Roof Soft Washing

Moss grows on Oregon roofs faster than almost anywhere else in the country. It holds moisture against shingles, lifts the edges, and lets water penetrate the underlayment. Left untreated, moss can cut 5-10 years off a roof's lifespan. Most composition shingle manufacturers recommend keeping roofs clear of moss to maintain warranty coverage.

We use low-pressure soft washing with sodium hypochlorite solutions to kill moss and algae without damaging shingles. The solution is applied from a ladder at the roof edge or from the ground using extension wands — we don't walk on the roof unless absolutely necessary, because foot traffic breaks granules loose and accelerates wear. The chemicals do the work. Moss dies within a few days and weathers off naturally over the next few weeks, or we can rinse it off immediately if you prefer a faster visual result.

“Moss holds moisture against shingles and lifts the edges — left untreated, it can cut 5-10 years off a roof's lifespan.”

Metal roofs and tile roofs get the same treatment but with adjusted chemical concentrations. Metal doesn't hold moss as aggressively, but algae staining is common. Tile roofs grow moss in the valleys and along the edges where debris accumulates.

Zinc or copper strips installed at the ridge can slow moss regrowth, but they're not a substitute for cleaning an already-mossy roof. We install strips if requested, but the existing moss needs to be killed first.

AWP Exterior Cleaning services roofs across Oregon and Western Washington. North-facing slopes and shaded roofs in both states need cleaning more often than south-facing slopes that get full sun. Coastal properties deal with heavier moisture and faster regrowth than valley properties. We schedule roof cleaning during dry weather windows — the chemicals need 24-48 hours without rain to work properly.

Typical roof cleaning costs $400-$800 for single-family homes depending on roof size and pitch. Steep roofs or multi-story homes cost more due to setup time and safety equipment. Most Oregon roofs need cleaning every 2-3 years. If you're seeing black streaks or green patches, the moss is already established and needs treatment.