Clearing moss and debris from Vancouver, WA roofs

Moss is the most common roof problem in western Washington and Oregon. It grows fastest on north slopes, under tall firs and anywhere the roof stays damp for long stretches. As it thickens, moss lifts shingle edges, wicks water up under the laps and holds moisture against the roofing for months. Fir needles and debris pile up behind it, feeding more growth and blocking valleys and gutters.

Removing moss correctly matters as much as removing it at all. High-pressure washing strips granules off shingles and can force water under the laps, which shortens the life of the roof. Our crews remove moss by hand with brushes and plastic scrapers, use low-pressure rinsing only where it is safe, and apply a moss treatment that keeps killing roots for weeks after the visit.

Why moss is a roofing problem, not just a looks problem

Moss acts like a sponge on the roof. Each clump holds water against the shingles long after rain stops. On composite shingles that constant moisture breaks down the asphalt and loosens granules. As moss grows under shingle edges, it lifts them slightly, letting wind-driven rain slip underneath. On cedar shakes it softens the wood and speeds rot. On concrete tile it fills the gaps tiles use to drain and pushes water sideways.

Moss also drives other problems. Clumps break loose in rain and wash into gutters, where they block downspouts and cause overflows. Debris builds up in valleys and behind chimneys, building dams that hold water against flashing. Over time, a mossy roof leaks in places that seem unrelated to the moss itself, which makes the cause hard to trace. Clearing it early is far cheaper than repairing the damage it causes, and the roof dries faster afterward.

How our crews clean a roof

Our process is designed to remove moss without taking life out of the roof. We work from the top down so loosened moss falls away from clean areas, and we protect landscaping and siding below from debris and runoff. Treatment products are chosen for the roofing type, and we use the minimum needed to do the job. Our roofers wear soft-soled shoes and use roof anchors on steep slopes, so the cleaning itself does not damage shingles.

• Hand brushing and plastic-scraper removal
• Low-pressure rinse only where it is safe
• Moss treatment applied after cleaning
• Valleys and chimney backs cleared of debris
• Gutters and downspouts flushed afterward
• Photos of any damage found under the moss

Different roofs, different cleaning methods

Composite shingles need the gentlest approach. We brush and scrape moss off in the direction of the shingle laps so we do not lift tabs, and we avoid pressure washing entirely. Concrete tile and metal can take a light rinse in most cases, since the surface is harder, but tiles still need careful footing. Cedar shakes are often cleaned with brushes and a mild treatment, as aggressive scraping can thin already worn wood.

Lichen is different from moss. It grips the surface tightly and cannot be scraped off without damaging shingles. We treat lichen and let it die back over time, so it releases on its own with rain. Black streaks from algae are a third issue. They look bad but do less harm, and treatment can lighten them over a few months. We explain which growth is on your roof and what to expect from each.

What we find under the moss

Moss often hides damage. Once it is removed, we sometimes find cracked or lifted shingles, granule loss, nail pops or soft spots in the decking. Those are easier to repair right away than after another rainy season. We photograph any damage we uncover and give you a price for the repair. On roofs that are near the end of their life, we will tell you so, and suggest whether moss control or replacement makes more sense.