If you live in the Lower Mainland, you have probably seen it: green, spongy moss creeping across roofs every winter. Our mild, wet climate is perfect for moss, and while it can look harmless, it is one of the most common causes of early roof wear in BC. This guide explains why moss is a problem, how to remove it safely, and how to keep it from coming back.
Why Moss Is Bad for Your Roof
Moss acts like a sponge. It holds water against your roof for days or weeks after the rain stops, and that constant moisture causes damage over time:
- It lifts shingles. Moss grows into the gaps between shingles and pushes them up, letting wind-driven rain get underneath.
- It speeds up decay. Trapped moisture breaks down asphalt shingles and rots cedar shakes and roof decking.
- It blocks drainage. Moss and debris wash into gutters and valleys, causing overflows and leaks.
- It shortens your roof’s life. A roof left covered in moss can wear out years earlier than one that is kept clean.
Why Moss Grows So Well in the Lower Mainland
Moss thrives where it is damp, shady and mild, which describes much of the Lower Mainland from October to April. North-facing roof slopes, roofs under tall trees, and homes on the North Shore, in Burnaby and in the Tri-Cities tend to see the heaviest growth. Older roofs with rough, worn surfaces also give moss more places to take hold.
How to Remove Moss From Your Roof Safely
Safety first: wet, mossy roofs are extremely slippery. If your roof is steep, high or you are not comfortable working at heights, leave this job to professionals.
- Brush, don’t blast. Gently remove loose moss with a soft brush, working from the top of the roof downward so you don’t lift shingles.
- Apply a roof-safe moss treatment. Use a product designed for roofs, follow the label, and protect plants, lawns and nearby water from runoff.
- Let it work. Many treatments kill the remaining moss over several weeks, after which it loosens and washes away with the rain.
- Clean your gutters. Clear out moss and debris so water can drain freely.
Avoid pressure washing. High-pressure water strips the protective granules off asphalt shingles, damages cedar, and can force water under the roofing. It often does more harm than the moss itself.
How to Prevent Moss From Coming Back
- Trim overhanging trees to let in more sunlight and reduce falling debris.
- Keep the roof and gutters clear of leaves and needles, especially in fall.
- Install zinc or copper strips near the ridge. When it rains, they release minerals that help discourage moss growth.
- Book regular inspections. A professional roof inspection twice a year catches moss and the damage it causes early.
- Consider moss-resistant materials. If you are replacing your roof, algae-resistant shingles or metal roofing are far less welcoming to moss.
When Moss Means It’s Time for Repair or Replacement
If moss has been left for years, there may be damage underneath: lifted or curled shingles, soft spots, rotted decking or leaks inside your home. In that case, removing the moss is only the first step. Our team can assess the roof and recommend targeted roof repair or, if the roof is near the end of its life, a full roof replacement.
Get Help With Roof Moss
Great West Roof helps homeowners and strata properties across the Lower Mainland deal with moss and the damage it leaves behind. For a free assessment, contact us or call (778) 578-7018.