What cleaning does
It removes algae, lichen and moss from the surface. On a roof where those are heavy, that is a real cosmetic improvement and, for lichen and moss, a modest protective one. That is the whole list.
What cleaning does not do
- Restore granules. A shingle roof that has lost its granules is pale because the granules are gone. Cleaning removes the algae from what is left; it does not put anything back. A cleaned, worn shingle roof is a clean, worn shingle roof.
- Fix a leak. None of the things that leak - boots, flashings, seams, crowns, valleys - are affected by cleaning in any way.
- Extend the underlayment's life. On tile, the waterproofing is underneath. Cleaning the tile has no effect on it, and pressure washing actively harms it.
- Reset the clock on anything. A roof that is due for replacement is due whether or not it is clean.
Where this goes wrong
The failure mode is not that people clean their roofs. It is that a freshly cleaned roof looks fine from the street, and "looks fine from the street" gets mistaken for "has been looked at". A pressure-washing crew is not inspecting anything. They are removing what is visible and leaving what is not.
The right order
Inspect first, so you know what condition the roof is actually in and whether cleaning is even sensible - a shingle roof in its last years does not need its remaining granules disturbed. Then, if you want it cleaned, have it soft-washed by someone who knows what they are walking on. Then have it looked at again, because cleaning is when tile gets cracked.
KLR does not wash roofs. We arrange it through a vetted third party for members who want it, and we inspect before and after.
Start with the inspection. If the roof would benefit from a clean, the report will say so, and we can arrange it.
Compare the plans