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Proper way to pour a basement slab?

Posted by mebke33 (My Page) on
Tue, Aug 28, 12 at 17:23

I also posted this on the "building a home" page. 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?

Depends on the weight bearing ability of the soil under the footers and slab.

RE: Proper way to pour a basement slab?

For pouring the basement floor, one must take care to prevent future cracking. Unlike pouring an open slab of concrete, the basement floor has the unique aspect of sitting within vertical concrete walls so some special techniques are taken to smooth the concrete from only one side.

RE: Proper way to pour a basement slab?

compacted sand or gravel to be brought up to the level of the footing, then 10 mil vapour barrier/poly to cover entire floor area from wall to wall with all cuts or holes in the poly sealed.
Pour slab 4" thick on top of the footings. THis is the standard procedure and widely accepted as the proper way to lay concrete. The only guarantee with concrete is that it will turn gray and crack. you can try to cut in control joints but sometimes the floor doesns crack where you want it to anyway.


RE: Proper way to pour a basement slab?

Our full size basement has a concrete floor poured, with steel footings that hold the 2000 sq ft rancher house. All footings have contact with concrete but you can see that the floor was poured first - while footings had collars around them. Then the footings got the concrete too. So there is a circle line in the concrete around the footings. This is a 5 year old and no new cracks anywhere. I hope this makes sense, unless I can find pictures.

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