Efflorescence on the surface of brick is usually not harmful by itself. The Brick Industry Association says it is usually not harmful, but that salt crystals forming inside the brick can cause cracking and distress. It also tells you water is moving through the wall. On a wall more than a year old, a new bloom usually points to excess water or poor drainage, and that is the part worth fixing.
Efflorescence is usually not bad for brick by itself. The white powder on the surface is salt left behind when water evaporates, and BIA says it is usually not harmful (BIA Technical Note 23A). What matters is what it tells you: water is moving through your wall, and that water can do damage the powder does not.
When efflorescence is just cosmetic
On the surface, it is a stain. NPS and BIA both describe surface efflorescence as relatively harmless (NPS and BIA). Cosmetic cases tend to look like this:
- It appeared within the first year after new brickwork, tuckpointing or repairs. BIA calls this "new building bloom" and says it usually fades (BIA Technical Note 23A).
- It is a light dusting that comes and goes with the weather.
- The brick face is firm, the mortar is sound, and nothing is flaking.
When it is a warning
Efflorescence that shows up after the wall is more than a year old usually points to excess water getting in or poor drainage, and it is often worst in winter (BIA Technical Note 23A). That is the wall telling you about a leak.
The damaging form is hidden. When salts crystallize inside the brick instead of on the surface, they can crack the brick or make the face spall or delaminate (NPS and BIA). NPS shows this most clearly on soft brick behind mortar that is harder than the brick: moisture and salts have nowhere to go but out through the brick (NPS Preservation Brief 2).
Take a closer look if the powder comes with:
- Flaking, sanding or popping brick faces. See freeze-thaw damage to brick.
- Crumbling or missing mortar.
- Damp or stained interior walls.
- Powder in the same spot every year.
Fix the water source before you clean. BIA says to find and fix the moisture and salt cause before removal, and that coatings alone are not recommended (BIA Technical Note 23A). Our post on how to remove efflorescence from brick covers cleaning, and water coming through a brick wall covers leaks.
How to tell which one you have
You cannot tell from the powder alone, so look at the wall around it:
- How old is the brickwork? Under a year since new work, a bloom is expected. Older than that, treat it as a clue.
- Where is it? Powder below a parapet, chimney, window sill or gutter points at water coming from that spot.
- Is it seasonal? BIA notes it is often worst in winter (BIA Technical Note 23A), so photograph it in more than one season.
- Is the brick itself changing? Run a fingernail over a flaking face and look at the mortar. Soft, sanding brick or missing joints mean the wall needs a mason, not a brush.
Chicago also requires masonry joints to be kept weather resistant and water tight (City of Chicago, 14X-3-303), so open joints that let water in are a repair item whether or not powder shows up.
If the powder is on a wall you cannot explain, our masonry crew can look at where the water is coming from. The Chicago brick and masonry guide covers the whole system.
Common questions
On the surface, usually not. BIA calls it usually not harmful. But salt crystallizing inside the brick can crack it or make the face spall, and the water carrying the salt can damage the wall in other ways.
Yes, find out why. BIA says efflorescence that appears after the first year usually points to excess water getting in or poor drainage. The powder is the symptom, so look at joints, gutters, copings and drainage.
No. BIA says it usually originates from the mortar, backing, soil or trim, not the brick, and is usually not harmful. It is a sign of moisture, so check the wall for open joints, leaks and drainage problems.
Sources
- Brick Industry Association: Technical Note 23A: Efflorescence, Causes and Mechanisms (PDF)
- National Park Service: Preservation Brief 2: Repointing Mortar Joints in Historic Masonry Buildings (PDF)
- City of Chicago: Code Modernization Ordinance, including Title 14X Minimum Requirements for Existing Buildings (PDF)
Facts last checked: October 7, 2026.
This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.