Painting a brick masonry wall can do more harm than good, by trapping moisture which damages the wall's surface.
Q: I never understand why people paint brick masonry. When brick masonry is painted, it must be maintained more frequently to replace areas of paint that have chipped, peeled, or are otherwise defaced. I have heard that painting masonry walls may help the walls last longer, especially when the brick is not durable to begin with. Does this work? Or does painting brick actually make the masonry more susceptible to damage by holding moisture in?
A: Being someone who truly appreciates the beauty of a brick masonry wall, I am not a fan of painting brick masonry. Once brick is painted, it becomes a maintenance issue. Painted masonry must be re-coated far more frequently than unpainted masonry needs to be repointed or repaired. Paint will not make brick masonry more durable; it will likely have the opposite effect. When you paint brick masonry, it slows down the evaporation of moisture from the face. This can hold moisture within the wall. Entrapped moisture can allow the wall to undergo more freeze-thaw deterioration and can cause efflorescence to build up in the masonry, resulting in damage from salt recrystallization. Brick Industry Association's Technical Notes on Brick Construction No. 6, Painting Brick Masonry, states that in most cases, repainting brick masonry is required every three to five years. It also states that it is wrong to assume that painted brick masonry walls can be built with less durable materials. In fact, when brick is to be painted, the materials must be of the highest quality, or at least as good as masonry walls that are left exposed.
Norbert V. Krogstad
Principal at Wiss, Janney, Elstner Associates Inc.