Vapor Barrier Framing A Basement Wall Against Concrete

The vapour barrier is more properly called a vapour retarder.

Vapor barrier framing a basement wall against concrete.

Here are three different types explained. That is if the studs are going to touch the concrete wall. 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. Most jurisdictions require a 4 mil plastic sheet vapor barrier for basement walls against concrete.

Hence it must always be located on the warm in winter side of any insulation. The water vapor can come through the concrete from the soil or from indoor air that comes in contact with the concrete. 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. Or you can leave a 4 inch gap between the studs and concrete wall and probably get away with it.

Of foam against the wall this should not be a problem in your climate. 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. With fiber insulation and a vapor barrier moisture can get trapped in the insulation leading to moldy insulation and decay in the wood framing. So there is enough gap for air to flow.

The purpose of the vapor barrier is to stop the warm moist air from condensing on the cool concrete walls. This is accomplished by installing the vapor barrier to the warm room side of the insulation.