Vapor Barrier Framing A Basement Wall Against Concrete

With fiber insulation and a vapor barrier moisture can get trapped in the insulation leading to moldy insulation and decay in the wood framing.

Vapor barrier framing a basement wall against concrete.

Before framing the walls of your basement install a moisture barrier to prevent water and moisture from entering the wall cavity. It is designed to stop moisture in the form of vapour that is inside the house from moving into the walls and forming condensation or ice. Usually that is right behind the drywall. Without a vapor barrier water vapor flows through the insulation and if the concrete wall is cold enough the water vapor condenses on the concrete and drips down the wall.

Most jurisdictions require a 4 mil plastic sheet vapor barrier for basement walls against concrete. The vapour barrier is more properly called a vapour retarder. Here are three different types explained. Hence it must always be located on the warm in winter side of any insulation.

The purpose of the vapor barrier is to stop the warm moist air from condensing on the cool concrete walls. Or you can leave a 4 inch gap between the studs and concrete wall and probably get away with it. You should then use fiberglass insulation that has a vapor barrier between the studs with the vapor barrier facing in toward the living space. Building codes usually require a vapor barrier 4 mil plastic sheeting on exterior basement walls if the framing is attached to masonry or concrete surfaces or if the wood framing butts up against the outer basement walls.

Of foam against the wall this should not be a problem in your climate. That is if the studs are going to touch the concrete wall.