What is Efflorescence?
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Efflorescence is the white, powdery deposit that appears on the surface of brickwork, plaster or concrete when soluble salts inside the material are dissolved by water, carried to the surface, and left behind as the water evaporates. It is a moisture-and-salt problem, not a paint problem.
What causes it
Two things have to be present: soluble salts and water to move them.
- Salts come from the bricks, the sand, the cement or even the mixing water.
- Water — rain, rising damp, or trapped construction moisture — dissolves the salts and wicks them to the surface, where it evaporates and dumps the salt as a white bloom.
New masonry often shows some efflorescence as it dries out; persistent efflorescence points to an ongoing source of moisture, such as rising damp past a failed DPC or a leak.
How to remove it
- Dry-brush the loose deposit off with a stiff brush (do not just wet it, which redissolves the salt and drives it back in).
- For stubborn deposits, a dilute mild acid wash (proprietary efflorescence remover) followed by clean water can be used with care.
- Fix the moisture source — otherwise it simply returns.
How to prevent it
Use low-salt bricks and clean, low-silt sand; keep a sound damp-proof course; ensure good drainage and drip moulds so water is thrown clear of the wall; and let new work dry before painting. Painting over active efflorescence traps salt behind the film and lifts the paint.
Frequently asked questions
What is efflorescence? The white salt deposit on masonry, plaster or concrete formed when water dissolves soluble salts, carries them to the surface, and evaporates.
What causes efflorescence on walls? Soluble salts in the bricks, sand, cement or water, combined with moisture (rain, rising damp or construction water) that carries them to the surface.
How do you remove efflorescence? Dry-brush the loose deposit, use a dilute mild acid wash for stubborn areas, and — crucially — fix the moisture source so it does not return.
Is efflorescence harmful to a building? The bloom itself is mostly cosmetic, but it signals moisture movement; persistent efflorescence indicates a damp problem that should be traced and fixed.
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CivilSite Editorial Team✓ Engineer reviewed
Written and reviewed by practising civil engineers with 10+ years of Indian residential construction experience.