As the industry changes, so must we.

Contractors are often asked about the best way to clean a tile roof.  Below is a recent question submitted through our “Ask the Expert” form and the response from TRI President and Technical Director Rick Olson.


“Our contractor suggests water blasting of tile roof to remove dirt and what I will assume is mold. Can chlorine be used on tiles or will there be a risk of streaking the tiles?”

moss on a tile roof

An extreme example of unchecked moss and tree debris on a 30-yr roof in a cool humid climate.



The cleaning of tiles with pressure washers is a common practice as regular roof maintenance. Since roofs are slippery when wet, the work should be performed by a qualified roofing professional. The use of diluted chlorine can be used to help remove the final algae that might be present, but we have seen just plain water used as well. The pressure washer should not be above 1300 psi as it can create surface wear. The dirt, algae or moss that grow on the surface of the tiles are not affecting the condition of the tiles. It is more an aesthetic issue that homeowners wish to remove.


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