Should vapor barrier in slab be under 4 in. of gravel or on top of gravel?
1) I’m building a 2-car garage with upstairs apartment in zone 4, 26′ x 28′. getting different opinions on whether the vapor barrier -6ml plastic- should be under the 4” of gravel or on top of the gravel directly under slab? Some are saying it is not good to pour concrete right on plastic, although this seems to be the most common way to do it. any input would be appreciated. carl
2) I’m putting in radon mitigation in slab — 3 in. PVC — will this make a difference where plastic should be?
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