How to Get Rid of Moss on Your Roof in BC (And Keep It From Coming Back)
If you’ve noticed dark green patches creeping across your roof, you’re not alone. Moss is one of the most common problems BC homeowners deal with — and one of the most ignored until it’s too late. BC’s wet climate, overcast skies, and mild winters create basically perfect conditions for moss to take hold on asphalt shingles.
The good news is you don’t need to replace your roof or hire an expensive specialist. With the right approach you can clear it yourself and keep it gone.
Why BC Roofs Get Moss So Fast
Moss thrives in moisture and shade — two things BC has in abundance. Unlike drier parts of Canada where UV from the sun keeps roofs relatively clean, our overcast winters give moss months of ideal growing conditions. North-facing roof sections are almost always the worst affected since they get the least sunlight and stay damp the longest.
Asphalt shingles are particularly vulnerable because moss roots work their way under the shingle edges over time, lifting them slightly and allowing water to get underneath. Left long enough this leads to leaks, rot, and shingle damage that is genuinely expensive to fix.
What Not to Do
Before getting into the right method, it’s worth covering what a lot of homeowners get wrong.
Pressure washing a roof seems like the obvious solution but it’s one of the worst things you can do to asphalt shingles. The high pressure strips the granules off the surface of the shingle — those granules are what protect the asphalt underneath from UV damage and weathering. Pressure washing can take years off the life of your roof in a single afternoon.
You’ll see this debate all over contractor forums and the answer from anyone who actually works on roofs regularly is consistent — stay off the roof with a pressure washer.
The Right Way to Remove Moss from an Asphalt Shingle Roof
The method that works without damaging your shingles is straightforward:
What you’ll need:
- A stiff bristle brush with an extension handle
- Zinc powder or zinc sulfate granules
- A dry day with no rain forecast for 24-48 hours
Step 1 — Wait for a dry spell
Don’t attempt this on a wet roof. Wet shingles are slippery and dangerous, and moss is easier to remove when it has dried out slightly.
Step 2 — Brush from the peak downward
Using your stiff bristle brush, work from the peak of the roof downward in the direction the shingles lay. Never brush upward — this lifts the shingle edges and can cause damage. Work in sections and be thorough but not aggressive. You’re lifting and loosening the moss, not scrubbing the shingle itself.
Step 3 — Clear the debris
Once you’ve brushed a section, let the loosened moss fall clear. Don’t leave clumps sitting on the roof or in the gutters — clean them out so water can drain properly afterward.
Step 4 — Apply zinc powder along the peaks
This is the step most DIY guides leave out entirely. Once the moss is cleared, apply zinc powder along the ridge line at the peak of the roof. When it rains — and in BC it will rain — the zinc washes slowly down the roof surface creating an environment where moss simply can’t establish itself.
Zinc is the reason you’ll notice that roofs with metal flashing around chimneys and vents tend to stay cleaner directly below those metal strips. The same principle applied deliberately along the peak protects the whole roof.
How Long Does It Last?
Applied properly, zinc powder treatment can keep moss at bay for 1-2 years depending on how much rainfall you get and how much tree cover is over your roof. North-facing roofs in heavily treed areas may need reapplication annually. A more exposed south-facing roof might go longer between treatments.
The key is not waiting until you have a full moss problem before reapplying. A light annual maintenance brush and zinc reapplication in late summer — before the wet season hits — is far easier than dealing with a roof that’s been growing moss for three years.
When to Call a Professional
If your moss coverage is extensive, the roof is steep, or you’re not comfortable working at height — call someone. A roof fall is not worth the cost of a professional clean. A reputable exterior contractor in BC will use exactly this method and can get it done safely in a few hours.
If you’re in the Nanaimo area or anywhere on Vancouver Island, this type of service typically runs $200-400 depending on roof size and how long the moss has been left.
The Bottom Line
Moss on a BC roof is inevitable — but damage from moss is not. A stiff brush, some zinc powder along the peaks, and an annual check before the rainy season is all it takes to keep your asphalt shingles in good shape for years. Skip the pressure washer, work downward, and let the zinc do the long term work.
BCExterior.ca 
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