Moisture Barrier Against Concrete Wall

Below grade walls and floor slabs transmit ground moisture through concrete walls or slabs.

Moisture barrier against concrete wall.

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. 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. 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 smart vapor retarder is able to adapt its permeability to allow the wall to dry should moisture get trapped in the wall cavity.

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. The water vapor can come through the concrete from the soil or from indoor air that comes in contact with the concrete. So there is enough gap for air to flow. A vapor barrier reduces the movement of water vapor by diffusion.

Of foam against the wall this should not be a problem in your climate. In any case the vapor barrier must point to the warm side. This is a water infiltration barrier and perhaps an air barrier. Actually a concrete wall or a masonry wall without cracks is in itself a very good air barrier.

Or you can leave a 4 inch gap between the studs and concrete wall and probably get away with it. Most jurisdictions require a 4 mil plastic sheet vapor barrier for basement walls against concrete. If you have a double brick wall in the above ground portion of the house we will often find some kind of building paper against the brick inside the house. That is if the studs are going to touch the concrete wall.

A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. Moisture barrier between the sole plate the concrete slab. 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. Crawl spaces benefit from a polyethylene moisture barrier placed directly over the exposed earth.

Sole plates or sill plates are the first pieces of framing lumber placed in home construction. This material adapts to let moisture out of the wall whether. This will give you two vapor barriers one before and one after the stud wall framing. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.