In an exterior wall, brick on the outside, sheetrock on the inside, and insulation in between, where should the vapor barrier be placed?

In an exterior wall, brick on the outside, sheetrock on the inside, and insulation in between, where should the vapor barrier be placed?

• A. behind the sheetrock
• B. Spray on barrier behind the brick
• C. behind the brick
• D. top half of the wall only

Answer: (A)

Moisture control in wall assemblies relies on placing a vapor barrier on the warm side of the insulation to slow diffusion of interior moisture into the cooler wall cavity where it could condense. In this wall, the interior is the warm side, so the vapor barrier should be installed behind the sheetrock, between the interior space and the wall cavity. This blocks moist indoor air from entering the insulation and brick veneer, reducing condensation and mold risk. Placing the barrier behind the brick would put it on the exterior side and allow interior moisture to reach the cavity, which is undesirable. A barrier only on the top half or a spray-on barrier behind the brick would not provide continuous protection across the whole wall.

Moisture control in wall assemblies relies on placing a vapor barrier on the warm side of the insulation to slow diffusion of interior moisture into the cooler wall cavity where it could condense. In this wall, the interior is the warm side, so the vapor barrier should be installed behind the sheetrock, between the interior space and the wall cavity. This blocks moist indoor air from entering the insulation and brick veneer, reducing condensation and mold risk. Placing the barrier behind the brick would put it on the exterior side and allow interior moisture to reach the cavity, which is undesirable. A barrier only on the top half or a spray-on barrier behind the brick would not provide continuous protection across the whole wall.