Moss doesn’t come off a roof cleanly. It grips the surface and works under shingle edges, so scraping it or blasting it off takes granules and shingle edges along with it. We use a low-pressure soft wash instead, which is slower and leaves your roof with its service life intact.
If your insurance company has told you the moss needs removing, say so on the form. We can provide written confirmation as a licensed roofing contractor that the roof has been cleaned, which is usually what they’re asking for.
Moss, algae, or lichen?
Moss is a plant. It holds water like a sponge and grips the roof, and as it thickens it lifts the lower edges of shingles and tiles. That lift is the real problem, because it gives wind-driven rain a way underneath. Moss is the one worth acting on.
Algae is the dark streaking you see running down slopes, usually worst on the shaded side. It’s largely cosmetic and it doesn’t lift anything, though it does hold moisture and it makes a roof look years older than it is.
Lichen is an algae and a fungus living together, and it bonds to the surface far more tightly than moss does. It’s the hardest of the three to deal with without damaging what’s underneath.
Which one you have changes what we’d recommend, which is why the form asks what it looks like rather than what it’s called.
What moss actually does
Moss grows where a roof stays damp: north-facing slopes, valleys, under overhanging branches, along the shaded side of a ridge. It doesn’t need soil, just moisture and a surface to hold onto. Same organism, three different failure modes, which is why the form asks what your roof is made of.
As it thickens it does three things. It holds water against the roofing material long after the rain has stopped. It lifts shingle and tile edges, opening a path for wind-driven rain. And it blocks drainage where it collects, so water sits in valleys and behind penetrations rather than running off.
On wood shake the constant moisture is the main issue. On composition it’s the lifting. On tile it’s usually the drainage. Same organism, three different failure modes, which is why the roof material matters when you describe it.
If your insurer has asked for it
Insurance companies increasingly ask homeowners to have moss removed as a condition of renewal, and a photograph of a clean roof isn’t always what satisfies them.
Tell us on the form if that’s your situation. The service can include written confirmation from ACS Roofing, as a licensed contractor, that the roof has been cleaned, which is generally what the insurer wants on file.
How we clean it
Low-pressure methods designed to protect roofing materials are used. The roof material, pitch, access, and surrounding environment are all taken into account.
Scraping moss off dry, or blasting it with a pressure washer, takes the shingle’s mineral granules with it and lifts edges that were already loose. It looks decisive and it costs the roof years.
Keeping it from coming back
Moss returns because the conditions that grew it are still there, and two of those you can change yourself.
Trimming branches back off the roof lets more sun onto the slope and lets it dry between rains. It’s the single most effective thing a homeowner can do and it costs nothing but a tree service.
Clearing debris helps for the same reason. Leaves and needles hold moisture and give moss somewhere to establish, which is why moss and debris tend to show up together.
Cleaning or moss removal?
Both use the same low-pressure soft-wash process, so it’s a question of what you’re after rather than two different treatments.
Use this form if you know moss is the issue, or if your insurer has asked for it.
Use the Roof Cleaning form if you’re after a general clean: dirt, debris, organic growth and the overall appearance of the roof.
If you’ve seen staining on a ceiling, damp in the attic, or water during a storm, a Leak/Repair Evaluation comes first. Moss on a roof that’s already leaking is worth noting, but it isn’t the thing to fix first.
If you’re buying, selling, or in escrow, a Premium Roof Inspection produces the written report those transactions call for.
What happens after you submit
- We review what you’ve described and contact you to confirm an appointment window.
- A nationally certified inspector evaluates the roof before we recommend any work.
- You receive a written report with high-resolution digital photos and a proposal with our recommended next steps, sent digitally within a few business days.
Those next steps sometimes include repairs that need doing before the roof is cleaned rather than after. If that’s the case with yours, the report will say so.
What it costs
Moss removal is quoted per property, since it depends on how much there is, the roof material and the access.
You receive a written proposal setting out the work and the cost before anything is scheduled, and nothing goes ahead until you’ve agreed to it.
Before we arrive
We prefer you to be there if you can, but we can carry out the work as long as we have access to the perimeter of the home.
What helps: side gates unlocked, dogs secured, vehicles clear of the driveway, and windows closed on the day.
Who’s looking at your roof
The reason to have a roofer assess moss rather than a cleaning service is that the decision isn’t really about the moss. It’s about what the roof underneath can take, and how much service life it has left to protect. Our inspectors are HAAG Certified and nationally certified in the Tile Roofing Industry. ACS Roofing has worked the Sacramento area since 1989, is BBB Accredited with an A+ rating, and was a 2025 Nextdoor Neighborhood Favorite.