Why Concrete Walls Need A Vapor Barrier For Moisture Protection | Basem*nt Masters Waterproofing (2024)

If you live in Warrenton, Bealeton, Marshall, VA, or any of the surrounding areas of northern Virginia, you may be familiar with a wet basem*nt. The addition of a vapor barrier for your crawlspace can save your home from crumbling from the ground up. Let’s dive into the ins and outs of vapor barriers to get a closer look at what is going on beneath the surface.

If a basem*nt wall system is designed and built to keep an interior space dry, then interior vapor barriers should be avoided regardless of where the insulation is located. If the basem*nt is not properly insulated, hot basem*nt air can seep into the foundation. For this reason, your basem*nt requires special insulation techniques. For example, in a basem*nt, if you have sheet pile insulation, you may need waterproofing. If you have foam insulation, you don’t need basem*nt waterproofing.

Preventing Moisture Build Up

Once the basem*nt is adequately waterproofed, insulation will help prevent condensation from forming. A moisture barrier in the basem*nt is a big advantage as it helps prevent moisture from entering the basem*nt at any time and causing unnecessary damage to the building. When building a new house or repairing a basem*nt, it is most effective to run a moisture barrier directly in the structure. It is best to place vapor barriers on foundation walls in basem*nts before installing posts and doing primary insulation. Installing a moisture barrier will help keep moisture in the basem*nt and prevent it from seeping into the walls and floors, leaving no room for mold.

Once groundwater is under control, proper use of basem*nt insulation, moisture barriers, and wall sealants can help keep your basem*nt dry and safe. You shouldn’t rely on an airtight basem*nt to protect against moisture. The reality is that moisture in one form or another will always be present in the basem*nt of a modern home. Water in the ground (no landscape can stop it all), condensation, dampness, even moisture from the stove or shower count! It’s a silly notion to deny that the water vapor that surrounds us all day will not make its way into our basem*nts.

Why You Need More Than Just Concrete For A Waterproofed Basem*nt

Water vapor can pass through the concrete from the subsurface or from indoor air that comes into contact with the concrete. Water vapor can condense if it passes through walls, ceilings or other obstructions and comes into contact with any surface or material below the dew point. A vapor barrier is a material used to prevent water vapor from penetrating a wall, ceiling, or floor during a cold winter. The intelligent vapor barrier adapts to wick moisture away from the wall, whether the humidity level is higher outside the wall (winter) or inside (summer). Drywall or green foil is not resistant to moisture trapped in the barrier.

Polyethylene plastic used in the basem*nt is often called waterproofing, but there is some controversy here. Water that forms on the polyethylene barrier penetrates the barrier and promotes mold growth. Moisture from the warm, moist outside air that fills the cavity in the wall begins to condense on the cool outer surface of the vapor barrier (assuming it is an insulating structure) and forms mold. This complies with regulations, allowing moisture that enters the walls to escape into the heated room. This can cause condensation to form in the cavity walls, which can damage the building material and cause mold to grow.

If the basem*nt walls are insulated from the outside, a vapor barrier is not required. Otherwise, it can be dangerous as it can trap moisture in moisture-vulnerable areas. However, the focus here is on how moisture, in the form of water vapor, leaves the foundation walls and migrates into the basem*nt or outside above ground level. The water vapor inside will then condense on the inside surfaces of the foundation walls, providing moisture for mold growth and other problems.

The Use of Polyurethane Sheeting As A Vapor Barrier

Regardless of various conditions, an identifiable common problem is that moisture tends to condense on concrete walls. First, you need to imagine a concrete (or block) wall as a giant sponge that absorbs moisture (water vapor). Moisture in your home or basem*nt can cause some form of wobble, which you will need to correct by using a damp barrier made from moisture-resistant material. Polyurethane sheeting is the best and most common form of waterproofing that most people use to prevent moisture from entering their homes through basem*nt walls. Not to be confused with a vapor barrier, which is located on the warm side of the wall in front of the insulation and behind the drywall.

The vapor barrier goes into the basem*nt wall, behind the insulation and the frame. The purpose of the waterproofing layer is to remove moisture from the walls to protect the insulation. If you have installed insulation in your basem*nt, there are three types of waterproofing you can use to keep the space dry. Historically, layers of drainage, waterproofing, and vapor barriers have been laid outside the perimeter of basem*nt walls, overlying rubble layers, and under concrete slabs. The principle of operation was to prevent liquids, steam, and capillary water from entering the structure.

The Role of Proper Ventilation and Dehumidifiers

Moisture barriers can dry out in the basem*nt, an area where moisture can be removed through ventilation or dehumidification. It is recommended to avoid rigid foam or spray foam systems as they allow drying, are less susceptible to moisture damage and do not promote mold growth. These are important characteristics of materials that come in contact with basem*nt walls and basem*nt floors. Building walls with studs, insulating the resulting cavities, and covering the interior with a plastic moisture barrier is a common mistake that often leads to odor, mold, rot, and corrosion problems! If you’re placing a polyethylene vapor barrier behind a drywall-covered drywall-framed wall, it may be time to seek the help of a local professional waterproofing expert.