Sharing information and promoting earthbag building
|Possible Hazards in Earthbag Building
Questions answered by Kelly Hart
Q: Can you please advise me how rodent proof is earthbag construction. In an area where there has been considerable drought, would the bags themselves be an attractive way of getting nesting material?
A: Most earthbag construction is inherently rodent proof, much more than strawbale, or stick frame construction is. The mineral material filling the bags is not attractive to such critters, and the bags themselves are usually not accessible because of the plastering material. We have had NO mice coming through the walls of our house.
Q: My husband and I are planning to build our home out of sand bags. We have virtually no budget and were planning to use either the dirt on our land or silica sand. It must be strong enough to withstand anything a tornado might throw at it and we feel it will. Our BIG problem is fire ants. I am allergic to the bites and we need to know if they can or will live or get into the walls using either of these materials.
A: Ants do live in soil, so this possibility couldn't be ruled out; I would expect that this situation would be very rare, and could be dealt with in a variety of ways to kill the ants if they started to establish a colony.
Q: I was wondering how to prevent the bags from becoming infested with all sorts of ants and pests?
A: Clay/sand soil will form a solid block like adobe. Either this or cement-stabilized soil is not so attractive to ants and other pests. Also, the bags are well plastered both inside and outside to form an additional barrier.
Q: The area my friend wishes to build on is prime scorpion habitat, not to mention the ever-present fire ants that love building nests in dirt. How do you keep earth-dwelling insects out of a house made of dirt?
A: The polypropylene bags have a pretty tight weave, so this alone will keep scorpions and some ants out. The first few courses of bags should be filled with gravel, which does not attract ants, and then with a good exterior plaster (perhaps lime), I don't think ants will be much of a problem. If they do appear, there are ways to exterminate them...so I wouldn't worry too much about this.
Q: I live in Florida and we have Fire Ants. I just worry that the ants would love these types of houses and infest the walls and make it into a giant ant hill. Have you ever had anyone have problems with that? I know you could probably spray bug killer but I can't do that ifIi am gonna have my goats in them.
Q: I want to know if you have any difficulty with weather damage or pest damage and control? Do you treat the bags with anything to prevent rot or pest infestations?
A: The problems you mention are not common. The plasters used on the outside are best stabilized so that the weather does not harm them. Pests are rarely attracted to the materials used in the bags, which is mostly earthen, mineral materials. It is possible to treat the soil with borax to resist most pests, but this is usually not necessary.
Q: Rice hulls are definitely available here, but I'm a bit afraid to use them, for fear of insects or rodents getting into them. I know rice hulls don't have much food value, but wouldn't they make good nesting material? I suppose if I used soil in the bags for the first several courses, then rice hulls on top of that, and plastered it with stucco mix, the critters would not be likely to get in. What parts of the world have rice hulls been used in? I'm in an area that tends to get torrential rains from time to time, and winters are not very cold, so there are always critters around, trying to get in.
A: I suppose that mice might nest in rice hulls if they had access to them. You would definitely want to raise those bags well off the ground with bags of gravel or volcanic stone (which is very lightweight) first. I think that rice hulls have been used as insulation in many localities, including Tennessee. It is important to maintain a good solid plaster over the bags, just as it is with strawbale building.
Q: Are these materials resistant to fire and insects?
A: Most earthbag buildings are completely fire and insect proof. Mine is covered with papercrete, which is fire resistant, but which will smolder if it gets hot enough. To mitigate against this, I put a lot of sand in the final coat of papercrete on our house, which makes it much more fire resistant.
Q: We are building a community in Ghana- Africa and I was considering using earthbags. This region has a huge problem with Termites, do you know if the bags will stand up against these bugs?
A: As far as I know termites find polypropylene indigestible. At least I have never heard of anyone having a problem with this, and there have been a number of earthbag buildings completed in Ghana and other regions with termites.
Q: On your Web site you say earthbag is bulletproof. Where is the proof? This is not an idle question. There have been a number of murders here recently that could have been prevented had the people been living or studying in bulletproof structures. There is interest here in building with earthbag for this reason, but first I am checking with you to see if you are aware of any ballistic tests that have been conducted on earthbag walls, and if the results are published, where I could get them. Thanks very much, from the war zone in Israel.
A: This is a very good question. I only inferred that sandbags are bulletproof from the fact that they have been used to barricade military encampments at least since WWI. I'm sure it makes some difference what the bags are filled with, how impervious to bullets they would be. I suggest seeking some military training manuals for more information about this.
C: I would like to congratulate you for your contribution to the world's various societies on this construction technology. I am living in East Africa. Let me tell you something. The villagers of one remote area had difficulty in constructing concrete buildings because the sand in the area was too salty for Portland cement applications. Their houses made of mud and wood were unstable and they were frequently becoming prey to wild animals, i.e. leopards and lions. Using information from your web site, I managed to construct a circular earthbag house roofed by corrugated iron sheets. This technology was appreciated and many villagers applied it for their houses and the problem of man eaters was solved. I then thought that it will be good to return our thanks to you for saving the lives of many villagers. Although we do not have money to pay you back...but God will reward you.
Q: How do you go about protecting earthbag houses from hurricane damage?
A: (Owen Geiger) Use 12" roof overhang and roof anchors as recommended by the Florida building code for hurricane resistance. Add strong window shutters so the wind can't get inside and lift the roof off. To secure the roof you need a good reinforced concrete bond beam at the top of the walls that is well connected to the bags. Add rebar pinning down through the bags about every 3', including next to all doors and windows. It's good to add vertical strapping (poly cord, etc.) every 4' or so that wraps around the entire wall and bond beam. Cement plaster is strongest. Gravel bags on lower courses help resistant flood damage. Round shapes are strongest but cultural preferences typically prevail. Adapt good building methods and things will work out.
Q: Is the reason why earthbag structures are safer in earthquakes because they are not glued to each other - as bricks are?
A: Yes, that is certainly one of the reasons; another is that there is generally more resilience with the matrix of barbed wire and flexible fabric, and often even the fill can flex some within that matrix.
Q: I am moving ahead with using scoria in the north walls of my earth bag home. Just wanted to check in with you about Radon. Have you ever done a radon test in your home or know whether or not this is a potential issue?
A: Yes I did run radon test in my bedroom, since it is the smallest dome and is completely surrounded by bags of scoria, and a local person was telling people that scoria out-gassed radon. The result of this test was a very slight degree of radon, but not enough to be concerned about. I was relieved that this is obviously not a problem. But I would recommend putting a radon barrier under your floor, or mitigating for this potential, since this is a much more likely source of this.
Q: I hope to begin building our earth bag home early next year. It is going to be near a river, and with climate change, I am assuming that floods will happen. I am wondering if you have specific knowledge of an earth bag home built in a tropical area, that may have flooding. I have heard people say it is OK, others that their home "made it" through floods, but no real specific info.
A: I don't know of any specific cases of earthbag homes surviving floods, but it stands to reason that they would fare better than most homes, given that sandbags are used for flood control. Even if the walls don't collapse, a flood can cause a lot of damage to a home. I think you would want to try to keep water from entering the house no matter what. In order to do this, I suggest building on higher ground, and even elevating the living portion of the house higher than the surrounding terrain with a raised floor, either through interior fill or the use of raised foundation.
Q: I am considering doing a double wall of insulation, soil on the interior wall and volcanic rock on the exterior. I know this can add a great deal in terms of labor and expense, but my concern is that if I only do insulation, does this make the structure less flood resistant?
A: If you were able to source crushed lightweight volcanic stone in that region, this would be plenty flood resistant. Other lightweight fill materials, such as perlite or rice hulls, could present problems in flood conditions.
Q: I am concerned about flooding with a dome I am building. What is the best, safest solution for a stem wall or should I build directly on the floor?
A: If flooding is a major concern then it probably best to build the dome high enough that it is unlikely to be affected by flood water. This could mean building on some sort of stem wall or raised foundation that also allows you to raise the floor level inside the dome to avoid flooding.
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