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How to Build Underground
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Paul Shippee is director of Colorado Sunworks and is a solar designer and builder. He was the founding President of the Colorado Solar Energy Association, and a teacher. Paul holds a degree in Civil Engineering, with a major in Structural Engineering from the University of Connecticut. He helped plan housing experiments in energy conservation with the U.S. Department of Housing and Urban Development, and designed and built the SunEarth House, which was the best-rated energy conservation, earth-sheltered home in a HUD-sponsored study. He holds a U.S. patent on a solar water heating system. Paul is currently living in a rammed-earth/strawbale home that he has designed as a personal residence in Colorado. His book, THE LANGUAGE OF SOLAR ENERGY: Heat Loss & Solar Gain for Buildings, is available from his website: crestonesolarschool.com.

Reinforced Concrete

Q: I am a student of final year architecture and working on "under ground commercial spaces" as my thesis project but not getting relevant information regarding this. My aim is to emphasize building materials and construction technology and also the important services required. If you could enlighten my way, I will be heartily thankful to you.

A: (John MacMillian) The basic construction technique is to build forms, place rebar into the forms, then pour concrete into the forms. After the concrete cures the forms can be removed. Any plumbing or electrical service must be in place (and tested) before the concrete is poured into the forms. In general, for a one story building, the walls would be at least 12 inches thick. As an alternative, concrete blocks are often used. The block wall is built (with rebar and all services in place). Then the blocks are filled with concrete. Using this technique, no form is required. A similar method uses large, hollow, styrofoam blocks instead of the concrete blocks. This adds two inches of insulation to the interior and exterior of the building.

Q: If I built an earth-covered house what are the choices for the roof construction? Would it be pre-stressed concrete or what?

A: For an earth covered house the roof loads are great, even for one foot of earth cover. One foot of earth is equal to a two foot deep pond of water on the roof, or 10-20 feet of snow. So the safety factor is important. You can use pre-stressed concrete panels or steel bar joists with a 2 inch concrete decking poured over that. All must be engineered carefully for structural safety.

Q: If you live in an earthquake prone area, how can you design the earth sheltered home to be earthquake proof? How does it become earthquake proof.

A: You have to hire a structural engineer who is trained in earthquake reinforcement to design the support elements. This is essential.

Q: I would like to eventually build an underground house on land that consists of 40 ft of sand (according to our well supplier). Generally the rainfall is about 35-45 inches a year, but water drains away immediately. Will this soil structure support an underground dwelling? Also, what material would be best suited for the task?

A: Sand will not support anything, but that's not the issue. It is good that you have sand. It's a good insulator when dry. When building underground, or earth-sheltered, use concrete. Can't be beat for its structural strength and longevity either underground or underwater. You will need these features to support earth mass overhead and to hold up the walls. Find a good structural engineer in your area and ask him what he would do, after you sketch up what you want to do. Google Sketchup, in fact, to find a design software that you might be able to learn, like, and use. It's free!

Q: I am trying to build an underground (or partially underground 4' to 6' below ground) cabin in central Texas. The soil is very fine Padina sand. This sand goes very deep and does not hold water. The water table is 30' to 40' feet. I am thinking of mixing this sand and Portland cement (approx. ratio 6:1) with little or no larger rock. Is it possible to put a mixture dry in the forms and mist water on the top of the forms? (the forms are 20' long by 1' high); pour 1 layer, let it cure, stack another on top, pour, cure, etc. Should I add any retarder to this mix?

A: I don't think misting the cement/sand mix will be a good idea for an underground structure that must withstand earth loads. Fine sand and cement can make a strong mix concrete, but I would make some test cylinders and have them tested at a reliable lab. Make the cylinders according to their specs, and test your desired ratios of sand/cement for ultimate strength. This is the usual and safe procedure.

Q: I live in Honolulu, where humidity is usually pretty high and temperatures generally between 70 - 85F. Beneath some steep hillside property, I'm considering a large cut-and-cover earth-sheltered workspace/garage/occasional living-space. The appeal of earth-sheltering would be both to keep the space cool, as well as to minimize noise-annoyances from my oddball projects (say, running a big router or grinding steel). I've only just started reading what I can find online, and have to filter out a lot of irrelevant info. One such issue: in the Honolulu climate, would you expect that uninsulated, plain concrete surfaces within the shelter would condense moisture to the point where it would cause a problem?

A: (Kelly)  I don't have any direct experience building in this sort of climate, but one resource that you might read is shapingbuildings1.pdf , where the author states: "Earth walls don't get hot or cool very quickly because earth insulates better than concrete. Heavy concrete walls in very humid areas become frequently damp from condensation, causing algae or mold growth. Solid earth walls will receive less condensation than concrete because they are less dense, and because they absorb more humidity." For this reason you might consider building the walls with earthbags filled with earthen material rather than with concrete. You might check my other website, www.earthbagbuilding.com, for more information about earthbag building in general.

Q: I'm looking to build a completely underground space with 12' of over burden. My very limited experience is that a vault is the best load bearing shape. My plan is to cut and cover, using a prefab steel arch building as a form, braced on the inside with plenty of lumber. Rebar and mesh on top of the arch and then concrete over the whole thing. My question- will the steel arch building make a suitable form? Will the arch building, along with the bracing, support the concrete and rebar while it dries?

A: Yes, the steel arch building can make a suitable form. Questions of ‘structural support’ can only be answered by rigorous analysis and calculations. I suggest... no, strongly advise...that a local structural engineer analyze the loads and design adequate structural support. Living under 12’ (feet or inches?) of earth is not a matter of luck, speculation, conjecture, or guessing. Remember, Safety First!!!!

Q: We are a group of harmless, fun loving people dreaming of a perfect utopian habitat. We want to build a community centre in Kissimmee, Florida near Orlando. We're excited to implement passive solar design principles and use natural materials as far as possible with native landscape. The land (7 acres) is entirely flat, sandy soil and has a man made large pond on the east side. I have read and re-read greenhomebuilding and I think earth shelter/berming seems to best suit my objective and I'm also excited about the organic look it allows both inside and outside, a breather from straight lines! I have some questions and I hope I'm not asking too many: 1. The 100 year flood elevation is 66 and we are at 67. Does this mean the earth shelter is unsuitable? even if it is above ground and bermed? 2. Since one of the design objectives is to use natural materials, can I use bamboo for form and to strengthen the roof instead of reinforcement? 3. In continuation to the above question, what material can I use for roofing apart from cement? Is there a natural material option or maybe a energy efficient material/green product that I can couple with bamboo for structural stability? 4. For this climate, what sides should I berm up and what sides should have openings? 5. Is cross ventilation a must to avoid humidity and how can I achieve this in berming up 3 sides? 6. What sort of foundation is required for this type of shelter and the type of soil? 7. Since the water table is high, it will not allow for digging. So where can the earth for berming come from? Isn't it expensive and hence unsustainable to purchase it? 8. Are there any documents available to help me during design/construction, like a guide that I can refer to?

A: You are asking all the righteous questions here before you rush into such a project. I am not familiar with Florida or high water tables so my experience is limited. A basic rule for earth supported overhead is to get a local structural engineer involved in the design. Earth berming and lots of insulation seem essential due to the hot, humid weather. However, since nights are probably not very cool then natural night cooling is not feasible unless you can use the coolness of deep earth or subground water. I would suggest building a smaller model first, like a shed to get some experience with all of your questions. Hands-on learning is best where mistakes can be turned into learning.

Will berming keep the inside cool at night in a hot and humid place? I could have wind scoops connecting to form a respiratory network for air circulation. What do you suggest?

Berming in your climate will not have much effect on cooling needs, because it is so warm there most of the year that
Ground temps are warm maybe down to 6-8 ft Wind (if you have much) scoops might be utilized ---I would dig down 10-20 ft into the earth and see what the soil & water temps are down there. If around 50-60F (or even 70F) then you could use them as a ground source for cooling needs.

Q: I am looking at building an underground house in the future. I would like the entire house to be underground and to be inside of a hill. I would like to only have a door and maybe a window or two showing to the outside. Is it possible under current building codes to build the entire house underground? Also I need to find a suitable building material for my area. I live in Georgia and it is very humid. I have looked into the concrete but it seems to be quite susceptible to humidity issues.

A: Concrete is strong, and you need strong to hold up an earthen structure. You can find ways to deal with the moisture issues. Windows for fire egress are required by building codes from sleeping rooms, and you also need ventilation.

Q: We are building in the mountains of Catron County New Mexico. We would like for three walls to be underground, with the fourth wall above ground with windows and doors -- like a daylight basement without the first floor. The lot is near the continental divide, so it will need to be warm in the winter. Summer temperatures are not extreme. What would be the best natural construction techniques and materials to use in this context?

A: Whatever you use for the walls, they will need to be structurally adequate and insulated. Most underground walls use concrete or masonry blocks…both well reinforced with steel rebar. You have to think of not only earth pressure on walls but also moisture and deterioration of various kinds.

Insulated Concrete Forms

Q: Do you know of anyone doing earth-sheltered homes made with the technology that involves foam blocks and poured concrete? Are plans available?

A: (John MacMillian) I do know someone who built his home using them. It went well and his home is great, well insulated, strong, and very energy efficient. The blocks were easy to use and the walls went up fast! I wish they were available when I built my home!

Q: I am currently designing an earth-sheltered home, but have been unable to determine the best building material for my location and how this will affect my design. I have been leaning toward lightweight concrete lately as I am impressed with the creative flexibility of it. I live in an extreme climate (Northern Canada)temperatures range anywhere from -40 to 104F, the prairies are dry and windy. I will be covering all but the south side of the home with earth, as this is where my greenhouse will be going. I would like to build it right into the house rather than externally and am expecting high humidity inside there, I will be separating the greenhouse from the main house with glass. I was hoping you could recommend the best material for me to work with, or if you know of any reference materials dealing specifically with this climate.

A: (John MacMillian) I would suggest using foam blocks and poured concrete. This method is very easy to use. The foam blocks are shipped flat and put together with plastic spacers. The walls go up quickly and are tied together with string. Additional wood braces are added, and then the walls are filled with concrete. Make sure you fill the wall in layers to help prevent a blowout. (Filling the walls in layers of a couple feet or so at a time allows the concrete to setup and reduces the likelihood of a blowout.) I've seen this technique used a couple of time, always with great success. If it's available in your area, I would suggest you explore using this method.

Q: I would like to build a earth-shelter detached garage in Northern Illinois. The site has enough slope. The 30' x 24' garage with earth roof could be completely 'encased' except for the doors. I like the foam block concept...but wonder if its overkill or, in fact, contrary to my desire to let the garage temperature be mitigated by the soil temp.

A: Well, with no windows on EWN sides the earth cover should be easy. Pay strict attention to the structural design for roof and walls as these support big loads. Of course you will have the 30 ft side facing south with lots of windows??  In this case, two inches of rigid styrofoam (not beadboard) on the outside of of 8-10 inch concrete walls will store the passive solar heat, IF you insulate the south windows on cold nights.

I don't see much advantage for using foam block... In fact it's probably a disadvantage if you want to use passive solar, and an advantage if you only want to heat occasionally with a wood stove or other fuel.

Earthbags

Q: I am wondering is there a way to build an earth shelter with using only natural materials?

A: (Kelly) One possibility for earthsheltering with natural materials is to make small domes, cones, or vaults with earthbags which can be backfilled. These can be stabilized to some extent with poles or vigas of wood. But be careful with putting too much weight on these.

Q: We want to build a 1000 sf home in St Petersburg, FL. This area has a summer rainy season, flat terrain and very sandy soil. the hot season is long, and we do have a cold winter season-2 months. What possibilities are there for such a situation?

A: Being in the ground is a proven way to keep a dwelling cool in a hot tropical climate. Earthbags are an inexpensive way for an owner to build. If you design the walls to be round, they will be able to hold back much more earth than a straight wall.

Q: What other materials are available besides concrete and PSP for a earthshelter?

A: (Kelly) Other methods of building underground walls that I know about are tires (as with earthships) and earthbags. There is also a manufactured product called Aerated Autoclaved Concrete (AAC), that does use some cement, but is much more lightweight and insulating. Earthbags are another possibility.

Q: I live in Honolulu, where humidity is usually pretty high and temperatures generally between 70 - 85F. Beneath some steep hillside property, I'm considering a large cut-and-cover earth-sheltered workspace/garage/occasional living-space. The appeal of earth-sheltering would be both to keep the space cool, as well as to minimize noise-annoyances from my oddball projects (say, running a big router or grinding steel). I've only just started reading what I can find online, and have to filter out a lot of irrelevant info. One such issue: in the Honolulu climate, would you expect that uninsulated, plain concrete surfaces within the shelter would condense moisture to the point where it would cause a problem?

A: (Kelly)  I don't have any direct experience building in this sort of climate, but one resource that you might read is shapingbuildings1.pdf , where the author states: "Earth walls don't get hot or cool very quickly because earth insulates better than concrete. Heavy concrete walls in very humid areas become frequently damp from condensation, causing algae or mold growth. Solid earth walls will receive less condensation than concrete because they are less dense, and because they absorb more humidity." For this reason you might consider building the walls with earthbags filled with earthen material rather than with concrete. You might check my other website, www.earthbagbuilding.com, for more information about earthbag building in general.

Q: How do you suggest I build an underground room in the woods behind my house?

A: There are a lot of ways to go about doing this. One simple way is to bury a large section of steel culvert, either vertically or horizontally depending on size of configuration. You can also employ earthbags filled with the soil on site to create walls, especially if they are curved to resist caving in. A roof is a little more complicated in that you need heavy duty support with steel or wooden beams, reinforced concrete, or such.

Q: We are building in the mountains of Catron County New Mexico. We would like for three walls to be underground, with the fourth wall above ground with windows and doors -- like a daylight basement without the first floor. The lot is near the continental divide, so it will need to be warm in the winter. Summer temperatures are not extreme. What would be the best natural construction techniques and materials to use in this context?

A: (Kelly) It is possible to build an underground or earth-sheltered home using earthbags either filled with soil or crushed volcanic stone (easily found in that area) which is insulating.

Tires

Q: I want to build a retaining wall about 6 to 8' high. I'd like to make a form and stack concrete made blocks. Is this possible? I've also thought of using discarded tires.

A: (Kelly)A retaining wall 6-8 feet high would have a lot of lateral pressure on it. If the wall is curved, with the convex portion against the earth, it will be much stronger. Tires would be more stable than the block wall, but might also be more work, because the tires need to be packed with earth, as they are in an earthship. You might look for a book about earthships to get some ideas for this.

Brick Domes

Q: I need some ideas on how to construct a round roof that's roughly 3 meters in diameter which will need to support 1.5-1 foot of earth plants etc. The original structure is a type of antique cylo (situated close to Barcelona) the walls are stone and a type mortar roughly a foot thick. Only half of the structure is visible due to the ground levels and from this side will be a small opening (with door) down 3 feet into the planned sauna! What would you recommend in the way of material? concrete beams with blocks in between with a layer of cement over the top?

A: (Kelly) I would seriously consider the possibility of making a shallow dome with bricks as is commonly done in Mexico and perhaps Spain. The artisans are able to accomplish this without any formwork, believe it or not.

Wooden Beams and Decking

Q: I am wondering is there a way to build an earth shelter with using only natural materials?

A: Root cellars are often made with natural materials, and they are earth shelter, and they are small. However, for a home with larger rooms it is difficult to hold up an earth covered roof with naturals materials. One here that I know of had wood round roof beams (tree trunks) that were over 2 ft in diameter placed about 4-6 ft on center to hold up two ft of earth roof over a span of about 20 ft. So it can be done, BUT the safety issue of all that weight overhead is something to be afraid of every night!  BE CAREFUL!!!

Post/Shoring/Polyethylene

Q: I am only 14 years old but I am very much interested in underground buildings. I like to build and rebuild stuff. I was thinking about building an underground kind of living space that would not be able to be seen by someone just walking along. I wanted a private area, secluded, isolated. Somewhere I could go to be only and in my own privacy. I have once before built a "room" underground kind of like an underground shelter. I just need help on how to make it waterproof, how to build frames, etc. and be able to this with not much money. (Something I don't have due to age) But I am asking you not to look at me as an immature teenager just dreaming but to actually help me cause I am determined to do this and I very much want to do this. Please help if possible.

A: I think the Indians have built these kind of shelters. Also, the first settlers in Nebraska built them to help get through their first winter there. The biggest danger and safety concern in building underground spaces is that the roof covered with earth is not supported well enough and might fall in on you. So, watch out for that. Find a south facing hill and dig a hole into it. Make the roof out of thick logs placed close together. Keep the water out by placing a few layers of plastic over the top, then put dirt on top of that. Remember, dirt is heavy and water will make it even heavier, so pay much and close attention to the roof structure.

Natural Caves

Q: I would like to know if you have any new info on cave dwellings. I have a south facing cave on my property and would like to chisel into it for a home dwelling without the huge bank loans of earth dwelling contractors of 100 dollars per square foot.

A: Sometimes those things cave in, especially if you start chiseling, so be careful! Also, they can be damp... Try spending the night in there and see how you like it.

Q: I want to dig an arched hole in the side of a mountain and therein build a home. I've searched the terms "earth-sheltered" and "underground homes", and I come up with thousands of hits, mostly related to any structure with grass on it. Could you tell me how to narrow my search to sites related to my "arched hole?" Do you know of any companies who construct such dwellings?

A: (Kelly) The feasibility of digging such an arched hole in your mountain will depend greatly on the geologic reality of the site; if it is stone or well consolidated soil, then it might be just a matter of digging or blasting your way in...if the soil is looser and of a caving formation, then the whole project will be much more delicate and will probably require formwork and engineered support. This is all so specific, you are best off getting advice from an engineer locally.

As for terms to research this via the internet, I might suggest "cave homes" "tunneling" "digging mine shafts" "digging caves" as possibilities. You may need to employ professionals in the mining or tunneling industry to accomplish this.

Dealing with Water

Q: I am a final year architecture student from Mumbai India. My thesis topic is "training center for the blind". I'm trying to use temperature differences above and below the ground as orientation landmarks for the blind which helps them locate where they are within the campus. The site is at the bank of a river. The climate is hot and humid. Also I'm not able to find out the exact water table level. All I know is that river sand is produced in the vicinity. Also the site is primarily an agricultural land and gets flooded during monsoons because a lot of digging has been taking place. Could you please guide me on the feasibility of an earth sheltered structure in my case and also as to what assumptions could I make regarding the water table? What measures should I take to overcome the problem of excessive humidity (around 90% in summers and monsoons)?

A: (John MacMillian) I frankly would not build an earth sheltered home in the area you have described. To me that's just asking for trouble to build in a area with a high water table and frequent flooding.

Digging in or Berming?

Q: This might be a stupid question: I am looking to build an earth shelter home, but the land I own is fairly flat. How can we do the dirt work to make is possible for us to put an earth-sheltered home in?

A: Well, that's easy. The earth sheltered home I built, known as the SunEarth Home, was built on a flat unlikely site. The remedy was to bring dirt in and pile it up around the house walls (EWN, but not on the South side, which is all glass), and -as I did- one foot deep on the roof to make a green roof. If you are planning to excavate for a full basement, then that earth can be saved and used for the earth shelter. It's a win-win all around.

Q: I live in Oklahoma, a place where earth shelters/berming is simply not done. There isn't a single contractor I can find with any experience. However, I am very interested in trying to make a minimal environmental impact and reduce my energy consumption. I have a beautiful sloped wooded acreage that I would like to build a earth sheltered home or bermed home (if I must) on. I had planned several months ago to build a home with a walkout basement, also EXTREMELY rare here. As I did more research, I started wondering if there is a way to make a single walkout basement into an earth sheltered home. Aren't they similar? Do you know how this could be done? I believe our contractor is very intelligent and he thinks outside the box with even doing basements here. It just seems like they are about the same, so could you make the roof hold enough weight to put earth on top, or could you just put a roof on the top and be bermed on three sides?

A: I remember Oklahoma as a place where earth sheltered homes have been built in the recent past. When I built my earth covered house in Colorado in 1978 -the SunEarth House- I put 12 inches of dirt on the roof. It's still there! You can see a picture of it here: http://www.crestonesolarschool.com

It's expensive to hold dirt up on a roof. The challenge would be to figure what the benefit to you would be -what you value about it- and then design a lowest cost structural system to hold it up. This needs to be done by a qualified structural engineer for safety. Some copies built near my SunEarth like the earth berming idea but left the dirt off the roof, replacing it with mucho insulation.

I believe you can build an earthsheltered home anywhere; it's just a matter of learning & accepting the expense. It's not that hard. Concrete (as in walls, which is what I used) is used to hold big loads when designed properly.

There are also water, moisture, and roof drainage issues that need to be addressed in detail before building. What about windows on the east west and north sides that would require openings in the earth shelter. And the south side I presume on your nice hillside would be all or mostly double glass insulated on winter nights. And what about skylight openings in the roof to let light in and avoid a cave-like interior? Many questions to address... Let the sun in and insulate well!

Q: Is it wiser/cheaper to berm than build below grade?

A: (Kelly) I would say this depends more on the nature of your building site. If you have a nice south-facing hillside to dig into, this might be better than berming or digging down. If there are problems with water tables or drainage, then berming might be a better option.

Q: I would like to build an earth friendly home in eastern Texas. The land is mostly river bottom. The main issues include flooding...even though some of the land is above the 100-year flood plain...you really can't dig a basement. Also, it is very rarely cold...but often very hot...and humid. I've seen earth homes in the mountains and the desert...but not the gulf bayous. Any ideas?

A: (Kelly) Even though you might not want to dig into the ground because of the danger of flooding, you can still take advantage of being mostly underground by substantially berming the house and/or earthsheltering with a green roof. These measures will help keep the home cooler when it gets hot outside. Also, the use of thick earthen plaster on the inside will help with the humidity, since it will absorb quite a bit without any problems.

Miscellaneous

Q: I am currently in Afghanistan working as a Security Coordinator. One of my jobs is to have bomb barriers placed around walls, buildings and secure locations. We use a product called Hesco. Basically all this consists of is a stiff wire with about 2 inch squares and resembles chicken wire but heavier and thicker. The wire is cut in 4X4 ft. squares (a box with no top or bottom); sizes vary from 3ft. squares to anything up to 4 ft square by 8 ft. tall. A felt type fabric is stapled inside on all sides to hold sand or dirt inside the box then the square is filled with sand. I have stacked these as high as 10 to 15 feet and have seen numerous bunkers built from these Hesco barriers.

Now for the question. When I stop this madness and go home I want to build an underground or earth sheltered house and employ as much green tech into it as possible. Do you think this same design would work for the walls either using a similar system of square wire or by placing 6"x6" posts every 4' and placing the wire and fabric on the outside of the posts with the standard plastic, blue board insulation drainage and backfill? I think it would be less expensive, less labor intense than tires or earthbags and go up faster. I live in Alabama where we do have a degree of humidity, somewhat mild winters but a lot of tornadoes. I have not heard of anyone using this but can't see why it wouldn't work.

A: Sounds like your idea would work, basically; but many details would have to be considered, from a design point of view, to make the house workable. Houses with various earthen walls have always been built all over the world.

Q: My son is looking at purchasing a bermed home built in the late 80's, but it is too small. Can part of the earth berm be moved to allow a bi-level addition?

A: YES, it can.  Glad you asked! Just be careful not to hit or damage the house wall with the equipment moving the earth away from the house.

Q: I'm curious to know which type of building method would be best for an earthbermed dwelling, especially one which is 3/4 or more in the earth.

A: (Kelly) I would recommend staying with materials that are known to remain solid when exposed to moisture, such as, stone, lightweight concrete, earthbags filled with earth, gravel, or volcanic stone, insulated concrete forms, or shotcrete systems for any earthbermed construction.

Q: I am a graduate architecture student doing an energy efficient kindergarten in Blacksburg,Virginia. What would be the best natural materials? Also I am going for a subterranean structure (site has high slope). Any suggestions on that are welcome.

A: (Kelly) The best materials to use for building underground are those that are naturally resistant to decay under those conditions, so masonry materials like stone, brick, concrete work well. Another possibility is earthbags which can be filled with the local soil (see www.earthbagbuilding.com for possibilities). Tire walls are another possibility. The materials used need to suit the design, and any underground structure requires stringent engineering for safety, especially for the roof if is to be covered with soil.

Q: My question is if the Quad-Lock insulated concrete system would work for an underground home or office buildings arrangement using their roof design? Secondly in Oklahoma?

A: I am not familiar with "Quad-Lock", sorry. I do recommend you get the structural loading specifications from the manufacturer...then do as they say; call them if necessary and talk with their engineer. That's what I would do...

Q: I was thinking about building a basement that is near a garage but not under it. And a sub-basement under that basement. I wish to build it with welded steel. I am an Iron Worker and can obtain lots of steel. I also don't want any of it visible, and I want to dig 20 feet deep. I wonder if you think this will work?

A: (Kelly) You can certainly build an underground structure using steel, especially if you 1) have all of the structure engineered to withstand all potential loads, and 2) deal with mitigating any potential issues with the steel rusting over time. Steel reinforced concrete is the most common method of building underground. One easy way to form up walls that would do well underground is with insulated concrete forms (ICFs)...and then you could use your steel to make the mid-level floor and the roof.

Q: I have searched the net till my eyeballs are falling out trying to find information on earth-berming the concrete block side walls of an existing house. I think I have adequate information on water-proofing & insulating the walls, but do you know of any publications on what kind of reinforcing could be done to in-place walls so they could withstand the lateral stress of the retrofitted earth berm?

A: If I read your question right, the reason you cannot find that info is because it is a structural liability issue, and all local soils are different. I recommend you hire a local structural engineer to analyze and be SAFE!!

Q: I am buying a foreclosed property. It is going to need a new roof in at the most 5 years. I am really thinking about planting my new roof. I don't know anything about it, the green roofs, except I love plants. And I am wanting to remodel the new ( new to us but built in 1953) place as green and energy efficient as possible. Do you have any sources that might tell me how to do a green roof myself and what materials I would need to do it? As well as, can I do it in the desert, will cacti work on the roof or is it something that is better done in a more temperate climate?

A: (Kelly) Green roofs can be very heavy and so often require special attention to the load-bearing capacity of the structure, and this needs to be evaluated in a case-by-case basis. For this reason, you might best be advised to communicate with a local green professional. There are several directories of such professionals listed partway down the home page. As for what might be planted on a green roof, your idea of planting cactus, or other plants that naturally do well in your arid environment is probably the best.

Q: I want to build an underground bunker. I want to make the bunker as deep as possible, but I am lost on structurally what I will need, how thick my wall and ceiling would have to be. If I wanted to make it 50 - 100 ft below the surface, what would I have to do, any advice would be greatly appreciated. My idea was have about 5-10ft thick walls and possibly a 10ft thick roof/ceiling.

A (Kelly): There are some fairly simple ways to build small structures below ground, but going that far down can present some real problems...that is a major excavation and access to it later might be tricky. If you want to be that far below ground, you might seek a cave or old mine that you can exploit, or at least find a hill that you can dig into. Otherwise, I might suggest looking into using a large cement or steel culvert that can be buried with no concern of collapse, or possibly using a heavy-duty steel vault structure, like a quonset that can be buried. For shallower depths, more conventional concepts like those shown at http://dreamgreenhomes.com/styles/earthsheltered/livingroofs.htm are possible. I suggest that you get the professional opinion of an engineer about what can be done.

Q: What do you think of a completely underground home design with a using a tank that is sized 15 ft tall-x-15 ft wide-x-60 ft long as the basic home system? The idea is to completely bury the unit down to the depth of 35 ft with the overhead cover of 15 ft, with a rock bed depth of 5.ft for the tank home; the tank is covered in LineX truck bed liner as a waterproofing set up.

A: Sounds great; like a ground hog! How will you get daylight in there? And fresh air ventilation? And exhaust stacks? What's the tank made of? Steel? Concrete? Wood? I would have a structural engineer do the earth-load calculations, just to make sure it won't collapse. Also examine the structural integrity of the tank...cracks, weak spots, holes you might cut, etc. so examine the structural integrity of the tank...cracks, weak spots, holes you might cut, etc.

The tank is made out of heavy duty steel and it design to be completely buried and the light is from the standard overhead light and the ventilation is from a 12 volt system that bring's air into the tank and moved around inside the tank and exhausted out the air exhaust piping system...The time spent inside one is coming from spending a night in a underground cave home and I found it was one of the best night sleep I got at the time of visit and I thought it was a good idea for a home for a person.

The engineer has approved the design and it will hold the above earth weight. The tank with the sides and bottom and top is covered with pea gravel to help with the drainage around the tank into the soil along with a custom design side French drain around he tank to help with the drainage of the water that come's from the seepage of the ground. The tank is coated with linex bedliner coating for rust and water proofing system.

Sounds good...hope the tank liner is not toxic? I suggest providing light tubes (aka sun tubes) to bring some daylight in a few places, as well as air or you might later wish you had?

Q: We live on a waterfront sloped site which is granite. I would like to expand a few rooms but cannot go forward as I'm not allowed to build any closer to the water, so I have to expand back. This could be done if the lower floors were moved out against the granite rock. Is it possible to do this, to build up against the rock slope?

A: Not sure where you live, but rocks are good conductors of heat and will drain heat from your house out into the air or ground. Otherwise seems to be no problem...unless rising seas begin in your areas due to climate chaos?

Q: My husband and I recently purchased a lake home that has perfect views of the lake from one side, but is too small and outdated from an aesthetic standpoint. The property is long and narrow, and is significantly sloped, so in order to take advantage of the large (long) property and not tear down the current structure, we would like to add on to the current structure, but are wondering if there will be size limitations to how far into the hill we will be able to build and if there are significant cost differences associated with "building up" versus "building in?"

A: (Kelly) With proper engineering you can dig into that hill as far as you want, and there might be some thermal advantages of doing so. But earth-sheltered construction often does cost more because of all the excavation and the cost of reinforced materials to withstand the pressures of the soil. To thoroughly evaluate the associated costs, I suggest conferring with an engineer or architect in your locality.

Q: How do you suggest I build an underground room in the woods behind my house?

A: There are a lot of ways to go about doing this. One simple way is to bury a large section of steel culvert, either vertically or horizontally depending on size of configuration. You can also employ earthbags filled with the soil on site to create walls, especially if they are curved to resist caving in. A roof is a little more complicated in that you need heavy duty support with steel or wooden beams, reinforced concrete, or such.

 

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I specifically disclaim any warranty, either expressed or implied, concerning the information on these pages. Neither I nor any of the advisor/consultants associated with this site will have liability for loss, damage, or injury, resulting from the use of any information found on this, or any other page at this site. Kelly Hart, Hartworks, Inc.

 

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