Site Preparation for Earthbag Buildings
Questions answered by Kelly Hart

Q: I have decided to build an earthbag structure similar to Riceland. The land I am contemplating building on is in a hilly area. Is it easier to excavate a flat area or can I integrate the slope of the land in my foundation & structure?

A: I suggest that you excavate a flat area so that you will have a level floor inside. You can probably use the excavated soil to fill some of the bags.

Q: I intend to build a earthbag house of approx 800-900 sq. ft. on land which is overlooking a beautiful lake. But there are lots of wild bush/trees which obstruct the view. Can I build earthbag house on an elevated platform / terrace with pillars made of concrete to hold the weight? An elevated house will give a superb view and also the remaining space can be used as terrace or elevated patio.

A: I suppose that with a sufficiently substantial and well-engineered platform that it would be possible to do this, but it sounds like a lot of trouble and expense to me. A simpler approach might be to elevate the home by creating an earthbag stemwall that is filled with soil on the inside to provide the platform for your house at the level you want. This would provide a solid foundation without so much expense and trouble. You could still build an elevated deck outside that wouldn't have to be nearly as heavy duty.

Q: I'm planning to build a house in Paraguay, South America. I got a piece of land and thought of earthbags as building material, as the climate is very humid and extremely hot. Now, the land has several springs. Moisture, if not water, just comes out of the ground. I wonder if earthbags are really the right decision and, in that case, how should I insulate the floor and walls.Can I go for earthbags on an extremely humid place, where I can actually have water running under my floor?

A: If your floor level is raise above the surrounding grade and you have a layer of about 16 cm of gravel below your actual floor, I think you would be safe from water coming up into your house.

Q: I am trying to find the simplest, low-cost solution for building on my site, near the mountains in Romania on a well compacted clay and sand soil with very little slope. I have drain channels build on the entire area, because the water does not drain in the soil, and so there is no water in my soil (as the geologist said). We have rain in the summer, and we have a long winter, big snow and cold winds. The temperature in winter are about -5F, and the frost level is at 3.5 feet. We are on a very low budget, and I know that sandbags are not the first choice for cold climates, but because that is what we can afford, I would like try to take a chance and try to make the best of it. I have some ideas, like: 1. Buried sandbag structure, just below the frost level, for better thermal comfort, but: How do I avoid flooding ?

A: You would need to provide a swale around the house to drain surface water away. And I would advise installing a moisture barrier on the outside of any bermed walls to keep moisture from entering.

Q: I own a little land on a flood plane, and I've seen very little on how earthbag structures deal with flood waters. Many sources say that the homes resist flood, but I would like more detail. I plan to build a structure on the uppermost part of the property so as to avoid as much of the water as possible, and I assume that such a structure would be able to withstand up to two feet of floodwater, but are they durable enough to go through such a natural disaster every five years or so? I would rather not rebuild every five years, which is why natural and sturdy Earthbags seemed so perfect. Any suggestions?

A: Probably the very best approach to preparing a house for regular floods is to build on stilts that are attached to well-anchored piers, so that the house is simply out of reach of the potential flood waters. This is what people have done for millennia, but this is not a good strategy for very heavy earthbags. Beyond that, the next best thing to do is build with materials that are unaffected by moisture if they do get wet, and earthbags certainly have this potential. After all, sandbags are used universally for flood control.

What you would want to do is follow all of the precautions for avoiding moisture intrusion into the walls, and this includes having a rubble trench foundation with a French drain that empties to daylight. Then you want several courses of gravel-filled bags that will not wick moisture upward, followed by bags filled with either stabilized earth or other materials that are not adversely affected by water. In addition to building on the highest location on your property, you can increase the floor level by making an earthbag stem wall several feet high which is then filled with soil to raise the floor level.

Q: How to prepare a building site, which is on solid, lava rock with a steep slope?

A: To build on solid lava rock that is inclined you might have to build up a perimeter stemwall with earthbags to create a level base for your house, and then fill this in with soil to make the floor level.


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