Why Your Siding Has Black Streaks (and How Soft Washing Removes Them)
Drive through almost any neighborhood around Charlotte and you'll spot it: homes with dark streaks running down the siding, or black stains streaking the north-facing slope of a roof. Homeowners often assume it's dirt or "just age." Usually, it's something alive.
It's algae, not dirt
Those black streaks — especially on roofs — are commonly caused by a hardy blue-green algae. On siding and shaded walls you'll also find mildew and other organic growth. Because it's a living organism feeding on moisture (and, on roofs, on the limestone filler in shingles), it keeps coming back if you only rinse the surface.
Why our climate makes it worse
The Charlotte region's humid, warm seasons create ideal conditions for algae and mildew. The growth is almost always heaviest on:
- North- and east-facing walls that stay shaded and damp
- Areas under trees or near downspouts
- Roof slopes that get the least direct sun
Why a garden hose (or pure pressure) doesn't last
Spraying the streaks with water — even high pressure — knocks off the surface layer but leaves the organism behind, so it regrows within months. High pressure also risks damaging siding or roof shingles in the process.
How soft washing actually solves it
Soft washing applies a cleaning solution that breaks down the algae and mildew at the source, dwells briefly, then rinses at low pressure. Because it treats the growth rather than just the stain, results last far longer — and the gentle pressure protects your siding, paint, and roof.
What you can do between cleanings
- Trim back trees and shrubs to let walls dry and get sunlight
- Keep gutters and downspouts flowing so water doesn't sheet down walls
- Schedule periodic soft washing before growth gets heavy
The NOVA approach
NOVA's soft-wash process is designed to remove algae and mildew safely from siding and other delicate surfaces, with eco-friendly solution options and full insurance coverage.
Sources
Seeing streaks on your siding or roof? Contact NOVA or call (980) 266-4818 for a free soft-wash assessment.