Many times the terms waterproofing and damp proofing are used interchangeably. The terms waterproofing and interior water diverting are also used interchangeably. All of these terms sound like they accomplish similar goals, though they do not. Understanding these terms is critical if you want to keep your foundation dry and structurally sound. Knowing what these methods can and cannot do allows you to pick the best method for your home.
Years ago many homes were spray coated with solvent-based asphaltic products. These materials didn’t actually waterproof foundations, they damp proofed them. These asphaltic coatings only prevent the transmission of water vapor into the concrete. Waterproofing materials prevent the transmission of both liquid water and water vapor. Now, many so called waterproofing companies attempt to divert the water that damp proofing does not stop. These interior water drainage systems do not prevent water from coming through the concrete. They are designed around the fact that water is coming through the foundation and they divert this water to a sump pump that expels the water outside the structure. Obviously this is contradictory to the definition of what waterproofing is.
Today the most commonly used material is a rubberized asphalt coating that can be sprayed on or used as a peel and stick sheet product. Whether using the spray or sheet rubberized asphalt it must be protected from ultraviolet light so it must be covered and protected when exposed to sunlight. Next are polyethylene sheet membrane systems. These are three layer systems with the two outside made of high density virgin polyethylene sandwiching a layer of recycled polyethylene.
No matter which of these systems that you use it needs to be protected from damage from backfill, to insulate basements and provide water drainage away from the membrane. Soils with high water content produce significant hydrostatic pressures against foundation walls. This hydrostatic pressure can cause water to penetrate the smallest holes and cracks. Thus waterproofing actually consists of a waterproof membrane and drainage next to this membrane which moves water to the exterior drain located alongside the footing.
This system of waterproofing is even more important these days due to the fact that homes are sealed tight. Building homes tighter in order to conserve on energy increases the problems of mold and mildew growth because relative humidity increases inside the building envelope. Stopping water from entering a basement makes a true waterproofing system a must these days. Waterproofing, not damp proofing or water diverting is the answer to a healthy and dry home. Knowing what is available and what is necessary for your home is the key to making your home dry and safe.