Alternative To Portland Cement Concrete for Basement Slab on Rock
I’m building a garage apartment with a basement in Dallas, and the basement will be cut into limestone, which starts at about 4-5′ deep. At the full cut depth of over 9′, the limestone is competent. Lateral restraint at the base of the walls can be provided by simply keying the footing into the limestone, so a conventional concrete slab isn’t required.
Ground temperatures at that depth are almost constant at about 70 degrees, so the floor does not need to be insulated. All that is required is drainage to a sump pump, a vapor barrier, and a leveling layer.
Would a self-leveling gypcrete floor on a compacted sand base be a fast and greener alternative to the usual concrete slab?
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Replies
I would use 1/2"-3/4" river rock as a capillary break, not sand, at least 4” thick to cover a perimeter socked draintile to a sump. Then I would cover the rock with a taped and sealed 20 mil WRB. Using a double layer of Gyp-Crete or CDX plywood floor underlayment would be a good option, over 12” strips of 3/4" CDX “rainscreen” to create a ventilated channel.
Make sure as you plan all this work, you get a soils test done, as you know, here in North Texas, the soil movement can be quite high.