Efflorescence is the 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



Identify and rectify the source of excess moisture, consider installing vents of exhaust fans where practical (particularly in kitchen, bathroom or laundry areas).

Remove the efflorescence and all 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. Dulux recommends the use of Weathershield® Matt for exterior surfaces.

More problem solving advice


Development of a yellow cast in aging paint solvent-based enamels


A rough, crinkled paint surface occurring when paint forms a 'skin'.

Tannin staining

Brownish or tan discoloration on the paint surface due to migration of tannins from the substrate through the paint film.