Concrete Waterproofing Built-up Systems

When I first went into the waterproofing business, I did a number of jobs with a hot-mopped, asphalt-and-felt built-up system. With these systems, you first apply a concrete primer. You then mop on a coating of hot tar (which is heated in a large asphalt kettle), followed immediately by application of a sheet of perforated felt, extending the system right out onto the footing. You keep staggering the felt sheets until you have three layers of felt with a final coating of tar. (The local building code may let you get by with only two plies.)

This is a good system with a lot of strength, but probably not much elongation ability. You can produce a similar built-up waterproofing system using cold, trowel-grade dampproofing and reinforcing fabric. Again, this system has some strength but little elasticity.

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