Over time the roof of your home may become dirty, and you start to see a build-up of moss.  The first thing you think of doing is pressure washing the roof. You pressure wash the patio, so what harm is there?  STOP! 

Here are some reasons why you shouldn’t pressure wash your roof.

Roof tiles have a sandy finish, which wears off gradually over an 80-100 year period.  When you pressure wash them, you decrease the lifespan of the time.

You risk cracking or loosening the tiles, which can cause additional issues, as highlighted below.  You also run the risk of breaking the bond between the tiles.

The force of water from a pressure washer could cause a leak into the attic space. This is especially true if any of the tiles are lose or broken or you crack one in the cleaning process.

If you have an extended warranty on your roof, you may want to check the exclusions to see if high-pressure washing will invalidate it