2. Do NOT pressure wash your roof when attempting roof cleaning.
While many choose to hire those specialized in roof cleaning services, some wish to maintain their roofing themselves. Please beware of pressure washing your roof.
Removal of Lichen and moss by jet washing will invariably remove the granular surface finish and potentially damage the structural integrity of the tile, this process followed by a surface treatment application would invariably invalidate any tile manufacturer’s guarantee. Interlocking roof tiles are not designed to be walked upon,foot traffic can cause these interlocks to break opening the roof up to water ingress.
In appropriate pressure washing can potentially force water up between the tiles and roofing felt into the roof space. Bedded mortar and
flashings can also be blasted off using this method, potentially leading to further costs for rectification.
Effectively, the only way to safely clean your roof and the tiles or shingles on it is to use a 6" trowel and wire brush and do it manually by hand or use a light chemical with low pressure not to exceed 1200 psi at a minimum distance of 12 inches from the surface. Pressure washing can decimate shingles and eroding it’s life expectancy invalidating any warranty.