Clay brick makes an attractive exterior, but brick also can suffer from a wide variety of discoloring stains. Of these, the most typical is “efflorescence,” a surface deposit of whitish, powdery mineral salts. While this risk can’t be completely eliminated, there are smart ways to cut the odds of seeing it, and smart ways to respond when it does crop up.
Some mortars contain more than a trace amount of sodium or other salts. Avoid those, and specify low-salt mortars instead. Masonry block is another common source of salty minerals; if you apply brick cladding over concrete block, make sure to separate the two with a drainage material and an air space. If you get efflorescence anyway, don’t dawdle: when it’s fresh, the white powder easily rinses off with water.
Whether from cement, sand, or deicing salts found on the ground, salt appears as a visual problem only when it rises to the wall surface, carried by water in saturated brick. The deposit is left behind when the water evaporates. So keeping brick walls dry with overhanging eaves and capillary breaks helps prevent the problem.
Water-repellent coatings are risky. A coating can trap salts below the surface, where growing crystals can blow the face off the brick and create ugly spalling that is hard to fix.