Masonry Magazine June 1989 Page. 22
Waterproofing interior surfaces below grade consists of applying proprietary portland cement base products to fill cracks, and seal the pores and voids of the masonry. Metallic oxide waterproofing compounds are also used. The oxide consists of pulverized cast iron, factory-mixed with a chemical oxidizing agent such as sodium peroxide. The waterproofing compounds are prepared by mixing the metallic oxide with portland cement and sand. This may be done in the field, or premixed factory products may be used.
The process for sealing the interior of walls is essentially the same for both the portland cement base products and the metallic oxide products. Existing flow of leaks must first be stopped. This is accomplished by first drilling weep holes near the floor line to relieve the water pressure. Next, a groove approximately one inch wide and deep is cut at the junction of the floor and walls. Existing wall cracks are then undercut to a minimum of 3/4 inch in depth and width. A stiff mixture of the waterproofing product is then packed into the cracks, and used to form a cove at the junction of the floor and walls. A parge coat of the sealer is applied to the walls beginning at the bottom, where the water pressure is the greatest. The parge coat is then cured a minimum of 24 hours. The weep holes are then packed to complete sealing the wall. For better appearance, an additional thin coat may be trowelled on to form a smooth finish.
Summary
The need for waterproofing concrete masonry may be reduced by designing structures to keep walls dry, and by good workmanship, especially in constructing mortar joints. Selection of waterproofing materials should be based on the mechanics of moisture flow through masonry walls. Above grade walls may be waterproofed with materials which resist penetration of rain, but permit water entrapped in the wall to evaporate to the outside air. Such materials include clear sealers, primer-sealers, latex paints, portland cement paints, and stucco. Preparation to assure a surface free of harmful contamination is a requirement for successful application of any type of waterproof coating.
Waterproofing walls below grade is best accomplished from the exterior of new construction before, backfilling. Exterior treatments include parging alone, or in combination with a bituminous coating. Built-up membranes of bitumen and fabric may be used in case of hydrostatic head, or an elastomeric membrane may be utilized. For walls inaccessible from the exterior, waterproofing of the interior surface may be accomplished through application of proprietary compounds having portland cement or metallic oxide bases.