+- Punaweb Forum (http://punaweb.org/forum)
+-- Forum: Punaweb Forums (http://punaweb.org/forum/forumdisplay.php?fid=3)
+--- Forum: Building in Puna (http://punaweb.org/forum/forumdisplay.php?fid=12)
+--- Thread: Cob building (/showthread.php?tid=12678)
RE: Cob building - unknownjulie - 11-12-2013
When I did the math regarding using earthbags with cement added here, it got real expensive real fast. It's the cement and the logistics of trying to haul it all back to the lot and then what about power? And are you going to hand mix all of it? etc.
RE: Cob building - MarkP - 11-12-2013
I have thought about this alot and I keep coming back to simply using the cement as economically as possible. Basically build a ferro-cement house. Other variations on the same theme would be ICFs and cast in place concrete. The concrete mix would be carefully designed as commercial concrete is these days. Cinders for filler would not be included. For living structures stone would not be included. For walls that people don't spend a significant amount of time standing under or within reach of, un-reinforced stone would be acceptable since if it falls down no one gets killed and you can re-build at your leisure. Commercially prepared blocks and cement board products would be desirable because of the high quality control compared to DIY efforts. That brings us right back to how things are usually done today. In other words there ain't no free lunch out there waiting to be taken advantage of but strangely not discovered yet.
CMU block walls full of re-bar and concrete, then back-filled on the outside with cinders, gravel, or whatever gave the best bang for the buck, would in my opinion get you the same results as an earth-ship but without the uphill battle to get it permitted and without the backbreaking labor.
RE: Cob building - Rob Tucker - 11-12-2013
One practical alternative is to use an ICF system for the concrete work. There is an excellent ICF (insulated concrete form) block called Apex which is carried by Lowe's. Apex will reduce your concrete volume to 26% and still give you the full strength of a full wall. Best part is it is insulated at R-30, is six hour fire rated and does not require a mason's skills or much skill at all. You can face it with a thin veneer of lava if you want to.
My own home is built with this method.
RE: Cob building - Kaixin - 11-12-2013
aramis,
I have been playing with the soils and other materials to see what can be used for wall building. The soil I have in mountain vw is not 'clay' like adobe but its a thick enough muck to make not cob, but mud walls. They are more erosive but you might find a way to tame it with some experimentation or mixes. You can find dry hills of almost pure clay down south, saddle rd and other areas but i havent spotted many around puna.
some prefer concrete but i find it cold and unpleasant to live inside, and it does not breathe well in this moist environment especially together with any timber causing rot and collected moisture. An alternative to cob or concrete but still very natural is lime plaster. You can buy 50-100lb bags of hydrated type s lime in garden stores in hilo etc. Lime plaster and mortar have been used for hundreds of years in moister climates like Ireland for the very reason its a breathable material and can transport moisture out like clay plasters. they even used it on the old churches around here, but they harvested the coral back then to crush it into lime powder and coral harvesting is illegal anymore so..
anyway you may want to look into it. the lime mortar recipe is general 1 part putty (lime mixed with water) to 3 parts sand, but you can use any gritty slow degrading material like silt or crushed cinder, etc. You can add fiber (dried grass, coconut husk, your dogs hair..) to make plaster for walls, floors, and so on.
RE: Cob building - aramis720 - 11-12-2013
Great, thanks everyone for this great information. I'm still probably a year out from construction so I'll follow up a bit closer to go time. Good to hear that there are some options using local and natural materials even if traditional cob sounds like it's not really an option.
RE: Cob building - aramis720 - 11-12-2013
Kaixin, do you have any pics you can share of your creations? Curious what is doable with Mountain View soil since I'm looking to buy in Fern Acres.
RE: Cob building - aramis720 - 11-12-2013
Rob, do you have any pics you can share of your home? And what did it cost per square foot to build this way?
RE: Cob building - Rob Tucker - 11-12-2013
I have too many pictures. My costs, doing it 95% myself, ran about $65 psf.
RE: Cob building - Kaixin - 11-12-2013
afraid i havent started on the walls yet im still under construction on the timber frame (ohia) as you see in this photo but i will put some photos of the walls once theyre in.
http://img.photobucket.com/albums/v238/FlappingLlama/Shared/frame.jpg
however, the person i learned it from helped build this house here using lime plaster and timber frame if youd like to see it on a completed structure - http://simondale.net/undercroft.htm
RE: Cob building - oink - 11-12-2013
Kaixin, how long did it take you to get permits?
Pua`a
S. FL
Big Islander to be.