Portland Moss Severity Lookup
Identifies your address's canopy density tier (heavy / moderate / light) and recommends the appropriate cleaning chemistry, interval, and zinc strip strategy. Enter your Portland metro ZIP.
How aggressive is the moss pressure at your Portland address?
Portland metro neighborhoods fall into three canopy density tiers (heavy / moderate / light), each with different cleaning intervals and chemistry protocols. Enter your ZIP to identify your tier and the right cleaning approach.
Portland Moss Severity Questions
What do the canopy density tiers mean for Portland roof cleaning?
Three practical tiers. Heavy canopy (Forest Park orbit, Eastmoreland heritage core, Council Crest deep streets) sees moss colonization 50-100 percent faster than the metro average and needs 18-24 month cleaning intervals. Moderate canopy (most inner Portland and SE neighborhoods) is the standard 24-36 month interval. Light canopy (suburban Beaverton, Hillsboro, newer subdivisions) often stretches to 36-48 months between cleanings.
Why does canopy density matter so much?
Moss spores germinate in shaded, moist conditions. Sunny lots dry out between rain events fast enough to disrupt germination; canopied lots stay damp long enough that colonies establish in months instead of years. North-facing slopes specifically are the worst because they shed water but never see direct sun. Two homes a block apart can have meaningfully different moss pressure if one has mature Doug fir cover and the other doesn't.
What's the right cleaning protocol for my severity tier?
Heavy canopy needs soft wash plus zinc sulphate suppression at minimum, with zinc strip installation strongly recommended at the next cleaning to extend the interval. Moderate canopy benefits from soft wash plus suppression but can defer the strip install if budget is tight. Light canopy can often get away with chemistry-only soft wash on a 36-month interval without suppression. All three tiers share the rule: never pressure wash asphalt shingles.
Does this tool tell me how often to clean specifically?
Use this tool to understand your severity tier and the chemistry protocol. For the date-specific 'when should I clean next' recommendation that factors in your last cleaning year and zinc strip status, use the Cleaning Frequency Estimator. The two tools complement: severity says how aggressive the moss pressure is; frequency says when to act on it.
What if my ZIP is at a canopy boundary?
Some Portland ZIPs straddle the boundary between heavy and moderate canopy depending on which side of the street you're on. The tool reports based on dominant canopy in that ZIP; if your specific lot is unusually exposed (open south-facing slope, no nearby tall trees) or unusually shaded (deep in a stand of mature firs), shift one tier accordingly. A professional inspection during your next cleaning will calibrate further.