Causes The symptom includes crusty white salt particles or white wet stains which leak from cracks or tuckpoints. These white salty particles are called efflorescence and are resulted from high humidity that exists before refinishing, trapped water in the wall or damp original surfaces. Cracks or leaks also allow moisture from either the ceiling or the other side of the wall. Area which tends to encounter the problem is basement room. The more leaks, the more white salt particles.
Solution Fix the leaks first. Wash and clean the efflorescence. Wipe the surfaces clean with acid dilution and scrape off with a stiff brush. Wash with clean water or power washing. Leave dry. Should the humidity persists when the leakage is fixed, drill tiny holes on the wall to let moisture evaporate. This will help prevent the refinish from becoming swollen or peeling. Alternatively, use heat such as those from a spot light, to boost the evaporation. Fix the holes or cracks with fine wall putty for exterior. Repair the leaks. Apply the primer on original surface and refinish.