Have you ever noticed this cloudy deposit on brick walls before? It’s called efflorescence. This is the salt and other dissolved material that is left behind when water evaporates. But how does it get on brick walls?
On a newly built brick wall it can come from the water in the mortar evaporating. It’s common to see efflorescence on newer brick walls for a short while after they are built. It's a temporary issue.
On walls that have been around for years, it’s a sign that one a handful of things are happening. The first is that water is hitting the surface of the wall from the outside. This could be from a faulty eavestrough or downspout sending water to the surface of the wall. Another potential cause is a significant source of moisture inside which is working its way through to the outside of the wall. Yet another common cause is capillary action. Old brick foundations were not built with much in the way of damp-proofing. Ground water from the backfilled soil can soak into the brick wall. While much of that water works its way inward to the basement, a significant amount of water can be pulled upward through the brick by capillary action. Once it gets to the top it evaporates out of the wall, leaving the dissolved minerals behind. This video shows capillary action in… well, action:
Time lapse film of moisture rising brick by capillary action
When efflorescence is noted, it’s important to understand the cause and take corrective action against the troublemaking water. Not only is water a cause for mold growth and material deterioration. Any water inside the brick that is exposed to freezing temperatures could freeze and expand. The freeze/thaw cycles that we see in our winters could cause surface breakage, or spalling, of the surface of the brick and deteriorate mortar joints. When efflorescence, spalling, or deteriorated mortar joints are noted during an inspection, every attempt is made to determine what the potential sources of water are and how to correct it to prevent further material deterioration.