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The Work of Art and The Art of Work Kiko Denzer on Art |
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[Cob] continuous foundation reinforcementAmanda Peck ap615 at hotmail.comMon Jan 3 18:41:16 CST 2005
I like the idea of a Frank Lloyd Wright style rubble trench foundation (or, slightly different, a Frost Protected Shallow Foundation often mentioned on the same sites) with a drain to daylight in the bottom and a bond beam (and/or block, or stone, or urbanite on top). It would be more work for you (think pounding the gravel into the ground until it rings!) than if you had someone else come in and pour the concrete, BUT.... The reason would be that your wall is going to be pretty thick, and your foundation needs to be right at that same thickness. You need to have something other than cob up for a stem wall--6-12 inches above ground. Putting all of that in concrete might well be a LOT of concrete. I also think I would not use any rusty barbed wire that you had hanging around, if that's what you meant by "local." It would probably just continue to rust until there was only a brown hole left. What they sell around here is really rusty looking rebar or that heavy welded wire fence stuff, also looking very rusty. I've been dubious about that stuff too, for the same reason. But rebar is a lot thicker and presumably stronger than even new barbed wire. (I'm prejudiced here. Maybe unnecesarily. Years ago a major freeway bridge in Nashville failed, although not catastrophically, because of rusty rebar. Winter salt on the concrete bridge combined with some inevitable cracks and fifteen years or so later there were some goodsized holes looking down many feet to the river--the salt, of course, played a major role in this. Rebar may work perfectly nicely in a stemwall or foundation, but I think I'd ask someone. Of course while a building is subject to earthquakes, it doesn't get the continuous rumbling that a very very busy highway bridge gets.) Here's a kind of random link for the frost-protected shallow foundation--from the Home Builder's Association. I haven't posted this link in a couple of months. The .pdf file of designing earthen buildings for--not just--earthquake country by the man, Gernot Minke, whose house was in a natural building magazine a few months back. Unfortunately, his house isn't in this link, and it doesn't come up in the first page with a search. I think he really does have earthen sinks (with or without some concrete). www2.gtz.de/Basin/publications/books/ManualMinke.pdf By the way those of us who DON'T live in earthquake country shouldn't get too cocky. In Sarah Andrews' mystery Fault Line, her detective asserts that a small earthquake that would hardly be worth reporting in earthquake country could be totally devastating in, say, Boston--and shape of the sand is a big reason. The book may tell you more than you ever wanted to know about earthquakes and buildings, but it's set in a mystery story (not necessarily recommending the 500-pound gorilla of book sales to purchase a fairly recent paperback, but its an easy way for all of us to see the cover): http://www.amazon.com/exec/obidos/tg/detail/-/0312984456/ref=pd_sim_b_6/102-7887725-1522507?%5Fencoding=UTF8&v=glance ....... Susan wrote: I am about to get started on an approximately 11-foot diameter circular cob building - off-grid and under 120 interior square feet (no permit necessary.) I plan to dig a footing trench, fill it with concrete to grade level, and build a stone stemwall above that. I'm building in earthquake country- the southernmost Sierra foothills at 3,500 ft elevation. I'd like to use as much on-site material as possible, but part of me also wants to make it as solid as possible and document the process for future interactions with building officials. My question is: What do you think of using barbed wire as reinforcement in the concrete instead of rebar? Any ideas?
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