POSSIBLE CAUSES:
Solvent-based paint or water-based paint was applied to excessively damp masonry. Damp masonry surfaces are alkali active.
Fresh masonry is likely to contain lime which is extremely alkaline.
Until the lime has a chance to react with carbon dioxide from the air, the alkalinity of the masonry remains so high that it can attack the integrity of the paint film.
Strong alkali can attack the resins in some solvent borne paints and may also attack certain pigments causing colour to fade
SOLUTION:
Ensure that any defects which all allow moisture into the substrate that are fully cured.
Apply an alkali resistant paint.
If it is not possible to allow sufficient drying of the substrate, use a moisture vapour permeable Sandtex Trade product and avoid using strong colours.
