I suspect the reason for not using visqueen is to reduce the potential for
curling due to differential shrinkage rates. In a hot climate, you will lose
moisture on the top of the slab at a fairly high rate compared to the bottom
anyway, but visqueen would aggravate the problem.
I use visqueen fairly often under large grade slabs in the Pacific Northwest
but would never rely on it as an effective vapor barrier. I just use it to
reduce friction between the concrete and the base material so there's less
developable drag force and shrinkage cracking in the slab. I usually have
the contractor puncture it so bleed water can't build up on the underside of
the fresh concrete. Seems to work pretty well.
From: George Richards, P.E. [mailto:george(--nospam--at)BORM.com]
Sent: Monday, January 17, 2000 10:39 AM
Subject: Visqueen under slab in Arizona
We are being told that it construction practice in Arizona along the
Colorado river is to not place Visqueen under residential floor slabs.
Would anyone please comment.
George Richards, P. E.