Efflorescence is crusty, white salt deposits which are leached to the surface of mortar or masonry as water passes through it. Efflorescence is often seen as a white, fluffy deposit of salt crystals on cementitious (e.g., masonry) wall surfaces. Efflorescence depends on the presence of salt and moisture, and the growth of crystals will continue as long as both are present. The salts are present in the mortar, blocks or concrete structure, and the moisture is usually attributable to some building defect. When emanating from mortar in brick or block buildings, efflorescence will appear as narrow bands corresponding to mortar joints.
- Failure to adequately prepare surface by removing all previous efflorescence.
- Interior moisture escaping through exterior masonry walls.
- Exterior moisture driven through masonry walls by wind and rain.
- Basement walls that are not properly sealed against ground moisture penetration.
- Insufficient curing time for new cement or mortar.
If excess moisture is the cause, eliminate the source by repairing the roof, cleaning out gutters and downspouts, and sealing any cracks in the masonry with a quality caulk or sealant.
If moisture is originating inside the building, consider installing vents or exhaust fans, especially in kitchens, bathrooms and laundry areas.
If moisture is being driven through the walls from the outside, apply a waterproofing coating to the outside.
Remove efflorescence and all other loose material with a wire brush, power brush or low pressure-washing, and then thoroughly rinse the surface.
If the surface is highly alkaline, wash with a mild solution of a phosphoric acid or muriatic acid.
Painting should be delayed if efflorescence continues.