Waterproofing vs. Damproofing

Americans spend thousands of dollars to repairing basement leaks after their homes are built each year. Surprisingly, many believe that their waterproofing failed when in fact, their foundation was treated with only low-cost damproofing.

What is Dampproofing?

Damproofing is a low-cost asphalt cutback or emulsion type product that is applied paper thin, 10 mils or less, to foundation or cavity walls to retard the infiltration of water vapor into the living space area. Damproofing was never designed to protect walls from water leakage. These compounds are usually quite brittle and do not have crack bridging capability or the integrity to resist hydrostatic water pressure. When walls start to settle, shrink, and crack, dampproofing can not expand to bridge the crack and its film opens up to allow water infiltration. 

Building code officials around the country are re-examining the use of traditional dampproofing that was adopted back in the 1940’s. Because of the problems and expense home owners have experienced over the past decades, new waterproofing codes are continuing to be implemented to address this problem.

The Benefits of Waterproofing

There are many different types of waterproofing materials available to the industry today. They range from sheet membranes to urethanes and many in between. The most common however is polymer modified asphalt. Asphalt has been used for centuries to seal and waterproof and its use today has been drastically improved from the ability to modify it with various elastomeric polymers which allow the material to stretch and improve its strength as well as it’s resistance to damage and aging.

Waterproofing is applied at 4-6 times the thickness of a damproofing material. It’s cured film bonds tightly to the foundation wall and provides a tough and highly elastic barrier to prevent the infiltration of both water and moisture vapor through the wall structure into the building interior. When water builds up along the foundation wall, hydrostatic pressure is created that if not relieved, will penetrate through damproofing and non-treated walls resulting in wet inner living spaces and damage to building contents. Waterproofing’s tough film resists this pressure to keep living areas dry. When concrete or masonry walls crack, and they all do, Waterproofing will stretch to bridge normal cracks to prevent moisture infiltration.

While Waterproofing is considerably more expensive initially than Damproofing, its long term cost is significantly lower. The cost to dig up a foundation and repair damage to structures and contents can range in the many thousands of dollars. The health hazards created by moisture, a leading cause of mold and mildew, can cost many thousands more.

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