What is that white powder that appears occasionally on brick walls?
A. This is called efflorescence and is a deposit of soluble salts. Although unsightly, it is usually easily brushed or washed off. Often, efflorescence will occur on newly built walls as they dry out (“new building bloom”). Recurring efflorescence can be a cause for concern in that it indicates moisture in the wall which can ultimately cause deterioration of the wall system. Common sources of moisture include leaking roofs or downspouts, sprinkler systems, runoff from horizontal surfaces, and interior moisture leaking through the air/vapour barrier. See BIA Technote 23A for further information. Q.
