Paint With Confidence

Exterior Common Issues & Solutions

Efflorescence/Mottling

Text & image courtesy of the Rohm & Haas Paint Quality Institute

Efflorescence/Mottling

Crusty, white salt deposits, leached from mortar or masonry as water passes through it.

Possible Cause

  • Failure to adequately prepare surface by removing all previous efflorescence.
  • Excess moisture escaping through the exterior masonry walls from the inside.
  • Air pollution, car exhaust and flying dust collecting on house body and horizontal trim.

Solution

If excess moisture is the cause, eliminate the source by repairing the roof, cleaning out gutters and downspout, and sealing any cracks in the masonry with a high quality, water-based all-acrylic or siliconized acrylic caulk. If moist air is originating inside the building, consider installing vents or exhaust fans, especially in kitchen, bathroom and laundry areas. Remove the efflorescence and all other loose material with a wire brush, power brush or power washer; then thoroughly rinse the surface. Apply a quality water-based or solvent-based masonry sealer and allow it to dry completely; then apply a coat of top quality exterior house paint, masonry paint or elastomeric wall coating. (Elastomeric wall coatings should not be applied to surfaces that may have excessive moisture coming through, such as soil retaining walls, uncapped walls or interior basement walls).