Moss on a roof in Arizona is a curiosity. Moss on a roof in Lewis County is a countdown. We get the damp, shaded, mild winters that moss is built for, and once it takes hold on an asphalt shingle it does not simply sit on the surface — it grows into the mat, holds water against the shingle permanently, and gradually lifts the lower edge of every course it gets under.
Once the edge is lifted, the next wind-driven rain goes underneath rather than over the top. That is the mechanism by which a twenty-five-year roof starts leaking at year fourteen. The stain that eventually appears on a bedroom ceiling is the last step in a process that began several winters earlier on a north-facing slope nobody looks at.
The instinct is to blast it off with a pressure washer. Do not. Asphalt shingles are protected by the mineral granules bonded to their surface, and those granules are what stop UV light destroying the asphalt underneath. A pressure washer removes the moss and a good share of the granules in the same pass, so the roof looks clean for a season and then ages faster than it ever would have with the moss left on.
The right method is slower and duller: take it off by hand with a brush and a scraper, working down the slope so you are not levering shingle edges upward, then treat what is left so the roots still in the mat die rather than regrowing over the winter. A zinc or copper strip near the ridge helps afterwards — rain picks up trace metal on its way down and keeps the slope hostile to regrowth.
Then clear the gutters, because all of it has ended up in there. If you would rather not spend a wet Saturday on a slippery roof, that is what we are for.
Talk to HJ Gomez Roofing
Tell us what the roof is doing. We will arrange a time to come and look, and tell you plainly what it needs.