How to use cituminous coatings to waterproof

Bituminous coatings, either hot- or cold-applied, will give protection where dampproofing only is necessary, provided the surfaces on which they are used are smooth. Rough walls should be given a grout coat of cement mortar and allowed to dry before the bituminous coating is applied. Bituminous coatings should be used only on the outside of either masonry-unit or monolithic walls because such coatings on the inside walls of basements are likely to blister or peel.

Cold-applied coatings may be of heavy-brushing or troweling consistency, with asphalt or coal-tar pitch as the base. Before applying brushed or troweled coatings the wall should be primed, using an asphalt primer with asphalt coatings and a coal-tar or creosote primer with coal-tar coatings. Bituminous coatings may also be applied to cement-mortar coats.

Hot-applied coatings of asphalt or coal-tar pitch when properly applied are superior to cold-applied coatings, because they usually provide more bitumen per unit area than the cold-applied coatings. Walls should be smooth and dry and should be primed, using an asphalt primer for coal-tar pitch coatings.

The hot-applied coatings are “mopped-on” with a roofer’s mop, in one or more applications, to a thickness of at least one-eighth inch.

When there is water pressure against the walls from a spring or other source, the most effective treatment for the walls is a so-called bituminous membrane. It is made with three or more layers of asphalt or coal-tar saturated felt or fabric, cemented to the wall and to each other, and coated with asphalt or coal-tar pitch. Walls should be prepared as described for single hot-applied coatings.