Inexpensive barn/garage using concrete with styrofoam aggregate

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Hi all, I've got another question that I need a bit of help with, what is the right mix ratio and thicknesses for footings and walls for concrete that has expanded styrofoam pellets mixed in. Now that I've gotten the house almost completely built I need to start building my barn/garage/workshop. Since building the house sucked up almost every last penny I had in savings I need to build my 1 and a half story barn CHEAP. I think the best option I have for cost, insulation, seismic resistance and do-it-myselfability is concrete that has styrofoam beads (like you find in a bean bag chair) mixed in with it. According to the research that I've done the styrofoam allows the concrete to expand/contract and flex a little without cracking. Im going to pour it into a slip form mold made out of two 4x8 sheets of plywood and some scrap 2x4s. This way I can do just one section of the walls at a time by clamping the open side of the form to the previous section and pouring more concrete. I should be able to do this pretty easily and just buy more concrete and mix to do another segment when I have the cash, its going to take a while, but at least its doable (I think). It wont be as pretty as the house, but I can stucco over the concrete and make it look decent. The roof frame is going to be timber from wood chainsaw milled here on my land with the roof itself aluminum and (eventually) polyurethane sprayed on the underside for rigidity and insulation.

I dont have any idea what the proper mixture is though and how thick the walls should be to support the upper story and roof, if you all have any ideas I'd really appreciate your thoughts on whether this is workable or just another idea of mine that sounds clever but doesnt actually work.... Thanks Dave

-- Dave (AK) (transmach@hotmail.com), May 04, 2000

Answers

It sounds really great! There is all sorts of information available about peat crete and paper crete and straw crete and fibre crete. the latest TMEN has a good article about paper crete.

I am looking to build the least expensive home possible that the building inspectors will pass and a lender will finance. So far I have only heard sneers on some of the concrete admixed with other items. A block layer told me he can put me up a building for $6 a square foot, and $7 for the structural beams. I put a post up about concrete block house and some very good suggestions were posted here, my favorite one being by the folks who makde their building like a thermos bottle!

-- Elizabeth Petofi (tengri@cstone.net), May 04, 2000.


My question is, if a batch of concrete has time to set up before the next pour, will the finished structure be sound? I would really like to know the answer to this one, as it may help us, too.

-- Kathleen Sanderson (stonycft@worldpath.net), May 04, 2000.

Dave: Sounds fun!! I built a rock and concrete cabin with walls 12 inches thick. My footing is 24 inches wide by 24 inches deep. You may need it a lot deeper depending where you live. I just did a slip form wall technique about how you described. I don't have any experience with the strofoam but I believe to keep adding on you have to use re- bar. Why not use re-bar and forget the foam? I've got some pictures on a web site if you want to peek and i'll be glad to give tips on slipform if you would like. ...Kirk

-- Kirk Davis (kirkay@yahoo.com), May 04, 2000.

This is all theory - not experience. Hope it triggers some useful thoughts.

I've heard of people using a mix of concrete and sawdust - cheap if the sawdust is cheap, fair insulation, and relatively light. Don't remember the proportions, but I do remember there was surprisingly little cement. Has obvious weaknesses if you've got termite worries. Good as an infill panel, harder to predict if you want load-bearing walls.

If you're casting panels in-situ, you can put a slab of well-greased timber up the centre of one edge, then pull it out when your panel is set, and cast the next panel: you're doing your own tongue-and-groove panelling on a LARGE scale.

I've heard of people doing the slab floor, laying plastic sheet on it, and then pouring and setting wall slabs in a form on that. When they're set, they stand them up. I believe they use it for commercial buildings and load-bearing walls - I wouldn't have the confidence (or the heavy-duty machinery) to do that, but lightweight infill wall panels might be OK.

Looking back at this, my prejudices are showing. It's all infill, because that's what I've decided on - I will put up an open-sided hay- shed, then fill in the walls, working out of the weather like a gentleman.

-- Don Armstrong (darmst@yahoo.com.au), May 05, 2000.


Dave, I'm a bit skeptical on this, though I'd love to be proved wrong. I've done quite a bit of building, and it seems to me that if you put enough styrofoam into the concrete to give it a decent R value, it wouldn't have much strength. I'd recommend using regular aggregate instead of the foam, then insulate it outside the wall, or inside the wall. If you insist on using foam pellets, which sounds fine for R value, pour a double wall, with maybe six inches of foam in the middle.

I can't speak for your vicinity, but here the aggregate costs $15 per cubic yard, and cement costs $7 peer cubic FOOT, so the aggregate is really not that much of a consideration. And the aggregate I'm talking about is sized correctly for using in concrete. What are you going to do with the pellets? If you fill in between them with neat cement, you'll probably be paying more than you would have for real concrete.

Let us know if you actually are able to do this, please. And do you have any data on how much R value you could expect from this type of wall?

JOJ

-- jumpoff joe (jumpoff@echoweb.net), May 05, 2000.



Long ago in the dim past TMEN had some articles about Andy Davis and his Cave Homes. Do you remember? His first one was octagonal. He had a system where he had a sand base, poured his wall on the sand and then tilted it up (I think he had a crane) and he had "ties" which were in the concrete walls which he fastened to each other.

There is a book for sale on the Davis Caves. Andy died but his son took over the business and has a web site. There were at the Energy Fair. Doing inground homes now. some interesting photos of the pours etc. But they are not telling their secrets of how they do it any more so we can steal the ideas and do our own!!!! Pity.

-- Elizabeth Petofi (tengri@cstone.net), May 05, 2000.


The addition of styrofoam to the concrete mix won't work. You'll never get a consistent distribution of the styrofoam as the styrofoam will float to the top and resists coating.

There is a company... I believe their product is called RASTRA block... that has solved this problem with a foam pre-treatment so the concrete will coat the surface of the foam. They only sell the finished block though...

-- Steve (OR) (senna12625@hotmail.com), June 15, 2000.


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