Moisture Barrier Against Concrete Wall

So there is enough gap for air to flow.

Moisture barrier against concrete wall.

Crawl spaces benefit from a polyethylene moisture barrier placed directly over the exposed earth. Most jurisdictions require a 4 mil plastic sheet vapor barrier for basement walls against concrete. Not to be confused with a vapor barrier which is placed on the warm side of the wall just in front of the insulation and behind the drywall a moisture barrier goes against the basement wall. Or you can leave a 4 inch gap between the studs and concrete wall and probably get away with it.

This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. The water vapor can come through the concrete from the soil or from indoor air that comes in contact with the concrete. A smart vapor retarder is a vapor retarder material with the unique ability to react to changes in relative humidity by altering its physical structure. That is if the studs are going to touch the concrete wall.

This will give you two vapor barriers one before and one after the stud wall framing. This is a water infiltration barrier and perhaps an air barrier. These plates must be made of pressure. When a vapor barrier is on the side of a wall where the dry air is i e outside in winter or inside in summer moisture problems can occur.

A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. In any case the vapor barrier must point to the warm side. A vapor barrier reduces the movement of water vapor by diffusion. A smart vapor retarder is able to adapt its permeability to allow the wall to dry should moisture get trapped in the wall cavity.

Sole plates or sill plates are the first pieces of framing lumber placed in home construction. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Holes in the vapor barrier that allow humid air through may allow a lot more water vapor into an assembly than the vapor barrier is stopping. Of foam against the wall this should not be a problem in your climate.

Below grade walls and floor slabs transmit ground moisture through concrete walls or slabs. The other option is to set the 2 4 wall framing in 4 from the masonry or concrete basement walls and use just the vapor barrier on the insulation facing toward the living space. Moisture barrier between the sole plate the concrete slab. With fiber insulation and a vapor barrier moisture can get trapped in the insulation leading to moldy insulation and decay in the wood framing.