These treatments will have to be renewed periodically. It should be emphasized that an essential part of the treatment for damp walls is the filling of structural cracks, renewal of caulking around windows, and the repair and correction of faulty drains and flashings. Summary Rain penetration of walls of unit masonry is a common problem, which may arise for several reasons. When units and mortar are not completely bonded together penetration may occur at the interface. In addition, when permeable units are used, leakage may take place through them.
Structural cracks form yet another path for rain penetration.
In the design of a building consideration should be given to the possibility of stresses being set up in the masonry from differential movements of various parts of the building. When possible, the movements should be accommodated without stressing the masonry, in order to avoid cracking. Suitable design of a building for rain resistance also calls for the provision of adequate flashings and of complete caulking at wall openings. In construction of the masonry, particularly brick masonry, steps can be taken to obtain complete bonding between unit and mortar and thus prevent interface leakage. Cavity wall construction affords a means of obtaining resistance to rain penetration and walls of this type have come into extensive use where severe exposure to rain has caused leakage problems in solid walls.