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Old 01-02-2011, 09:42 AM   #1
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raised slab foundation

I will be building a new house this summer. I will do some of it myself and sub out the rest. My whole life (59 years) everyone told me slab floor houses are cheap and not comfortable, so I have always stayed away from them. However I just started a business 5 years ago which took up all of my capital and I had move into one of those cheap slab floored houses. Now this house was not built correctly and the floor is cold and it is on ground level, but I never lived in a quieter house, as a matter of fact I never knew a house could be quiet, and the floor doesn't move when I walk across it. So now I want a slab in my new house, only raised 20 inches off the ground and warm. I tried to find information on a raised slab foundation and found nothing after considerable searching. Any time I mention I want a raised slab floor everyone tells me to do a crawl space. Sooo... I started thinking on how I would like to do this, and this is what I came up with. With new building products I think I can make it work. I will use ICF blocks on top of a footer, blue board under the slab along with foam and plywood on top of the slab to keep it warm and raise it off the ground. One of the major drawbacks I read about with slabs is the plumbing embedded in the slab making future repair difficult and undetected leaks causing damage. What I intend to do instead burying my water supply in the slab is to sink two inch PVC with two 45 degree angles in the slab placed strategically and then pull PEX tube through to supply the water. This way I avoid any connection/ joints between water manifold and faucets. This would also help detect leaks and allow repairs without tearing up slab. This plan would also do away with any void under my house ( like a crawl space, basement) so no mold, no need for drainage around my foundation. I know this is by no means standard but can anyone see an obvious flaw?? Thanks Tim


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Old 01-02-2011, 10:41 AM   #2
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I know this is by no means standard but can anyone see an obvious flaw??
Ayuh,... Your plan covers the supply lines, but what about the Waste lines,..??


Where is this gonna happen,..?? (Climate wise)


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Old 01-02-2011, 11:00 AM   #3
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Hi! I just spent all summer tearing out a wooden kitchen floor because of leak in icemaker. Your idea sounds good to me. Everytime I crawled in and out of that hole, I wished for slab.
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Old 01-02-2011, 02:17 PM   #4
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This is going to be in SD, very cold, we go 48 inch for frost. Is there a lot of problems with waste lines? Most of the horror stories I read are about pressure lines? Tim
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Old 01-02-2011, 04:38 PM   #5
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We've built foundations with slab-on-grade concrete floors in the past. Not that un-conventional here. They do take additional planning as you already realize. They also require extra attention to under slab vapor barrier & insulation, as well as frost wall insulation. The insulation requirements should be determined by the company that performs the homes heat calculations.

Something you may want to seriously consider is in-floor radiant heat, as it's the perfect situation to use it IMO.
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Old 01-02-2011, 08:27 PM   #6
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Yea, the in floor heat is something I'm considering. Anything different for the raised slab? Tim
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Old 01-07-2011, 08:10 AM   #7
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House slab on grade


We do house slabs on grade all the time. I live in Maine so we have very similar temps.

We just completed one a couple of weeks ago, the size was 80' x 34' with a couple of attached patios.

The slab was 6" thick with the edges thickened to 12". There was 2" of styrofoam under the slab, wire mesh on top of the styrofaom, radiant heat tubes tied to the wire mesh, and fibermesh in the concrete. We also had a double row of 1/2" rebar in the thickened edges.

After we strip the forms, we install 2" of styrofoam on the outside edges of the slab to hold in the heat from the radiant heating.

All the plumbing is in and under the slab. We've been doing slabs like this for over 20 years. I've never heard of anyone having any problems with their plumbing.

If the sub-base is prepared properly and you hire good subs, you should be just fine.



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