Long Island Roof Cleaning: A Complete Guide
Those black streaks running down the north side of your shingles are a live organism called Gloeocapsa magma. It eats the limestone filler in asphalt shingles. Left alone for 5+ years, it can shave 20 percent off a roof's lifespan.
Why Long Island roofs streak
LI's humidity, salt air, and tree cover create perfect Gloeocapsa conditions. The algae spores are airborne and colonize the shaded side of a roof first (almost always the north-facing slope). Once established, they spread spore-down across the whole roof.
Moss and lichen follow the algae. Both hold moisture against the shingles, accelerating granule loss and eventually lifting the shingle edges.
What the RCIA method is
The Roof Cleaning Institute of America recommends a no-pressure soft wash using a sodium hypochlorite solution. The chemistry kills the algae, moss, and lichen at the root. Natural rainfall over the following weeks rinses the dead organic matter off.
Pressure washing a shingle roof will void the manufacturer warranty (GAF, CertainTeed, and Owens Corning all explicitly prohibit it) and blow granules off the shingles. Any roofer who offers to pressure wash your shingles is either unlicensed or uninformed.
Typical pricing
2,000 to 2,500 sq ft roof: $550 to $825.
3,000+ sq ft roof or steep pitch: $800 to $1,250.
Add-ons: chimney flashing brightening ($75), skylight detail ($50 per skylight), plant saturation for runoff areas (included in every quote).
What a good roof cleaner does differently
Pre-soaks landscaping with clean water to buffer any runoff. Uses a downstream injector, not a direct pump, to keep pressure at the shingle under 500 PSI. Never walks the roof during application — a harnessed tech applies from ladders and ridge walks. Rinses the siding and gutters after the application to stop streaking. Leaves a 6-month warranty on visible results.