What is actually growing on your roof
| Growth | What it looks like | Why it matters |
|---|---|---|
| Moss | Thick green or brown cushions, usually on shaded slopes and along shingle edges | Holds water and can lift shingles |
| Algae | Dark streaks, often running down the roof | Mostly cosmetic early on, and a sign of a damp roof |
| Lichen | Crusty gray, green or orange patches that grip the surface | Hard to remove and can hold moisture |
Soft wash, not pressure wash
The usual professional method is a low-pressure soft wash: a cleaning solution is applied, the growth dies, and it is rinsed off. High pressure can strip the protective granules from asphalt shingles, and OSU Extension cautions that improper pressure washing can damage shingles. Read more on soft wash roof cleaning.
What a roof cleaning should include
- Moss removal, with thick moss brushed or blown off
- Treatment or soft wash of the whole roof surface
- Protection for plants, windows and the area below
- Gutters and downspouts cleared, if you ask for it
- Cleanup, with debris hauled away
How much does roof cleaning cost in Salem?
HomeAdvisor lists a Salem average of about $420, with a typical range of $290 to $573. Roof size, pitch, access and how much moss there is all move the price. See the cost guide.
How often?
It depends on shade. Shady, tree-covered roofs may need attention every couple of years, and OSU recommends an annual maintenance routine after moss removal. See prevention.
Should you clean, or is the roof past saving?
Cleaning will not repair worn-out shingles. If granules are heavily gone, shingles are curling or leaks have started, a cleaning will not fix it. A roofer can tell you whether the roof has life left. See also roof types and moss.