White Powder on Brick or Pavers (Efflorescence)

What it is

Efflorescence is salt. The Brick Industry Association, the trade group for American brick makers, explains that it shows up “when water containing dissolved salts is brought to the surface of masonry, the water evaporates and the salts are left” behind (BIA Technical Note 23A).

It shows up on brick walls, block foundations, retaining walls and concrete pavers. It is usually white and powdery, and it often sits in a band near the ground or under a spot where water runs down the wall.

Is it hurting the brick?

Usually not. The BIA says that “although undesirable, efflorescence is usually not harmful to brick masonry” (Brick Industry Association). It is a sign of water, though, and water is what does the damage over time.

New brick or old brick

The BIA calls efflorescence on brickwork less than a year old “new building bloom.” In most cases it “will dissipate over time” as the wall dries. When it shows up more than a year after building, the BIA says it usually points to “excessive water penetration or poor drainage,” and that it is often worst in winter (Brick Industry Association).

So on an older house, look up before you look at the wall. An overflowing gutter, a missing downspout extension or a sprinkler hitting the brick is often the source.

How it comes off

The BIA says most of these salts dissolve in water, many disappear with normal weather, and what stays “usually can be removed by dry brushing.” Heavy buildup takes a cleaner made for brick, tested on a small area first (Brick Industry Association).

Two warnings matter for anyone washing it:

• The Brick Industry Association says it is “usually not advisable to wash efflorescence off the brickwork except in warm, dry weather,” because the extra water can bring more salt to the surface.
• High pressure is the wrong tool on brick and mortar. The National Park Service’s guidance on cleaning masonry says to start at very low pressure, “100 psi or below,” and generally go no higher than 300 to 400 psi (NPS Preservation Brief 1).

We remove efflorescence on brick, block and pavers. If your house is older, with soft brick or lime mortar, read cleaning old brick and mortar first. For pavers, see how to clean concrete pavers.