I have seen many buildings where efflorescence is worse on the north elevation. Why is this?
Three conditions influence efflorescence. The brick or mortar must contain soluble compounds or salts that can be deposited on the face of masonry; significant amounts of water must penetrate the masonry; and the water must remain within the walls long enough to dissolve the soluble compounds. There are a few reasons why the north elevation may have worse efflorescence. Depending on the region of the country, the north elevation may receive more wind-driven rains than other elevations. The north elevation also is likely to hold water in the wall longer, because it does not receive direct sunlight that can dry out the walls quickly.