Hybrid Questions and Answers Involving Papercrete
Kelly
Hart is your
host at greenhomebuilding.com, and
has built his own home using a hybrid earthbag/papercrete technique, which
can be seen on the Earthbag
page. He has adapted the concepts popularized by Nader Khalili
and his "superadobe" building, by filling the bags primarily
with crushed volcanic rock. This creates insulated walls that are similar
to strawbale, except that they are completely impervious to damage from
moisture, insects or rodents. The earthbags are plastered both inside
and outside with papercrete. Kelly has produced a video, titled Building
with Bags: How We Made Our Experimental Earthbag/Papercrete House, which chronicles the adventure of building this house, and shows
other earthbag houses as well. Another video program that he produced
is A Sampler of Alternative Homes: Approaching
Sustainable Architecture, which explores a whole range of
building concepts that are earth friendly. One of the homes shown in this
video is a hybrid strawbale/wood framed home. Kelly spent many years as
a professional remodeler, and is available to answer questions about what
he has done, or consult about other hybrid projects.
Questions and Answers
Earthbag/Papercrete/Steel Quonset Vault
Earthbag/Papercrete/Steel Quonset Vault
Q: Isn't a steel quonset hut redundant? Why not form the earthbags like Nader Khalili intended as an arch or dome supporting itself?
A: Good question. Actually, a large vaulted structure is extremely difficult, if not impossible, to create using earthbags. Nadir Khalili has never attempted it. The largest earthbag vault that I know of is one that I built as part of my house, as a mudroom entry, that spans eight feet at the base. The walls of this are some 30 inches wide in order to provide sufficient buttressing for the vault.
What Nader has done with his vaulted structures is provide the vertical, buttressed side walls using his Superadobe technique, and then created the vaulted roof with a form covered by stabilized adobe, I believe. This vault ends up being only about 6 to 8 inches thick. Also, his vaults span about 12 feet at the most...my workshop spans about 16 feet. Using the steel quonset as a permanent form/interior finish seems like the simplest, and sturdiest way to achieve what I want.
Q: Can another material be used for the vault form such as plywood?
A: I imagine that plywood would work to create a form also. I have made smaller arch forms by cutting the shape out of plywood and then attaching 2X4 (or greater) to the plywood, following the shape. The thing is, though, that wood means trees being cut, whereas much of the steel used these days is recycled. The Steen's light straw/clay blocks may be the most ecological solution to making vaults.
Q: Would like the source of the supplier of the metal quonset hut that Kelly is earthbagging and papercreting. Also wondering what the size of his hut (length, width and height). What is the gauge of the metal hut?
A: I bought the quonset kit (minus the end walls) from U. S. Buildings (www.us-buildings.com ) out of Florida. The nominal size is 16 feet wide by 34 feet long, and the height of the metal part is 11.5 feet (although I raised it to about 15 feet with the bag stem walls). The steel they used is relatively thin, but plenty strong once the shaped sections are bolted together. They probably say at their website what gauge steel it is. I paid $1,900 for this, delivered to Colorado, with two buckets of stainless bolts to assemble it.
Q: I noticed your Quonset hut project. I've been looking to do something similar. I intend to buy a modern steel span (www.americandurospan.com) and earth berm it. It'll be larger than the one you have and mostly arch with only a few feet of vertical wall. I've been looking at different passive solar designs, and I think I'll be okay with a solid concrete and rock pad on the bottom. I'm trying to figure out the exterior though. The shell will have to be strong, insulated, and water resistant, as I'll be living in a temperate rain forest. I've been thinking of 2" or so of ferro-cement for the shell exterior, with papercrete or light weight concrete for outer insulation. Do you think papercrete would have moisture issues? I'm worried about the expansion of the outer material since the rest of the building will be high density steel and ferro-cement, it seems like they might separate or have some other stress issues. I've also found little information on the strength of papercrete other than the demonstration on your site I'll be berming on both sides and one end, so it has to be very strong.
A: In looking at the americandurospan site, their quonsets seem to be very similar to what I used ( us-buildings.com ) . I would think you want to use the S-series true vaulted shape, as it is much stronger for supporting any kind of weight on top. By berming the sides you can add quite a bit of weight over the arch without distorting the shape. Mine is supporting about 50 lbs per sq. ft. I expect. There are definitely issues with moisture and papercrete...it has to be able to dry out if it gets wet, so sandwiching it in between rather impermeable layers (steel and concrete) might not be a good idea. Papercrete does not expand when it gets wet, surprisingly; it is quite dimensionally stable. It would loose its ability to insulate and can harbor molds if it stays wet and warm for too long. If your climate is sufficiently temperate, you might be quite comfortable by covering the entire vault with a layer of earth and be done with it. Plant flowers up there!
Q: How are you constructing the foundation for buildings like your carriage house?
A: Both my dome house and the Carriage House have earthbag foundations, that is the earthbag walls provide their own foundation. This may sound strange, but there is no other foundation for these buildings, and this is the way that Nadir Khalili has built many of his earthbag structures. This has worked well for me in my location, but I should add that I am building directly on pure sand in the desert southwest. In areas with heavier soils or more precipitation, I would recommend starting the earthbag walls on rubble trench foundations to avoid any moisture penetrating the walls or frost upheaval. Earthbag structures do not need a solid monolithic foundation for proper support.
Q: Rubble trench with or without bond beam? could you give me more information about the wall assembly of the steel quonset carriage house (what is the composition and what is the construction process for the walls?) It looks BEAUTIFUL, especially the marriage and separation of the materials.
A: For an earthbag wall, the rubble trench does not need a bond beam...for something like strawbale, this would probably be a good idea. The earthbag stem wall of my carriage house is made with two parallel columns of earthbags that are tied to each other by periodic straps of barbed wire, so that they cannot separate. A wooden top plate (wide enough to set the steel quonset panels on solidly) is then pinned to the stemwall with long sections of rebar. Before this plate is set in place, steel angle brackets are mounted at intervals to match the pattern of the quonset ribs, with the bracket hooking under the plate when it is in place on the wall. This allows the quonset to be firmly bolted to the plate, making the whole assembly connected. Then I stacked the earthbags over the quonset vault, being careful to tie the inside firmly with either cable or wooden joists at the spring line (the point where the vault starts to curve inward) before placing much weight up on the vault. At this same place, on the outside, some kind of retainer (I used lengths of 2X6 lumber) needs to be attached outside the bags and bolted through to the steel to keep the vertical column of bags from being forced outward and collapsing. If you look carefully at some of the images above this should make more sense. Once the bags were all stacked, I stretched 2" chicken wire over the whole thing before plastering it with the papercrete (could use stucco). The result of all of this an extremely monolithic structure that should last a very long time and is well insulated (I filled the earthbags with crushed volcanic rock, but they could be filled with styrofoam, perlite, or some other stable, light, insulating material).
Q: I looked at your quonset hut building; it was quite interesting. Do you remember what the manufacturer's rating for snow load was? I ask because that structure was obviously strong enough to cover completely with earthbags, and I'd like to figure out the amount/weight of
the rebar I'd need to match that rating.
A: According to the specs from the manufacturer, the building was designed for at least 50 PSF live load on the roof, 62 PSF ground snow load, 90 MPH wind velocity, and seismic zone 4. I should add that I reinforced the loading capacity substantially by firmly attaching wooden joists every 2 feet on the inside at the spring line of the vault. This could also be accomplished with tension cables across the inside.
Q: In your steel-shelled shop, how did you attach the joists (for the loft) to the steel shell? I have one of the peaked-style buildings (16' wide, 11'6" high at the peak) and I'd like to build some overhead storage.
A: I fabricated steel brackets that are bolted to the joists and also to the steel shell, using the same bolts that are used to attach the sections to each other.
Q: I assume the bracket just goes under a second nut on the end of the section bolt, and the joists are cut to clear the bolt ends.
A: You are basically are correct, except that I didn't use a second nut, I removed the original one and bolted the bracket tightly against the steel rib of the shell, and left enough clearance when cutting the joists to fit with the bolts protruding.
Q: I am considering buying property that would accommodate an airplane, i.e. private strip, plus a large hanger. My best idea has been to buy a ranch with a large barn, but my preference is to build something myself out of natural materials. I think that there should be a relatively simple way to get a round structure with high walls (possibly rammed earth), and then use steel roof framing over the top, utilizing it's lightness and strength. Will also be looking into the possibilities of an earthen base, and then creating an inflatable roof which is then sprayed lightly and repeatedly with concrete (or some other material). I believe that this is already being done, and seems to eliminate many of the complexities of erecting a large dome.
A: I recently constructed a building on my property that I call my Carriage House, that is a hybrid design that could be modified to be large enough for an aircraft hanger. It is basically using a steel quonset shell as a form to make an earthbag/papercrete vault. These prefabricated steel structures come in all sizes, and are actually used as hangers. They are relatively inexpensive and quite adaptable to accommodate various design modes. They can also be bermed substantially, or even buried completely if backfilled properly. You might think that steel is not all that "natural" but in my opinion this is a reasonable option because most steel is actually recycled, and the vaulted quonset shape spans large distances with minimal material.
Q: Has this been considered: build the typical quonset hut via US Steel or others with an insulated concrete slab that has the radiant heat tube for various methods of heating. Cover the quonset with straw bales. Cover the straw bales with a reinforcement material. Spray the reinforcement material with shot-crete. Paint shot-crete with an Elastomeric paint fitting to your environment. Build end walls with straw-bales and repeat the process of reinforcement and shot-crete. Your thoughts please!
A: The trouble with using straw this way to cover a quonset is keeping it dry so it won't rot. The steel shell will keep interior moisture-laden air from condensing in the straw, but while shotcrete and paint can do a good job of repelling moisture, it is not guaranteed. Any slight crack in the cement/paint layer can admit water, which would then not be able to evaporate and would fester in there forever; this sounds like a maintenance nightmare to me. A better solution, if you wanted to use straw this way, might be to attach wood stringers to the straw, and then use some other roofing material, such as metal, over this in such a way that the straw can still breath. I see no problem with using straw for end walls, as this is similar to any other strawbale building. Another approach might be to use an insulation material that is not vulnerable to moisture damage, such as the volcanic rock that I used, or even recycled styrofoam, packed into earthbags and then plastered over.
Q: I ran across your quonset hut experimental building and was very interested because it is similar to what we have planned. We have a 45x40 quonset hut 17' tall (unerected). We plan to use recycled styrofoam (from docks) cut into blocks and pinned together with rebar and stacked against the sides, then coat the whole thing with cement. If you have never seen the styrofoam they use to hold up docks it is sheets of styrofoam (the kind made of a lot of little beads)4 or 5 feet wide by 8 to 10 feet long (or cut to size). Each sheet is 10" to 12" thick. Two of these sheets are stacked and glued together to make a 20" to 24" thickness. When they eventually become water-logged they are pulled out and replaced with new. The old is then taken to landfills. Not an environmentally friendly solution. They eventually dry out and then are very light weight. It is very strong and super insulating. What do you think?
A: I think this sounds like an excellent idea...a great way to recycle waste styrofoam!
Q and A: We are from Hawaii and are currently working on developing an art center up on the North Shore of Oahu, where we recently purchased some land. We are interested in your use of steel arch buildings covered w/ papercrete, and would especially like to find out more about how you covered the structure. Did you spray it on like gunnite, w/ a wire mesh skin?
The papercrete plaster was applied by hand, with a 2" chicken wire mesh embedded. But the bulk of the insulation over the vault was created with earthbags filled with crushed volcanic rock.
What about other lightweight concretes, like those using foam and/or other lightweight aggregates?
There are other lightweight concrete formulae that could work.
I would like to incorporate about 4 of these structures w/ other freeform covered walkways, etc. to connect them together. These I envision also made out of some kind of lightweight concrete that we can make into interesting shapes. What would you suggest?
All of this sounds possible...it depends on the specific design what might be best.
Was permitting a problem for you?
No...we live in a county where this is not an issue.
We are in a rather rainy area of Oahu, and from the little I've read, it seems that papercrete absorbs a lot of water. If this is true, then it might not be the best material for us.
It is true that PC does absorb water, and for this reason might not be your best solution.
Also, as we are planning to build quite a bit, we need to find something that is relatively inexpensive but durable.
PC is inexpensive and quite durable from my experience, but probably not as durable as some of the mineral-based lightweight materials.
It is also important that we can mix the cement in large quantities and spraying seems to be the fastest and easiest way to cover 4 or 5 of these (20' high x 30'wide x 25' long)--have you ever sprayed any lightweight concrete?
PC has been successfully sprayed, as has some of the finer aggregate mixes I suspect, although I don't have personal experience with this.
Or is it rather quick and easy to trowel on?
Like I mentioned earlier, we applied the PC just as a plaster over the earthbags, so we simply bucketed the slurry to where it was needed and smoothed it out by hand.
Was weight a problem for you (i.e. the weight of the earthbags along w/ the papercrete--what was the load bearing capacity of your steel arch building?).
Yes, this is a major consideration, and one that the manufactures of the steel buildings will warn you about. The buildings are designed for a certain snow or wind load, and they don't want you to exceed this. What I did to counter the additional weight was reinforce the structure internally with either cable or joists installed at the spring line. I have some plans for sale that detail these attachments: http://www.dreamgreenhomes.com/plans/carriagehouse.htm
Q: I am a student of environmental architecture at the Centre for Alternative Technology in Wales. I am writing a paper on the prospects of earthbag architecture in the mainstream. I am really impressed by your Carriage house design. Could you please estimate the total cost, man hours and dimensions of the carriage house?
A: I appreciate your interest in the Carriage House design. I have actually drawn it out, so you can see for yourself what the dimensions are at http://www.dreamgreenhomes.com/plans/carriagehouse.htm
As far as cost and man hours, I will have to estimate, since I didn't keep accurate records of these. I believe that the cost was under $5,000 U.S., with the steel building being about $1900 (delivered with bolts, but no end walls). Much of the material I used to build it was recycled, including the bags of scoria (recycled from the building shown at http://www.greenhomebuilding.com/earthbag.htm#Matts ), the framing wood for the end walls (from a dumpster at a neighbor's building site), the cedar lap siding (remnants sold at discount), and the windows. Wood for the second floor joists and flooring were new. The cost of the papercrete was negligible. I did hire a couple of Mexican roofers to help put up most of the earthbags and papercrete on the vaulted portion, and some neighbors helped stack some of the bags and pour the concrete floor. I worked periodically on this building for about two years, whenever I had some extra time. A wild guess would be around 1,000 man hours.
Q: Can you provide approximate costs for building the carriage house?
A: I can tell you that I spent about $5,000 to build mine, but I was lucky to get an exceptional deal on the metal vault, found recycled materials for most of the other components, and did most of the work myself. I am guessing, without actually costing the parts and labor, that it could be built for around $20,000.
Q: I was intrigued by your quonset type garage on a raised earthbag foundation. I have such a structure, 20 x 30 which is not yet set up because I've balked at the cost of the concrete foundation. How was the 2x10 board fastened to the earthbags. I want to set mine right on the ground and find some means of holding it together rather than grouting it into a concrete trench on a 20x30 slab. Any advise would be appreciated. Wind is a concern here in North Dakota.
A: There is a cross section diagram of how my Carriage House was assembled at http://dreamgreenhomes.com/plans/carriagehouse.htm . It might be a little hard to see. Basically, the steel quonset is attached to the 2X10 with a heavy L bracket that goes under the wood and is screwed into the wood and bolted to the steel. The board is then pinned to the earthbag stemwall with 5/8" rebar pins going all the way to the ground at about 4 ft. intervals. Then, the whole thing becomes monolithic with the stucco netting and papercrete or stucco plaster on the outside over all of the earthbags. I would suggest that you raise the 2X10 up off the ground a foot or so on earthbags, so that it is away from the dirt and so that you have some hefty weight to counter those North Dakota winds.
Q: I'm considering using a quonset style steel roof (1/3 Arc 28' span) on a 8' high poured foundation. Using the roof as a braced form for a reinforced concrete shell 3"thick, leaving it in place as part of the ceiling. Any thoughts?
A: I have two comments about what you are proposing:
1) It will be essential that the base of the quonset, at the level of the concrete foundation, be substantially braced with either cables or joists that are adequately connected the the steel structure. This is to withstand the outward pressure created by all that weight from splaying your foundation. This is true even without the additional concrete.
2) A concrete shell poured over the steel will not provide any real insulation from heat and cold, so unless you live in a very temperate climate, the space will not be comfortable for occupancy much of the time, without further insulation. In fact I don't really see any advantage to pouring such a concrete cap, since the steel shell itself is plenty strong.
Q: I am interested in using papercrete to insulate the inside of a arched metal quonset style building. It sounds like spraying the material on is possible. Has anyone tried using a drywall texture gun to spray it? The building will be used as a shop and storage area for equipment and vehicles, and I don't want everything covered in rust. Would something like gypcrete work better in this type of application, or is it a sponge too?
A: People have successfully sprayed papercrete, but it can be difficult; the pulp tends to clog nozzles very easily. I don't know about using a drywall texture gun. One type of sprayer that would likely work was designed for ferrocement applications. It has an open hopper that air is forced through to spray the material. This has been used for various earthen materials as well. You can see these at http://ferrocement.net/cgi-bin/shop/i-shop.cgi under "sprayer".
A larger issue might be getting the papercrete to stick to the smooth metal. It might work to spray a light coating of something that has better adherence on first to give the papercrete some "tooth" to hold onto. Or you could somehow fasten stucco netting to the metal shell using the existing bolts.
Gypcrete might also work in this application, but it won't give you much insulation. I doubt that either would have problems with moisture once they are cured. The papercrete will take much longer to cure, and the building will have to be left as open as possible for this to happen; during this time it will be very humid in there.
A whole other approach to insulating your quonset would be like I did for my Carriage House. See this page or http://dreamgreenhomes.com/plans/carriagehouse.htm for a description of this.
Q: I am strongly considering an interior insulated quonset hut for living space. Would there be any condensation concern from spraying icynene on the inside? (northern Alabama climate) I'm also especially curious if there is a spray on fireproofing for this insulation that could also serve as the finished surface .... something light enough to be sprayed directly to the foam without any additional support besides the steel-icynene bond?
A: I wouldn't expect there to be any problem with condensation with what you describe. It is fairly common to spray metal buildings with interior foam insulation. As for the fire proofing, I don't have any information about this. You might ask some of the specialists who do this sort of work if they know.
Q: My husband Mike and I are planning to erect a steel quonset style building on our land near Westcliffe, and insulating it as you did the carriage house. Have you seen any indications of degradation of the scoria bags or papercrete in the years since completion? I want to go in to this with my eyes open, and attempt to mitigate any future issues right off the bat.
A: I have been very pleased with how this hybrid steel quonset/earthbag/papercrete building has worked out over the last few years. The only degradation that I have noticed is a slight flaking of the very exterior surface of the papercrete. At some point it may be necessary to put a more durable coat of stucco over it...or this could have been done when I originally constructed it.
Ferrocement/Papercrete/Tile
Q: My husband & I are looking into building a ferrocement dome (modular units). What do you feel is the feasibility of sandwiching a layer of papercrete blocks between 2 layers of ferrocement? Since we are potters, ultimately ceramic tile and grout will be used for the finish. The wall would probably end up over 12' thick. I am aware that papercrete wicks moisture. Will this effect the ferrocement? I envision the dry papercrete wicking moisture too quickly from the outer layer of cement as the cement is applied. Then again. if the papercrete is moist as the last layer of cement is applied, will the papercrete ever have a chance to dry out being stuck between two layers of ferrocement?
A: It is an interesting concept that you propose. There would certainly be advantages to the arrangement, if it could technically be accomplished. With the ferrocement on the inside you should get plenty of thermal mass, and the papercrete would provide the insulation. The trick would be to get the papercrete to dry out after you poured the final coat of cement, and this might be quite difficult; some formulas of ferrocement are virtually water proof. My suggestion might be to forgo that final coating of ferrocement, and allow the papercrete to be the outer layer. This papercrete could be done in a couple of pours, so that the first one is highly insulating, with mostly paper and little mineral material. The next pour could be more much more sand with the paper and cement, to give a more durable, fireproof layer. This is basically what I did with my house, and it has worked out well. If the initial ferrocement shell is mixed to be waterproof, then you could simply allow the papercrete layer to breath and evaporate moisture as needed. Sealing it to moisture would be another option, but any water that does manage to get through might be trapped there for some time. This might take some experimenting, perhaps trying it unsealed at first, and the sealing it later if this seems necessary.
Tire/Papercrete
Q: I have been thinking about all of the different types of alternative building materials. Two of the materials that I am interested in are tires and papercrete. My first question is, is it possible to combine these two materials? By this I mean, can I build a structure with tires and fill them with papercrete? My thought is that I want to produce a structure that uses inexpensive materials and that I can build myself. I also want a solid structure that would provide a good insulation from the outside environment. Can you give me your thoughts on my idea? Is it feasible? What would be the downside of this method?
A: I wouldn't recommend filling tires with papercrete for several reasons:
1) It would take forever to cure, since it couldn't dry out very well in the tire.
2) For the same reason, it could become moist and harbor mold over time.
3) Papercrete does compact with enough weight on it, so this might be an issue.
4) Earth is much cheaper and easier to come by for filling the tires.
On the other hand, I would think that papercrete might work quite well as a plaster to cover the outside of a tire wall.
Q: We are hoping to build an above ground hot-tub using tyres as the walls. I am concerned that if I fill them with earth the thermal mass will soak up all the heat from the water and I am struggling to think of a suitable material which will provide both the mechanical strength and thermal insulation required (both below the tub and in the walls) (I've not found a supplier of pumice in the UK). Do you have any suggestions or know of anybody who has undertaken a similar project that I may contact? Would papercrete be suitable and if so what slab thickness would you suggest?
A: You are right about the mass in the tires filled with soil soaking up all the heat from the tub, unless there is some form of insulation between them. Papercrete does indeed act as good insulation, but only if it is kept absolutely dry, which may be a challenge in such a situation. In fact if the papercrete stayed wet and warm long enough, it could support mold, which definitely not be good. I am planning to build a hot tub using a plastic stock watering tank to hold the water, then placing some insulation (possibly pumice, fiberglass, or styrofoam), and then doing mortared rock work around it. Making such a tank with completely natural materials is a challenge.
Wood/Straw/Papercrete
Q: I want to build a permanent tipi using tamerack poles. Could I cover the poles inside & out with chicken wire, sandwiching flakes of straw in between, & plaster the whole thing with papercrete?
A: This seems like an interesting idea that might well work, especially if you live in a relatively arid region. The main concern would be moisture possibly wicking through to the inside. I know of straw bales being successfully plastered with papercrete, so this should work. I would suggest that you make sure that the straw is thoroughly stuffed between the wire and poles, so that at no place is the papercrete solid from inside to out. If you try this and moisture does seem to be wicking through, you could try to seal the exterior papercrete with something, but this is not always easy to do. This would be an experiment... but one worth trying. Let me know how it works out.
Q: I'm looking for a light weight natural material that can be used as insulation for a timber frame interior wall. Also be able to render over it without using gyprock. Looking at the papercrete idea and wondered if you may be able to recommend a recipe.
A: (Kelly) I suppose that you could use papercrete fro this. I would suggest making blocks first and allowing them to dry thoroughly before installing them as infill. The most insulating recipe is 50/50 paper and cement by dry weight, and the amount of water doesn't really matter...just enough to make the slurry. This is for "pure" papercrete, without sand. If these blocks seem too soft for your needs, you can add some sand to the mix. but this does reduce the insulation value. You could also use earthbags (polypropylene bags) filled with crushed lightweight volcanic stone, perlite, rice hulls, or recycle styrofoam, then line this with a plaster mesh before rendering.
Earthbag/Papercrete
Q: I am thinking about taking Nader Khalili's course on super adobe roll (earthbag). How does papercrete do in wet climates(OR)?? Can papercrete be blown on to interior wall for extra insulation?? I' ve heard it is hard to get building permits for earthbag constructed dome homes?? Also, is it hard to get bank loans for earthbag dome??
A: Nader is the expert on Super Adobe, since he basically invented it. His workshops are good, but expensive. How papercrete does in a wet climate is somewhat unknown, but I would think it might need to be sealed to avoid moisture problems.
Yes papercrete can be blown on the interior, if you have appropriate equipment for this. It does increase insulation, but you generally want insulation on the outside. As for building permits and financing, this is variable. Nader has been working on the permit issue for many years, and might be able to advise you. We got a mortgage on our earthbag house, but it was with a rather enlightened local credit union. Good luck with your project.
Q: I'm involved with real estate and rentals homes. I have found in my experience the most bang for your bucks is to stop the transfer of air between interior/exterior with modern doors/windows and vapor barriers however you risk having unhealthy houses and mold. New house construction isn't much better and the quality of work fluctuates greatly from contractor to contractor. Therefore I knew for some time nobody has a better motive to build a quality house for me than myself. I see you have built an earthbag shelter covered with papercrete. Since your earthbags are encapsulated now and the rammed earth can't breath I would think your earth could dry out and fail compression (like they did in New Mexico and that village church in Mexico), but then again the papercrete should hold the structure, right? I also wondered why you didn't attempt to waterproof the papercrete?
A: I didn't use rammed earth in the bags...they are filled with crushed volcanic rock, and then covered with the papercrete, which is NOT sealed from moisture...in our climate it does not seem to be necessary.
Q: In your own home wouldn't it be prudent now to cover the papercrete with something like bituthene or ferro-cement?
A: I really prefer a breathable wall, and after several years, I haven't had a drop of water come through!
Q: We were planning on building a house out of papercrete but with the moisture issue on contact with the ground is it possible to build the first floor out of earthbags, then the second level out of papercrete? That would solve the problem of papercrete no being strong enough too support 2 stories. If this is possible how would you install the floor joists on top of the earth bag wall and then the papercrete?
A: Yes, what you propose is entirely feasible. There are several ways of attaching floor joists to earthbag walls. One approach would be to create a reinforced concrete bond beam at the top of the earthbag wall and anchor the joists to embedded anchors. Or another approach would be to create an alternative bond beam with metal or wood plates in a manner similar to what is explained at http://earthbagbuilding.com/articles/bondbeam.htm. In either case I suggest that you continue up above the joists with a course or two of earthbags (possibly filled with gravel) so that the papercrete is not resting on wood.
Q: I am curious if you were to build the earthbag/papercrete home again, what might you do differently? Stabilize the scoria? Still use papercrete?
A: There is very little I would do differently really. I would not stabilize the scoria, as that would likely diminish its insulating value. I might not use the papercrete again, as it turned out to be not as durable as I hoped, especially in areas that were subject to direct weather. The folks who bought that house, at my suggestion, subsequently applied a standard stucco finish to the exterior. I wouldn't build an elliptical dome again; better to keep the shape circular.
You said you advised the new owners to use standard stucco. I was under the impression that was not a good idea due to breathability. True or false?
It's a compromise; ideally you want breathable walls, but these are difficult to attain in a dome without a solid roof to shed water. For awhile the papercrete provided breathable protection, and it absorbed most of the moisture and kept it from penetrating the rest of the wall, but it didn't hold up well enough. The interior remained breathable however, with its papercrete and lime plaster.
Container/Papercrete
Q: I live in Santo Domingo, Dominican Republic, which is as hot as Florida, and I need to insulate a shipping container for living. Can I use papercrete?
A: You might be able to use papercrete for this since it is insulating (about R-2/inch), but it will have to be keep dry with another roof for it to work very well.
What about the wall, can I use it outside and inside the container?
Papercrete could be used either inside or outside on the wall, especially if some wire mesh or some other method of physical attachment were used. On the inside would be the added challenge of getting it to dry out and also the fact that it would take up your valuable space.
If I don't have the sprayer, can I cover the container with other way?
You can apply papercrete by hand. Again it would be easier with some mesh to hold it in place.
