Efflorescence – The Natural Graffiti
*Note: This is an actual photo. It has not been altered in any way.
What is it?
Efflorescence (from the French meaning “to flower out”) is a fine, white, powdery deposit of water-soluble salts left on the surface of masonry as the water evaporates.
Efflorescence is one of the most misunderstood conditions encountered. Although it is often a sign of water intrusion on existing buildings, as water can drive soluble salts to the exterior surface from within resulting in the typical “white powder” observed, there are often other dynamics that can actually be the cause for these conditions.
How Efflorescence Forms
All masonry building materials (brick, cement, stone, stucco, mortar) contain natural salts (mostly, sodium, calcium chloride). It isn’t until water is introduced (through rain, sprinklers, household leaks, etc.) that these salts become a problem.
The sulfates in the wall are dissolved by water into a solution which then moves through the natural pores in the masonry. The solution moves to the surface of the wall where the water evaporates, depositing the salts on the wall and producing the white powder we know as efflorescence.
While efflorescence can occur year-round, it typically forms during cold, dry weather. Why? Cold, dry air draws moisture out of the materials where it evaporates, depositing the salt as a white crystalline growth on the surface.
According to the Masonry Institute of America, three conditions must exist before efflorescence will occur:
- There must be water-soluble salts present somewhere in the wall.
- There must be sufficient moisture in the wall to render the salts into a soluble solution.
- There must be a path for the soluble salts to migrate through to the surface where the moisture can evaporate, thus depositing the salts which then crystallize and cause efflorescence.
All three conditions must exist. If any one of these conditions does not exist, then efflorescence cannot occur.
How do I prevent it?
While nothing has proven 100% effective against efflorescence, measures can be taken to reduce the effects of the above three conditions. If these circumstances can be controlled, there should be no efflorescing of your masonry walls.
- Reduce all soluble sulfates
- Use good details to prevent water from entering the masonry (seal the building once efflorescence is removed)
- Use good construction practices to eliminate paths for moisture
The good news is most efflorescence conditions (whether observed on existing buildings or new construction) will eventually go away in time. This is especially true if the source(s) of water intrusion in existing buildings leading to the conditions observed are effectively repaired.
How do I remove it?
Unfortunately, despite all efforts, efflorescence may still occur. There are cleaners available, however, that can remove the soluble salts (efflorescence) effectively and PCM does perform this service often. We typically recommend performing a small test mock-up with the cleaning solution followed with observation over a period of weeks (or longer in the winter/rainy months) if the condition is widespread, as this will determine if the condition returns. Furthermore, this will determine if further investigation or water intrusion repairs are necessary.
If the salts are water soluble, the best removal method is with a dry brush. If the efflorescence is in small spots or limited areas, hand washing with a mild detergent and a stiff bristle brush should get the job done.
While cleaning efflorescence from the walls is an immediate fix, it will not cure the problem. After cleaning, the efflorescence may reappear unless the natural efflorescent chain is broken. In addition to proper detailing and maintenance, application of water repellents can help prevent moisture from entering the masonry and rendering the sulfates into solution.
In summary, efflorescence is a harmless, yet unattractive, buildup of soluble salts on masonry surfaces. Its presence indicates excess water, a condition that can damage the interior of your building, and therefore efflorescence removal and leak inspection should take place as soon as possible.