Most people see moss on a roof and think it's an aesthetic thing. Something to get to eventually. The reality is that moss holds moisture against your shingles. For months at a time. In a climate like the Fraser Valley's, where we get rain from October through April, that moisture never fully dries out. It sits there, working its way under the shingles, lifting them off the substrate.
Once moss gets under your shingles, it starts to separate them from the roof deck. That separation lets water in. And once water gets in, you're no longer looking at a cleaning problem. You're looking at rot, mould inside the attic, and eventually a structural issue. A cleaning that would have cost a few hundred dollars becomes a roofing job that costs several thousand.
There's also the warranty issue. Most shingle manufacturers have moisture and moss clauses in their warranties. If a roofing contractor inspects your roof after damage and finds evidence of prolonged moss growth, your warranty may not cover the repair. This is not a hypothetical. It happens regularly. The manufacturer's position is that moss is a maintenance issue, and you failed to maintain.
Most homeowners in Abbotsford don't notice the moss until a neighbour mentions it, or until they're up on a ladder for something else.
Get a free quote→The right solution is soft washing, using low-pressure water with a biodegradable cleaning solution. High-pressure washing on a roof strips the granules off asphalt shingles, which shortens their life significantly. Any cleaner who shows up with a standard pressure washer and points it at your shingles is doing it wrong. Make sure you ask about their method before they start.
If you can see the moss from the street, it's already been there long enough to cause early damage. If you can't see it but haven't had the roof cleaned in three or four years, it's worth a look. In the Fraser Valley, moss establishes itself faster than most people expect. One wet winter is all it needs.
