouncy. The floors are wide butt-joined pine boards, lacking subfloors, nailed directly to true 2" x 6" ceiling joists. Joists are 16+' long, average 16" between them, with wood cross-braces. Joist ends are embedded in the load bearing walls over a 1"x wood plate but typically there are small mud-filled gaps between joist end bottoms and plate. I do not know how far the joist ends extend into the walls. My plan is to insert one 6" x 6" x 14+' wood beam (girder) into the tops of the non-load bearing adobe cross walls, just below and perpendicular to the bottom of the ceiling joists, in each first floor room. The girder ends will extend 18" through the walls, resting on short horizontal boards (plates). Then I will fasten the bottom of the joists to the girder and install a subfloor. This will cut the joist spans and add support. Does this sound OK? Will the 18" thick non-load bearing adobe walls bear the weight of the girder and the joists and floor on top of it? Or do I need to add columns to help bear the weight of the girder etc?

A: Adobe walls can certainly hold up to the 6 x 6 x 14' if there is a 4" or thicker plate below them to spread the load on the wall - minimum 3' length. Better yet, a full, retrofit bond beam. 2 x 6 @ 16" on center even if true 2" x 6" from the 1896 era are undersized for a 16' span You could also beef them up by placing a 1 x 10 on each side of the 2 x 6's with a cap across their bottom sides to conceal the 2 x 6. This type of sistering is actually fairly common in old structures especially those where the upper floor was not originally expected to have much occupancy. This might or might not be easier than your girder idea, but it would preserve some headroom below.

Q: My grandparents built their home in the 1940s out of Adobe room by room. My mom was small and she remembers them first living in the front room and everyday my grandparents making adobes outside and building on to the house until it became the 1800 sq ft home it is now. The last 300 were added on later with brick for a laundry room and other modern amenities. In fact the entire little community including the church was made from Adobe originally. My mother inherited the house from her parents. Unfortunately the coping has given way on the lower half of the house, the adobes have swollen and the sand is exposed. What steps would you recommend we take to patch up the walls in our Old Adobe home that will prevent future structural damage or further weakening to the Adobe bricks?

A: I am sorry to hear of the troubles you are having with your house but I am glad to know that you want to preserve it. I use the word coping to refer to the top of a wall or parapet. Perhaps you might be referring to the plaster on the lower half of the house. Also, if adobes swell it usually mean that they have been made with an expansive clay such as bentonite that swells when it gets wet. There is bentonite around Fort Worth but I have not heard of it around El Paso. Therefore, I am not sure why your adobes would swell. Sand is actually the most basic and largest part of adobe. In the best bricks it is about %70 and clay is about 30%. Adobe bricks, mortar, plaster and floors can be made with higher content of clay but then the mixture will crack as it dries out. Finely chopped straw stops cracking in the higher clay bricks. When you say that the sand is exposed I am again not quite sure what you are seeing.

What you are talking about seems to me to be a problem of rising damp which is moisture that comes up through concrete foundations and migrates upward through the adobe walls. That is a common problem in the Rio Grande River Valley area and often salt crystals are deposited on the surface of the adobe as the water evaporates and leaves behind the chemicals it has picked up as it rises. This manifests as white crystals on the surface of the walls and is called efflorescence. It is a problem for all types of masonry walls and not just adobe. The solution is usually to plaster with a material that breathes. That is a material with moisture vapor permeability such as just plain mud plaster, lime plaster or even what you might hear only from me is modern cement/lime/sand plaster directly on the adobe with no paper, plastic, tar or any other material that would retard the migration of water out of the wall. There will still be efflorescence but the wall will be dry whichever covering you might choose. Most preservationists do not agree with me at all about the standard stucco but I maintain that we can find values of 5- to 6-perms for the material in trade literature and that is not zero.

A man who bought one of the adobe homes in the area fixed his around 10 years ago. After chatting with him, he said that his key to success was mesh metal netting and concrete. Another gentleman also recommended the mesh metal netting and lime plaster. He used the method to restore some homes and a garage.

The inside wall is classical rising damp. It looks to me as if the interior plaster has a coat of tan paint. If it is a gloss paint, it is much more impermeable than flat or satin paint. Flat paints are always better for interior walls in adobe homes. For the time being I would suggest removing plaster and paint from around that corner up to and a few inches beyond where it has darkened from moisture. That will allow the wall to dry out. It may take several months. I was just in a house with worse problems in Santa Cruz, NM next to Española and the woman who owns it had fans going to accelerate the drying. If plaster is removed to a fairly straight line revealing the adobe bricks and mortar, it will be interpreted as a "truth wall" and not so much as failure of the plaster or an eyesore or worst of all, poor housekeeping.  Once the wall dries, the area can be replastered with gypsum based plaster such as USG Red Top or Structolite. A handy person can also replace the removed plaster with just plain mud plaster which could take a light coat of flat paint of the right color. Better yet, colored clay plaster such as is produced by American Clay in Albuquerque www.americanclay.com or New Mexico Clay  https://nmclay.com/aliz or best of all, hand mixed aliz plaster made from the right colored dirt found in your area. People who do this have their lives changed: as they drive along, they are always looking at cuts in the hills along the highway to spot dirt of a special color.

Outside the wall is just as it should be for the time being. With the plaster gone, the wall can dry. Part of the problem may be attributed to the low curb of concrete which appears to be against the adobe but not under it as would be the case if it were part of the foundation. Also, the concrete skirting (sidewalk?) around the building may be contributing to the problem. Both the curb and skirting slow the ability of the soil around the building to transpire ground moisture upward and evaporate it in addition to concentrating rain water. The curb and skirt appear to have been well done. Many times the curb begins to lean out and any rain that comes in horizontally is funneled against the wall by the curb. Skirting sometimes moves over time and ends up with its slope inward toward the wall and acts as another multiplier of moisture against the wall. These are just the things the Mexicans have seen time and again particularly where a building is right up against a paved street as is more often the custom in Mexico.

The building will certainly collapse in eighty or so years. That gives you some time to deal with the problem. Adobe is slow at anything is does so that works in your favor. For the time being take no action beyond considering removing another foot or so upwards of the exterior plaster. In your climate, exposed adobe walls will loose about 1" of thickness every thirty years from rain and wind. Other good news is that I don't see any coving which is where adobe begins to fall out of the wall at the bottom a little bit at a time due to rain, rain splashing, freeze/thaw cycles. Freeze/thaw is minimal at your location. It is a monster here up north in the snow country.

Cornerstones Community Partnerships in Santa Fe, www.cstones.org, has a nice restoration handbook that covers most of this. They are far more vigorous than I am in the campaign to eliminate cement based plasters on exterior walls. However we agree that you should hold off on the use of any poured concrete.

Q:  I work for an NGO in Mexico building houses for poor families. We plan to start using adobe for our next house (no. 108) and I am trying to figure the best way to attach wooden door and window frames in the adobe openings. Can you help? casitalinda.org

A: Bucks. Door and window bucks are the standard method of installing windows and doors in masonry walls. A buck is a wood frame that outlines the opening and has inside measurements that conform to the window or door to be used or better yet, the buck is a rough buck and the interior dimensions are such that a door or window can be obtained with a trim jamb that - once the wall is finished and the roof is in place - is inserted into the opening with nails/screws and shims just as would be done with the rough opening in a frame house. A buck - rough or finish - can be done with a 50mm x 100mm or 50mm x 150mm framing lumber or the 2 x 4 or 2 x 6 USA equivalents. This facilitates rounded corners - bullnose plaster around openings. Or the builders or owners might prefer wood that is equal to the width of the wall.

With rough bucks built so that the inside dimensions are equal to what a manufacturer would call out for the rough opening in a frame wall, installation of pre-hung doors and windows sash built into trim jambs the hanging process goes quickly and allows builders to use readily available pre-hung doors and fully manufactured windows.

My assumption is that the rough buck is built, stood up, squared and plumbed before the adobes go up so that it becomes integral with the wall. Window bucks are four-sided open boxes. Door bucks are three-sided but for convenience of handling with a bottom piece built with an eye towards removing it once the walls are up. As the coursework goes up, wood to masonry connections can be made every several courses using long nails or screws (150mm or longer) into the back of the buck such that the nails/screws are in mortar joints. Expanded metal lath laid in the mortar for 400mm or more can be bent up and nailed/screwed to the back of the bucks. Heavier metal pieces known as hurricane straps in the USA also work fine.

Most builders in New Mexico use gringo blocks which are no more than a wood frame of 50 x 100mm lumber made with the outside dimensions equal to an adobe brick. The gringo blocks are laid into the coursework to replace full adobe bricks at the back of rough bucks every four or so courses as the walls go up. The rough buck is then screwed/nailed to the rough bucks with fasteners long enough to go through the rough bucks into the gringos. The gringo blocks are filled with mortar mud before the next course goes up.

Over the rough bucks or trim bucks there needs to be a lintel. Wood, concrete, steel, stone. Don't let framers call them headers. This is masonry. Lintels should be the width of the wall or at least 250mm with a minimum depth of 150mm. (100mm depth in a pinch and where openings are no more than a meter.) Lintels should be long enough to have a minimum bearing of 300mm on the masonry on each side of the opening. The best laid lintels have an air gap of around 20mm between their bottom surfaces and the top surfaces of the rough buck. This allows for settling of the adobe mortar without the weight of the masonry above coming down onto the rough buck, or worse, the trim jamb.

Just suppose walls are already going up and there are no bucks in place. It is no real problem but it takes longer to affix trim jambs to adobe walls. I am sure that there are Mexican equivalent to the problem solvers. Number one is deck screws or gold sheetrock screws in a 150mm or longer length. A battery powered drill/driver will send them right through an undersized pilot hole in the wood into the middle of adobe bricks. Anyone who doubts this will be convinced when experiencing the process shows that the drill is barely able to do the job and is as heavily burdened as if the screw were going into wood. Texas Tacks also work. These are 60d nails which are 300mm long. These work will but will require an undersized pilot hole in the adobe which requires a long, thin masonry bit. Original Gorilla Glue works as do the foam in a can insulation/adhesive such as Dow's Great Stuff. These urethanes stick to everything: adobe, wood, kids.

So, back to the beginning. High Speed Adobe Construction begins with speed leads. These are story poles - one at each corner of the building. Plumbed and braced in place they outline the building with the mason’s strings that are run between them to guide the coursework. Tops of courses can be marked with pencil beforehand to eliminate measuring after each course. With speed leads no master mason is needed. Courses should progress up with one course at a time being completed before the string is moved up to start the next course. No level is needed to keep openings plumb because the aforementioned rough bucks are in place and volunteers, owners, kids need only to bring the bricks in a course right up to the back of the bucks.

In your climate progress will be limited to 5 to 7 courses per day. Beyond that the walls will get a wobbly because the mortar has not had time to dry. Humid weather will cut daily production back also. Walls are capped with a continuous bond beam. Both concrete and wood are permitted in the USA adobe codes. A wood bond beam made up of several layers of 50mm thick by 250mm wide lumber will go up in two hours with a crew on the ground cutting and a crew on the wall nailing. A concrete bond beam will take longer but Mexicans are virtuosos of concrete construction. The wood bond beam readily accepts nailing, screwing or strapping to attach the ceiling/roof structural members.

Someone in SMdeQ must have a copy of P.G. McHenry's book, Adobe, Build It Yourself from the University of Arizona Press. About $25USD on Amazon. It covers everything and has great illustrations. Written around 1974 it is still current and has not been surpassed.

Q: We have a house built in the 50s and its exterior is made of adobe. In the back we have a small laundryroom that also has a door leading to the backyard. We are planning on knocking down the exterior wall and extending the laundry room 5ft out and also creating another bedroom. Our concern is, is that the wall we plan on taking down is adobe wall and were afraid that if we take it down it will cause structural damage to the other two walls. Is it possible do to this without causing structural damage to the other two existing walls?

A: If the wall you want to take down supports vigas or beams or joists then it is more difficult. You then have to make provision to support the roof/ceiling support members with a large beam supported by posts that rest on a solid foundation. It the wall is not supporting the roof/ceiling then the job is much easier. You might have to add a buttress or pilaster to keep the remaining wall from wobbling.

Q: I cannot find the answer to the use of castillos (masonry star fort) to strengthen an adobe house.  These are vertical (from floor to ceiling) poured concrete about 8in X 8in.  Do you recommend using this or just steel rods without concrete? I guess my question is what do you recommend to use in the adobe walls to make it earthquake resistant? 

A: I am not familiar with castillos as you use the word. Mexicans and Californians use vertical posts of concrete reinforced with vertical rebar and often tied into the adobe wall with horizontal rebar. Rebar alone in adobe walls is of little structural value since adobe does not grip the rebar tightly as does concrete. In New Mexico, we are fairly casual about earthquake resistance and do nothing or occasionally place Durowall - the ladder shaped 10-Gauge reinforcing used in brick walls - horizontally about every second to fourth course of adobe bricks.  Our quakes are minor here. In places like Chile, Peru, and California greater measures are in order. It's really a job for an experienced engineer to design a system that is appropriate for a particular location and the type of motion induced by an earthquake. The world’s center of anti-seismic knowledge is the Engineering Department of the Catholic Pontifical University in Lima Peru. There are many qualified engineers around the world. If I know where you are located, I can be more specific.

Yes, the 'castillos'  are the vertical  posts of concrete used often in Mexico.  I am building in Baja about 3hrs south of Ensenada. I have decided to go with what my builder is recommending for the shorter part of the project.  But for the portion that will be two story I am going to do the vertical concrete with the half-adobes missing to make the concrete tie in better with the adobe plus horizontal rebar.

A: Before my adobe constructor arrived, I worked on the foundation and also have vertical steel rods (called castillos in Mexico) - four at a time to be filled with cement.  I am now worried that instead of strengthening the walls and making the whole structure more solid, it may actually do the opposite?? because my adobe guy is telling me that he has to make like a groove so the adobes fit a little bit inside the cement because the adobe will not adhere to the cement.  He would prefer to remove 3 rods and leave 1 to place the adobes with a hole that would go there and use that as the wall strengthener. What do you think?  Would you use cement vertical pillars for an adobe construction?  If not what would you use? The adobe house I grew up in has cracks from the earthquakes throughout about 100 years.  It is in pretty good shape but I wanted to make this one with stronger walls.

A: Your adobe person might be right. The concrete pillars are an interruption of the continuity of the adobe walls. On the other hand, adobe is so good at sticking to things, mud mortar and cement based mortar will stick to concrete as well as mud and cement mortars stick to adobe bricks. If the adobes go in first, just leave out half bricks when they occur next to the concrete pillars and when you pour the concrete it will flow into the walls with a little extra formwork. On the other hand Californians and others sometimes just build a post-and-beam structure of reinforced concrete first and then infill the spaces with adobe. Worldwide, the current thinking in best practices as I interpret it is to wrap the exterior of the building with steel mesh such as very heavy duty stucco reinforcement or the very heavy orange plastic webs that we see around highway construction zones for traffic control and safety. Then, one stuccos over and through the mesh. The concept is to produce a building that gives the occupants a few more seconds to get out of the building in a catastrophic event. The building itself might not be suitable for habitation afterwards. Sort of the technique that Volvo pioneered where the car is totalled in a crash but the occupants survive.

Q: We own an adobe home in the historic section of Tucson, AZ. Years after it was origionaly built they added a wooden framed addition to the back of house to add a bathroom and kitchen. This old wooden framed addition is badly damaged by termites. Our plan is to demolish the wooden addition and rebuild the addition in adobe. Our question is how to best attach the new adobes to old adobes? The foundation on the old house is primitive. Large rocks mixed in cement. Our "new" foundation for the additon will have to be built to modern code. So it's going to end up being on basicly two separate foundations. I am worried that where the old adobes meet the new adobes will forever have separation and cracking issues over time. Any suggestions on how attach the new work to the old to help stop this from happening?

A: Have a glass of wine or two and proceed. Nothing can stop masonry walls from small separation cracks where two separate structures join. That's why the masonry industry has developed expansion joints of various types. If you are going to stucco the finished product you might consider a metal expansion joint. I don't care for the looks of them so I just stucco over the two sections and keep some butyl caulk handy five years later when cracks appear. Sometimes they do not appear. You may have a really good foundation on the original building even if it does not meet current code. After all, it has had over a century to settle into its final shape. But then you might have cracks as the new, code-approved foundation settles a bit or the mortar joints in the new wall shrink a millimeter per course. Some people pull half bricks out of the old wall and sew new bricks into the pockets as the new wall goes up. That's the best method but it will still crack. Other people drill six- to 12-inches into the existing wall and insert a 1/2- or 3/4-inch rebar and bury two- or more-feet of it in the mortar joints of the new wall. But it will still crack. Reward yourself with another glass of wine. A hundred years from now observers of the two parts of the home will pronounce you a genius cracks or no cracks. 

Q: You answered a question about the circular arch window. You said that the arch needed a few feet of solid wall above the arch. In my situation, I have a 40cm thick adobe wall, and will place a 20cm concrete bond beam on top of the wall. How do you feel your recommendation of "a few feet of solid wall above" applies to my structure? In other words, how much solid wall above the arch is sufficient in my case?

A: With that concrete bond beam above the arch it will act as a lintel over the arch and will take up the load of the structure above. Therefore there would not be a need for any adobe above the arch. It would not hurt to thicken the concrete to the appropriate depth that would be needed if there were no arch.

Q: Is it possible to use metal vigas for an adobe structure? And if so, what could we use and what size would they need to be?

A: Metal vigas have been used in several adobe houses. Pancho Villa is said to have built a house that used car chassis for vigas. Steel bar trusses were used in an adobe house in Albuquerque to save money,They seem to be using trusses of rectangular tubing, nicely fabricated. Five by eight steel tubing would serve nicely as vigas in a flat or slightly sloped roof. Size really depends on the span between the walls and the spacing of the trusses. Don't do this without engineering from a steel fabricator or an engineer. Just arrange to have plates with holes drilled in order to bolt, spike or lag the trusses to the bond beam of the structure. This is not stuff that you will find at Home Depot.

Q I: presently have 5' high x 2' wide windows facing south. Is it OK to add further framing and reduce size of windows to say three sections? Also 5 years ago had a new roof which was a heavier gauge than old one; now I am seeing more cracks near roof.

A: Windows can - almost always -  be reduced in size by a competent carpenter or builder. Making windows bigger is often not easy. Metal roofs are popular because they are light. Even heavier gauge metal should not add enough weight to your roof system to cause problems. The cracks may be coming from another source.

Q: My husband and I are considering the purchase of a home in Carmel that is constructed in what we are told is the “Post-Adobe” style. The walls are made primarily of adobe bricks and held up by large timbers. The electrical is run through the timber’s and the roof is supported by rough hewn lumber. The building was originally constructed in 1948 and has had a few additions done to it over the years, nothing recent and all of which appear to also be done in a similar style.. If we remove an adobe section of wall, does the house framing remain structurally in tact?

A: If the structure is true post and beam with adobe infill then the wood bearing elements could be expected to hold the structure up if an adobe wall below is removed. However, over time there may have been some settling that would have transferred some or all of the weight of the structure above the beams down onto the adobe. I have done two small post and beam with adobe infill projects on my own home. I would be cautious about removing any adobe without closely watching/monitoring the wood elements to see if they move downwards. On one project the opposite took place and the adobe walls shrank downwards as the adobe mortar dried so there was a 3/8" gap between the wood beam and the adobe below. You can remove parts of the adobe wall and expect the wood beam above to bridge over the opening up to five feet. If the beam is sound, it will act like a lintel. Mainly, this all depends on the person who is doing it remaining vigilant to see if there is any movement of wood or adobe above the opening.

Q: I'm looking for some info on having an attached solarium/greenhouse to an adobe home. This will be a new structure in Tularosa ... using 4x10x14 bricks (14" width) ... that is, about 84" of adobe wall, +6" stem wall and 6" bond beam ... 96" wall.  A New Mexico Style Pitched metal roof adobe dwelling ... with the plank and beam ceiling. My question ... Greenhouses are notorious for humidity ... so I was pondering doing a veneer of dry stone on the 42' wall where the sunken greenhouse would be attached ... do you think this would mitigate the moisture into the adobe?

A: My experience with adobe walls in an attached greenhouse is that there is no problem with moisture. My experience goes back to the Sundwellings Demonstration Center at Ghost Ranch in 1976/7. Also my own home which has become very minimal in the plant inventory due to reasons other than humidity/moisture. Some study in the Pacific Northwest showed that adobe bricks are strongest - by a little bit - at 60% humidity. If the stone veneer is a moisture vapor barrier, then if moisture gets behind it, the bond between adobe and stone can be broken and the stone falls off.

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