Building Components with Earthbag Building
Questions answered by Kelly Hart

Interior Walls

Attaching a Roof
Stairs and Ramps
Hanging Pictures and Cabinets

Interior Walls

Q: Is it possible/recommended to use earthbag construction for interior walls?

A: You can certainly use earthbags for interior walls, but bear in mind that they do take up that extra space, and that if there is going to be much plumbing in the wall it is often easier to use conventional wood framing.


Q: How is the electrical done?

A: Electrical wire can be routed between the bags before they get plastered, either with conduit or using UF wire accepted for direct burial.

Comment (Owen):  Here's an easy way for mounting outlets.  You can add just one piece of plywood to the side and place it at a butt joint.  Nail or pin it into the end of a bag.

Response from Kelly: When I was ready to install electrical boxes in my house in Crestone, I simply drove some long pointed wooden stakes into the bags where I wanted them and left enough sticking out to screw the boxes to. With the scoria this was easy to do and they were plenty firm. This may be harder to do with some soils, especially if stabilized. Once the stakes were driven in they were amazingly firm and did not wobble, and of course the plaster holds them even firmer. Your method and Kaki and Doni's are likely more certainly secure, but the stakes have the advantage that they can be done later, when you might be more sure of where you want them.

Q: What in your experience is the best way to handle things that are sunk into the wall in conventional construction, like light switch and electrical outlet boxes, or the various fixtures that are usually anchored into studs?

A: There are a variety of ways to handle such fixtures, and several are outlined at our blog: earthbagbuilding.wordpress.com


Q: How is the plumbing done, assuming that you tap the city for water/sewer?

A: Often it is easier to route plumbing into wood framed partition walls inside the house, and otherwise route drains and such under the floor.

Q: Should the plumbing be stubbed up in the floors or should it come from outside through the walls?

A: In my earthbag house I brought the primary water line in below frost level and then up to connect with plumbing in a framed interior wall. This avoids any issues with freezing pipes.

Q: I am interested in building an earthbag home. My question is about plumbing for the toilet and shower. How is the toilet plan setup and where does it drain to?

A: Typically the plumbing that you describe would go under the floor, in the ground, and be set in place before the wall building begins. The black water from the toilet needs to drain to an appropriate septic tank or sewer line. The shower drain could be plumbed into a gray-water tank for possible re-use if you want.

Q: I am considering a strawbale with an earthbag foundation. I live in Illinois...cold winters wet spring. My question is, can I use a radiant heat system between the earthbags?

A: Radiant heat works best when imbedded in a solid thermal mass floor, such as adobe or concrete. If you want to embed radiant heat tubes between the earthbags, this might be possible, but I am not sure how well it would work. The bags would have to be filled with good adobe soil and well insulated on the outside.

Q: I am nervous about plumbing and earthbag walls - Paulina implies it can be done, but her description is fairly brief.

A: I actually used wood framing in the wall between my utility space (with washer and dryer and water heater) and the bathroom, because there was so much plumbing to fit there that it was far easier to do that. On the other hand, you can run water lines in the cracks between bags and even through bag wall (either by leaving larger pipe chases or even pounding the pipe through wall later)...so you can go either way.

Q: When you put your water plumbing into the house from outside, is there some trick that I need to know?

A: I placed mine underground below the frost line to enter the house, and then came up through the floor where I needed it. If frost is not an issue, then it would be possible to just poke the pipe directly through the wall while you are building it, or even pound a section of steel pipe through after the fact.

Q: What would options be to keep utilities out of concrete while using earthbag stem walls? I'm curious if one could run the utilities alongside the interior stem wall and floor while hiding it in an isolation box/large moulding.

A: I usually advise that people keep plumbing out of earthbag walls, except to just penetrate from one side to the other. This leaves either under the floor or in interior cavity walls for the plumbing. Your idea of having a chase for the plumbing disguised as molding certainly seems feasible to me, as long as you construct it in such a way that it pleases you.


Q: What is used for the slab inside the the outer walls? I have no idea of what would work other than concrete. If there is something else will carpet or tile be able to cover it? 

A: A concrete pad is certainly one option, but is not the only one. The floor could also be made with flagstone, brick, pavers, poured adobe or rammed earth. Carpet could be laid over any of these, but tile would need a solid concrete base most likely.

Q: For the floor, instead of doing a cement footing, could one not insert floor joists after the second or third row of bags? One joist where the bags join on one course of bags? This would create a floating floor of sorts and underneath could be filled with any sort of recycled insulation material. Then no cement at all would be required for the foundation. Floor joists would be 15cm tall so maybe it would be two courses of bags to reach that height before going back to an alternate row... think it would work?

A: Sure, you could do that. I basically did the same thing when I framed joists for a loft in earthbag domes that I have built. You might want to place a horizontal plate for the joists to rest on so that they will be level and the bearing weight of the upper story will be more spread out.


Q: What do you recommend for the most economical nice looking roof for a rectangular 1500 square foot home?

A: All of the standard roofs that are used with conventional homes can be employed on a home with earthbag walls. One of the least expensive and ecological is actually metal roofing, since it can be made with minimal framing and much of the steel is recycled these days. You would still need to insulated the roof from below in some way.

Q: My mother and I live together. I want to build an earthbag home in Utah. My mother is ok with it as long as its square. I want an earthen roof. We live in an earthquake zone. Domes seem the only possibility. She won't accept domes. Vaults on the other hand, seem ok with her. Is there a way to make it work? Maybe buttresses or additional inner vaulted arches set periodically, or even a compression ring?

A: Actually it is hard to create an earthen roof with domes. Kaki and Doni (authors of the Earthbag Building book) actually tried this (in Moab, Utah see earthbagbuilding.com/articles/honeyhouse.htm) but eventually gave up because it was too hard to maintain. Another example of earthbag building in Utah is a Ranger Station that is rectangular (see earthbagbuilding.com/projects/ranger.htm). There is no reason why you can't use earthbags for the walls, similar to that project, and then make a more traditional earth-sheltered roof. We have quite a few earth sheltered plans shown at dreamgreenhomes.com and many of these can be built with earthbags.

Q: I would like to know about building in damp, climates that have large snow run offs in spring and roofs incorporating earthbags.

A: Most roofs that incorporate earthbags are going to be domes of some sort. Earthbag domes perform best in more arid environments because waterproofing an earthbag dome can be problematic. It is possible but any minor leak can cause problems, and it is difficult to eliminate this potential. It is best on a damp climate to have a roof with a good eave to keep moisture away from the walls.

Q: Would earth bag buildings succeed on the damp northern California coast?

A: Yes, you can build earthbag buildings in your climate. I would recommend vertical walls with good eaves on the roof to help protect the bag walls.

Q: How to make the flat roof in earthbag buildings?

A: A flat roof would need to be constructed with, as in any wall system, some means for providing support for the spans employed and then an appropriate waterproof membrane. This could be done with wood, steel, or reinforced concrete.

Q: I am thinking that instead of a flat roof we need to have a slight slope. We will have 18" overhangs on the roof, but shouldn't we have maybe 1/12 pitch (1" for every 1')? Or is that not enough?

A: I agree that a pitched roof is a good idea, and 1/12 should be plenty, especially if the roof is metal. Sometimes shingles need a steeper pitch.

Q: A square-shaped house measuring 50ft one side, is it possible to pour concrete roofing slab. I mean if the earthbag construction will be able to withstand the casting of a 20-30cm thick concrete slab for a roof?

A: Earthbags when filled with mineral material can bear very heavy loads, especially if they are reinforced properly and have hefty bond beams on the top of the walls. You will need to check with a qualified engineer to determine the specifics of the example you mention.

Attaching a roof

Q: How does the wood roof attach to the bag wall?

A: I assume that you are referring to a conventional wood framed roof over vertical earthbag walls. The specific details of such an attachment would depend on the exact circumstances, but there are several ways that I can imagine. A top plate of either wood or a reinforced concrete bond beam can be attached to the bag wall with embedded rebar pins or poly straps or bands that loop around several courses of bags and the top plate and are cinched down to anchor the plate to the bag wall. Then the roof rafters or trusses can be attached to this in the normal manner.

Also, I attached large log vigas that support a loft in an earthbag dome by drilling half-inch holes through them where they intersect the bag wall and driving long (~ 24") half-inch sections of rebar through the poles and into the center of the bag wall. These vigas were simply resting on the bag wall, which was bearing their weight.

Stairs and Ramps

Q: Have you seen any plans that would work for a wheelchair ramp made of earth bags? The house level is about 4 foot high. My wheelchair bound grandson is now with me. I am also disabled. This is the only construction I think I could manage, physically & financially.

A: I have made steps with earthbags, but have never tried to make a ramp. Stacking bags naturally creates a stepped shape because of the discrete bags. If you want to make a smooth ramp out of this, you would have to fill in the steps with concrete or something like that. Or I suppose you could make a stepped form with earthbags, and then cover this with wooden boards or metal to make it smooth....but that sounds like a lot of work that might be easier done with entirely wood or metal. Or, here is another idea: suppose you created two stepped earthbag walls with a space in between them that was then filled with earth, tamped as a ramp and covered with a few inches of concrete? Something like this might work.

Hanging Pictures and Cabinets

A: Upper kitchen cabinets - are they installed on the walls in a special manner?  They could be fairly heavy with dishes, cups, etc.  Don't know much about installing cabinetry, but I'm wondering about anything installed on the interior walls.  Normally, you find a stud and pound in a nail or screw in a screw.  Won't installations on earthbag walls make holes in the bags within?  Does this cause problems, and will heavier items be stable?

A: That is an excellent question about how to attach cabinets to an earthbag wall. The answer, to some extent, depends upon what you fill the bags with. If you were to use an adobe-like soil that contains some clay, then you can actually use very long screw that will hold quite a bit of weight. With other, looser soil or material, you need to use another strategy. You can easily pound long sections of threaded rods all the way through these bags, and then bolt sections of wood (even 2" X 4" s) on both sides, that are very secure. If they are long enough, a whole row of cabinets can be hung on them. Piercing the earthbags, even with such loose material, is not a problem. I filled the bags of my earthbag house with scoria, a type of crushed volcanic rock, that provides excellent insulation.

Q: We have a large number of framed photographs of our forefathers / gods to which we pay our respects often . We have to have electrical fittings / plumbing fittings which require to be fixed on the wall. Since we don't get good quality PVC pipes / fittings in our area, we often have leaky taps / joints which are to be serviced every now and then which makes closed / consealed piping undesirable.

A: When I built my earthbag house I drove large wooden stakes into the walls wherever I wanted to attach electrical recepticles and then screwed the electrical boxes to these. You can also attach longer pieces of wood with wire or  twine in any area where you think you might want to hang pictures. As for plumbing, I tended to place the bulk of it in hollow wood-framed interior walls which allowed access, or just drove the pipe through a wall when necessary to go from one side to the other.

Q: On a completed house, will the walls be safe to drill or put nails into for some interior decoration?

A: How to attach interior fixtures depends partly on what the bags are filled with. If you are using a solid adobe-like soil, then you might be able to use long decking screws to make some attachments. Otherwise, you might need to imbed wooden anchor boards or stakes into the bag walls to give you something to screw or nail into. It is also possible to pound long threaded rods all the way through a wall to secure heavy items.

Q: I was wondering how much weight can a standard earthbag wall support? Is it capable of supporting, say, kitchen cabinets? Are there special anchors needed or will standard wood screws suffice?

A: Earthbag walls can support a great deal of weight if the attachments are done right. Standard wood screws are not up to the task if screwed directly into the bags; you need to embed wood or steel into the wall where you want to hang cabinetry. This can be done either at the time of building the wall, or it can be done later by simply driving stakes into the wall. This might be easier done in places where there is already a slight void, like between bags or courses of bags. Another way of anchoring is by pounding threaded rods all the way through to the other side and putting large washers there to hold the rod in place.


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