Moisture Barriers For Basement Walls

Exterior waterproofing may not be suitable when there are external obstructions that make it too difficult or expensive to access the foundation, or when space constraints impede the excavation process. In such cases, an Interior Drain Tile System might be more appropriate.

The basement moisture barrier installation time can vary depending on the extent of the work and the size of your basement. However, our experienced team works efficiently to minimize disruptions to your home and landscaping.

Basement moisture barriers are designed to be durable and long-lasting. However, regular inspections can help ensure that the barrier remains effective. For example, ensuring that the barrier is not damaged and that all seams and edges are properly sealed is crucial.

The installation process for a moisture barrier on basement walls involves both interior and exterior steps to ensure a dry and secure basement.

Interior installation

• Clean the basement walls and floor, filling any cracks or holes with hydraulic cement.
• Install the moisture barrier (such as polyethylene sheets or rigid foam) against the wall, overlapping sheets by at least 4 inches and securing them with staples or tape.
• Seal seams and edges, especially around electrical outlets, pipes, and windows.
• Install insulation and framing over the barrier, ensuring it extends behind these components.

Exterior Installation

• Excavate a trench around the foundation to access the exterior basement walls.
• Power wash the exposed foundation, filling any cracks with hydraulic cement.
• Apply a robust, seamless polyurethane liquid membrane or polymer-modified bitumen coating to the foundation wall.
• Allow the membrane to cure, adding additional layers if necessary.
• Refill the trench with soil and install drainage systems like French drains or dimple boards.

When installing a vapor barrier in a basement, it is crucial to place it on the correct side of the wall to prevent moisture issues. For a basement wall assembly, the vapor barrier should be installed on the warm side of the wall, behind the insulation and framing. This helps to slow the movement of water vapor from the warm interior air to the cold concrete foundation walls, preventing condensation and potential mold growth. In contrast, a moisture barrier is installed on the cold side, directly against the concrete or block wall, to prevent groundwater from seeping into the insulation and framing.

Here are the key steps:

• Prepare the Wall: Clean the concrete wall thoroughly and fill any cracks or holes with hydraulic cement.
• Install the Vapor Barrier: Roll out the poly vapor barrier, overlapping sheets by at least 4 inches, and secure them to the wall using construction adhesive or mechanical fasteners. Ensure the barrier extends down to the concrete slab and is sealed around any penetrations like electrical outlets and pipes.
• Add Insulation and Framing: Install insulation (such as fiberglass, mineral wool, or foam board) and wood framing over the vapor barrier. This setup prevents warm air from coming into direct contact with the cold concrete wall, reducing condensation and the risk of mold growth.
• Seal Air Leaks: Ensure the wall assembly is airtight to prevent air leakage, which is a primary driver of moisture-related issues. Use an air barrier in conjunction with the vapor barrier to achieve this.

• Place the vapor barrier on the warm side of the wall, behind the insulation and framing, to prevent warm air from reaching the cold surface of the concrete foundation walls.
• Choose materials that allow for drying if moisture accumulates. For example, smart vapor retarders can prevent vapor diffusion from the inside out but allow moisture to dry to the interior when relative humidity in the cavity exceeds 60%. 
• Seal all seams and edges with vapor barrier tape and ensure the wall assembly is airtight to prevent air leakage. This is crucial as air leakage can drive moisture into the wall cavity, leading to condensation and mold growth.
• Use rigid insulation or foam board as a thermal break between the concrete wall and the wood framing. This helps in reducing condensation and prevents direct contact between the cold concrete and the warmer wood framing.

In addition to solutions against moisture barriers for basement walls, we provide basement leak repair and resealing basement walls. Our services also include installing basement window wells, egress windows, and window well coverings.