Vapor Barrier Above Concrete Slab

Because extruded polystyrene insulating board will absorb little moisture the vapor barrier can be placed above or below the slab insulation.

Vapor barrier above concrete slab.

In general place the concrete slab directly on top of the vapor barrier with the subbase below. 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. For some tips on this see sullivan s corner. All vapor barriers should conform to astm e 1745.

Choosing a vapor barrier. If you are going to seal an exterior slab find a sealer that transmits water vapor breathes. Our moistureblock is a 6 mil polyethylene film vapor barrier that is used during the installation process with floating laminate luxury vinyl planks and engineered wood floors. However the vapor barrier under the slab must have a lower degree of permeance than the flooring or floor covering above the slab.

Concrete garage floors vapor transmission. 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. 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. 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.

This guide says in section 2 4 1. Some builders prefer to place the vapor barrier below the insulation or even below the gravel bed because they find. For a vapor barrier below a concrete floor slab most choose 6 to 10 mil polyethylene. Vapor barriers come in two types 6 mil vapor barrier roll.

Cure with waterproof sheets rather than with water or curing compounds. One laboratory drying study indicated that 4 in. But consider going with a barrier that has water vapor permeance less than 0 3 perms. The 2012 international residential code states.

Most exterior slabs do not need a vapor barrier. 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. 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. If it doesn t a moisture imbalance could eventually cause a flooring failure.