Vapor Barrier Above Concrete Slab

In general place the concrete slab directly on top of the vapor barrier with the subbase below.

Vapor barrier above concrete slab.

The rate that moisture escapes from a slab depends on the concrete w c the density of the finish the ambient conditions above the slab and the moisture below the slab. Vapor barriers come in two types 6 mil vapor barrier roll. If you want to make sure your slab on ground gets dry and stays dry use a vapor barrier. Is a vapor retarder barrier necessary for under the concrete slab of a garage or basement.

New generation vapor barriers made from the highest grade virgin polyolefin resins have been developed that are considered true below slab vapor barriers or concrete vapor blockers. If it doesn t a moisture imbalance could eventually cause a flooring failure. For some tips on this see sullivan s corner. Aci 302 1r 11 guide for concrete floor and slab construction doesn t advocate universal use of vapor barriers but does make recommendations for their proper use.

This guide says in section 2 4 1. However the vapor barrier under the slab must have a lower degree of permeance than the flooring or floor covering above the slab. Most exterior slabs do not need a vapor barrier. Thick concrete samples having a w c 0 50 and sealed from below required 82 days for the vapor emission rate to reach 3 0.

All vapor barriers should conform to astm e 1745. We find ourselves having to explain that the vapor retarder wasn t required or necessary for a concrete garage floor poured at or above grade. For a vapor barrier below a concrete floor slab most choose 6 to 10 mil polyethylene. It is also possible that too much water or cement paste would be absorbed from the concrete by the sand but probably not under most circumstances.

These 10 mil and 15 mil vapor barriers are very puncture resistant and will not break down over time creating a true moisture barrier between the sub grade and. The 2012 international residential code states. Cure with waterproof sheets rather than with water or curing compounds. Choosing a vapor barrier.

But consider going with a barrier that has water vapor permeance less than 0 3 perms. Some builders prefer to place the vapor barrier below the insulation or even below the gravel bed because they find. One laboratory drying study indicated that 4 in. Because extruded polystyrene insulating board will absorb little moisture the vapor barrier can be placed above or below the slab insulation.