This is in response to a letter from B.V. (posted 1/12/06) on Insulated Concrete Forms (ICFs) and http://www.polysteel.com. As I said in my 1/7/05 letter, the major shortfall of this type of construction is the roof. Otherwise, this a good idea, in particular to insulate the concrete wall from the elements so it acts as helpful thermal mass for heating and cooling efficiency. Also, reinforced poured concrete is far superior to block, just try drilling through each sometime. There are several companies that make these systems. I happen like the hanger system (for joists and trusses, etc.), and the system of attachment for drywall and exterior siding of Nudra: http://www.nudura.com Still, building a home or retreat this way still begs the question: Why invest in walls that can sustain a hurricane or tornado and then put on a conventional roof that can’t? My personal favorite solution to this problem is using a span-crete (pre-cast steel reinforced concrete) to do the roof span, and then insulate over it with hard foam, then put down a 60 mil rubber roof membrane, and then two feet of topsoil, netted to hold it, and slightly pitched to drain. For added protection and strength, pour a slab over the roof membrane of at least four inches, and put the soil over that. [JWR Adds: Be sure to consult with an architectural engineer to make sure that all of this is done safely. Loads must be properly supported. “Dead” loads can be deadly! Just ask Ken Kern–the alternative housing author who died in the collapse of a rammed earth dome that was under construction.]
Here in the North, where we need to go down four feet to get the foundation well below the frost line and thus have basements (might as well go a little further). The temptation is thus to them make an earth shelter or underground home this way, basement and main floor both buried. The problem is the inward pressure on the flat vertical concrete walls it too great. While such pressure is not large a factor on an 8 or 9 foot poured concrete basement wall, is certainly is for a 16 or 18 foot wall. My solution, and compromise, is to bury and berm just 10 to 12 feet of the wall (10 inches think) thus berming the first floor of the house (above the basement) half way up to the lower ledge of the windows. The space between the top of the berm and the roof line is then conventionally insulted and sided (consider fire resistant materials such as brick, stone, fiberboard, stucco, Masonite, steel, stainless steel… http://architecture.about.com/od/buildyourhous1/tp/siding.htm ). Your options for the roof are to wall it off and use it as a patio, or for max insulation put some topsoil there as I said before. You can put on gutters or some sort of little awning over the windows and doors at least to handle channeling the run off. Snow load isn’t even a factor with how strong this roof is, nor is the concern of volcanic or other fall-out that, particularly if it gets wet, will collapse most conventional roofs. Small and simple rectangular ranch home designs work well, but to really maximize the space I like having a split level with partial exposure to the basement/lower level for two bedrooms below and one bed above on a 28’ by 36’ footprint, or similar size. The exterior door is then above the berm height, as well. This design will give your home or retreat an amazingly strong design and a reasonably conventional look to it. Note you can attach a hardened garage on to this, and even put a “stealth retreat” under the garage. Sound familiar? [See the SurvivalBlog Archives.] – Rourke http://groups.yahoo.com/group/survivalretreat