Those dark roof streaks aren’t just dirt—they’re usually Gloeocapsa magma, an algae that thrives on humid, shaded shingles. Blasting it with high pressure can void warranties and damage granules. The safe method is a manufacturer-recommended soft wash treatment that neutralizes organic growth and restores shingle color.
Why it matters: Algae holds moisture and can shorten shingle life. A soft wash uses targeted detergents at low pressure to treat the staining, then a gentle rinse. Some residue lightens further with a few rains as the neutralized growth dislodges.
Preventing regrowth: Overhanging branches, poor attic ventilation, and north-facing roof planes invite algae. Trim trees where possible and consider zinc or copper strips near the ridge to inhibit future growth.
Safety first: Trained technicians use roof-rated footwear, anchor points, and, when needed, apply from the ground using extended systems. Overspray control and plant protection (pre-wet/rinse) are built into the process.
When to clean: Early summer or early fall—when temps are moderate—helps chemistry work efficiently and reduces heat exposure for crews.
Get rid of black streaks without damaging your roof. Call 262-525-8327 for a Delafield roof soft-wash evaluation and quote.
