Basement Waterproofing Systems

Crushed stone is an important part of a basement waterproofing system that will help create a capillary break between the soil and the underside of the concrete foundation slab. Building codes for new construction require the installation of a vapor barrier under the slab. This should prevent water vapor from diffusing into the basement through the slab over the life of the building. A foundation drainage system will direct water away from the foundation.

On foundation walls both damp proofing and waterproofing can be used depending on code, soil type and climate. Damp proofing is sufficient in soils with free drainage under dry conditions. Damp proofing creates a capillary break between the concrete and the soil, which slows water vapor diffusion and the capillary transport of liquid water. A damp-proofing coating of the foundation wall is typically an asphalt-based material, and can be manually applied or sprayed on. It is not intended to resist constant hydrostatic pressure. When water pools frequently or the soil holds water, waterproofing is recommended.

A waterproofing membrane blocks liquid water and water vapor. Waterproofing may be required in soils with high moisture content due to higher hydrostatic pressures. Waterproofing materials have the ability to bridge cracks and withstand hydrostatic pressure. The products are more durable and flexible than damp proofing materials. A common basement waterproofing system is a thick, modified bitumen asphalt coating that is spray or roll applied. Another basement waterproofing system includes attaching a synthetic polymer membrane using mechanical fasteners or adhesives.

An additional level of water protection is provided by more sophisticated materials that provide both waterproofing and vapor flow resistance to protect against high soil moisture content. These products, like Platon from CertainTeed, incorporate a waterproofing membrane with a dimpled surface that faces the foundation wall. The waterproofing membrane blocks liquid water and water vapor. The dimpling creates an air gap between the membrane and the foundation wall. A capillary break and drainage space is created between the soil and the concrete surface. The air gap allows the concrete foundation wall to dry outward by allowing water vapor to condense on the surface and drain to the bottom of the assembly. Be sure to utilize a basement waterproofing system during contstruction in order to protect against water damage and flooding in the future.