What is the crusty white powder I see on my walls?

What is it?

These crusty white deposits, or efflorescence, are caused by salts leaching from the mortar or masonry as water passes through it. 

What are the possible causes?

  • Not removing all traces of previous efflorescence while preparing surface for painting.
  • Excessive moisture rising to the surface of the wall from within.

How can I fix this problem?

  • Eliminate sources of moisture near the wall by fixing the roof, sealing cracks and cleaning gutters and downspouts. Use a good quality water-based acrylic or siliconised acrylic caulk.
  • If moist air is coming from within the building, especially from bathrooms, kitchens and laundry rooms, install vents and exhaust fans to minimise it.
  • To treat efflorescence, remove all traces of it first with a wire brush or powerwasher. Rinse surface thoroughly.
  • Apply a masonry sealer and once it is completely dry, coat with a high quality exterior paint.