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Dodger
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# Posted: 20 Sep 2012 11:42am
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I am building a small cabin, 20x24, and this will be my first cabin build. Doing a lot of research and have been glued to this site. Foundation and roof are the only areas that I am still unsure of. Wanting to build on 16"x8"x8" concrete blocks piers. I will go down to frost depth for my footer. Question is, if I build my piers from blocks, can I just use a single layer, or should I double up my blocks? I will need 5 blocks stacked from my footer, so can I just use the single layer, or should I use 10 blocks per pier.? Piers will be 6' apart, and three rows, center row will be at 10', so 15 total. Does that make sense? Going to triple 2x12s for my beams. Second question is, do I have to set rebar and fill blocks with concrete, or will the blocks alone be stong enough? Was going to fill the top blocks regardless, to hold my hardware. Will this work? Should I just plan on filling my blocks with rebar and concrete? Doing a simple green cabin with mostly recycled materials, this will be a family project. Any help would be great.
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MtnDon
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# Posted: 20 Sep 2012 12:55pm
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Questions;
What's the soil like?
What's the depth of water table? Should be deeper than the frost depth hopefully.
Does the ground get soaked with water at any time of year?
one story, loft, 2 story???
What's the snow load???
Concrete blocks can work for piers but they should have rebar from footing to the top and be filled with concrete. 8x8x16 in pairs bottom to top, alternating direction in ascending layers is better than a single column. Footer at least 16x16 x 8 thick, Rebar in footer in X or # shape, Rebar should be encased completely in concrete, none sticking into the dirt.
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GomerPile
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# Posted: 20 Sep 2012 01:54pm - Edited by: GomerPile
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Using blocks for piers is a pain in the ass. You need to get them all at EXACTLY the same elevation which can be really tough. The use of leveling hardware makes it less critical but is costly.
Technically (according the the IRC) you need to install a concrete footing larger than your piers. That means you need to pour the footing in each hole to the exact same elevation so that the blocks you stack on it are the same height.
You could say "screw the footings" because you have rocky soil. Then you need to make each pier hole the exact same depth so all the piers line up. You end packing soil in the hole, stack the blocks, measure and do it all over again until you want to kill yourself.
Better Idea: Buy bags of cement, cardboard tubes, and rebar.
1) Pour footings in each hole
2) stick some lengths of 1/2 inch rebar in there for support.
3) when the footings cure install the cardboard tubes and backfill (forget about the elevation for this step)
4) Using a laser or liquid level mark each tube to the same elevation and cut with a sharp knife
5) Fill with cement.
Tip: break up concrete blocks and use the pieces as fill. Don't get stupid with it, but in a 12 x 48 inch tube I think you can get away with using a block or two for fill. If this is a critical application then don't do this.
Tip: If your tubes will be in the ground empty for any length of time wrap them with plastic and install plastic over the top until you are ready to pour. They get soggy when wet.
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toyota_mdt_tech
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# Posted: 20 Sep 2012 02:44pm - Edited by: toyota_mdt_tech
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Quoting: MtnDon Questions; What's the soil like? What's the depth of water table? Should be deeper than the frost depth hopefully. Does the ground get soaked with water at any time of year? one story, loft, 2 story??? What's the snow load??? Concrete blocks can work for piers but they should have rebar from footing to the top and be filled with concrete. 8x8x16 in pairs bottom to top, alternating direction in ascending layers is better than a single column. Footer at least 16x16 x 8 thick, Rebar in footer in X or # shape, Rebar should be encased completely in concrete, none sticking into the dirt.
What Don said. Especially on the double brick columns, rebarred, filled with concrete.
But I'm with Gomer, use the sono tubes.
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MtnDon
Member
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# Posted: 20 Sep 2012 09:51pm
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Sonotubes work very well with Bigfoot Footing Systems; the larger the diamter tubes, the better. Not for the ability to support more vertical load but because larger diameter columns resist lateral movement better.
And hopefully you have none of the negative things with your soil.
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