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Proper way to pour a basement slab?

Posted by mebke33 (My Page) on
Tue, Aug 28, 12 at 15:49

We are trying to decide on a sub for flatwork in our ranch style home with a walk-out basement. We have several differing opinions on how the the basement slab should be poured. One states that the slab should be in direct contact with the footings. The second states that the slab should float on a bed of gravel and not directly contact the footings. Is there a standard technique or is this just individual preference? Does anyone have any experiences, either good or bad, for either technique? Thanks.

Follow-Up Postings:

RE: Proper way to pour a basement slab?

my answer? it sort of depends on your climate. If you are at all in a heating climate, I would say both are not ideal. Incorrect? not really, just not ideal. However of the 2 options, I would side more with the gravel then the contact with the footer as it helps to give you a capillary break. If you are in a heating climate, there should be 1.5-2" of foam under the slab, and preferrably between the slab and the footer for a thermal break.

RE: Proper way to pour a basement slab?

I'd say that a lot depends on the extent to which you have a water and saturated soils issue. Theoretically, if no water can get past the foundation walls the slab will never have any movement.

On the other hand if water gets under the slab it's going to move with the expansion and contraction of the soil when it is wet and dry.

Whatever you decide, be sure you have good drainage away from the foundations and basement slab. If moisture is an issue in your area, include a sump drain and pump. This will require a slotted space between foundation walls and floor slab.

The other comments about temperature are also important to consider.

Good luck1

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