Vapor Barrier Above Concrete Slab

Is a vapor retarder barrier necessary for under the concrete slab of a garage or basement.

Vapor barrier above concrete slab.

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. Concrete garage floors vapor transmission. If you are going to seal an exterior slab find a sealer that transmits water vapor breathes. All vapor barriers should conform to astm e 1745.

For a vapor barrier below a concrete floor slab most choose 6 to 10 mil polyethylene. 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. Choosing a vapor barrier.

But consider going with a barrier that has water vapor permeance less than 0 3 perms. Cure with waterproof sheets rather than with water or curing compounds. 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 you want to make sure your slab on ground gets dry and stays dry use a vapor barrier.

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

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. The 2012 international residential code states. 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. Vapor barriers come in two types 6 mil vapor barrier roll.

This guide says in section 2 4 1. If it doesn t a moisture imbalance could eventually cause a flooring failure. Some builders prefer to place the vapor barrier below the insulation or even below the gravel bed because they find. For some tips on this see sullivan s corner.