This refers to the crusty, white salt deposits that may be leached from mortar or masonry as water passes through it.
- Failing to adequately prepare the surface by removing all previous efflorescence.
- Excess moisture escaping through the exterior masonry walls from behind.
If excess moisture is the cause, eliminate the source of the problem by repairing the roof, cleaning out gutters and drainpipes, and sealing any cracks in the masonry with a high-quality, water-based all-acrylic or siliconised acrylic sealant.
If moist air is originating from inside the building, consider installing vents or exhaust fans, particularly in the kitchen, bathroom and laundry.
Remove the efflorescence and any 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 or primer, and allow it to dry completely. Follow this with a coat of top-quality exterior house paint, masonry paint, or elastomeric wall coating.