The chalky substance is the result of your roof tiles undergoing a natural process called efflorescence. It’s a temporary surface condition that is common with all concrete products. The chemical nature of cement causes it to happen and in no way affects its quality, function, or structural integrity. It’s difficult to estimate how long the effects of efflorescence will last, but rainwater and carbon dioxide will gradually remove the deposits, leaving the tile’s original color intact.
What is the white chalky substance on my concrete roof tiles?