How do you choose roof stain removal contractors?
Why the method matters
The black streaks on Georgia roofs are mostly algae. High pressure water blasts granules off asphalt shingles, which shortens their life and can void the manufacturer's warranty. Shingle manufacturers and industry groups recommend a gentle wash instead, typically a diluted bleach based solution applied at low pressure and rinsed lightly.
Questions to ask a stain removal company
- What pressure do you use on shingles? The answer should be garden hose level, not a pressure wand.
- What is in your solution? Usually sodium hypochlorite with a surfactant. Ask about concentration.
- How do you protect plants? Pre wetting, covering, and rinsing landscaping afterward.
- Do you walk the roof? Foot traffic on hot shingles scuffs granules; good crews minimize it.
- Are you insured for liability and injuries to workers on your roof?
- What about gutters and downspouts? Runoff should be managed, not dumped into a flower bed.
How long it lasts
In shady, humid spots, streaks often start returning within a few years. Zinc or copper strips near the ridge slow regrowth below them, and algae resistant shingles are worth choosing at your next replacement. Our guide to black streaks and algae on roofs covers the biology, and moss and lichen on roofs covers the thicker growths.
When cleaning is not the answer
If shingles are bare of granules, curling or cracking under the stains, the stain is the least of the problem.