Vapor Barrier Above Concrete 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.

Vapor barrier above concrete slab.

Most exterior slabs do not need a vapor barrier. 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. Cure with waterproof sheets rather than with water or curing compounds. For a vapor barrier below a concrete floor slab most choose 6 to 10 mil polyethylene.

Some builders prefer to place the vapor barrier below the insulation or even below the gravel bed because they find. But consider going with a barrier that has water vapor permeance less than 0 3 perms. Vapor barriers come in two types 6 mil vapor barrier roll. If it doesn t a moisture imbalance could eventually cause a flooring failure.

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. One laboratory drying study indicated that 4 in. 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. However the vapor barrier under the slab must have a lower degree of permeance than the flooring or floor covering above the slab.

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. All vapor barriers should conform to astm e 1745. This guide says in section 2 4 1. Because extruded polystyrene insulating board will absorb little moisture the vapor barrier can be placed above or below the slab insulation.

If you are going to seal an exterior slab find a sealer that transmits water vapor breathes. If you want to make sure your slab on ground gets dry and stays dry use a vapor barrier. Concrete garage floors vapor transmission. 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.

The 2012 international residential code states. Choosing a vapor barrier. In general place the concrete slab directly on top of the vapor barrier with the subbase below. For some tips on this see sullivan s corner.