Does removing roof stains with vinegar work?
Short answer. Vinegar is not a good choice for roof stains. Household vinegar is a weak acid that may kill some surface growth on contact but does little to the algae colonies behind black streaks on shingles, and it can harm plants and be hard on metal flashing and gutters. Shingle manufacturers generally point to diluted bleach solutions or approved roof cleaners instead.
Why vinegar falls short on roofs
- Strength: kitchen vinegar is only a few percent acetic acid. It can burn the tops of small plants but rarely penetrates established algae or moss.
- Coverage: roofs are large, and the gallons needed make it impractical.
- Stronger vinegar is hazardous: horticultural vinegars with much higher acid content can burn skin and eyes and are not labeled for roofs.
- Metal: acids can etch or discolor some metals, including galvanized and aluminum parts.
- Warranty: the asphalt roofing industry's guidance is not to use chemicals the shingle manufacturer has not approved.
Match the stain to the right fix
- Black or dark streaks: algae. A diluted bleach solution, applied gently, lightens them.
- Green cushions: moss. Use a moss treatment labeled for shingles, then brush the dead moss downhill.
- Gray-green crusty patches: lichen. Treat and let it weather off rather than scraping.
- Orange or brown streaks: often rust from metal vents, flashing, or fasteners. Find the rusting part.
- Shiny black spots or drips: tar or roofing cement, usually from old repairs.
One important warning
Never mix vinegar with bleach. The combination releases chlorine gas.
For safer approaches, see black streaks and algae on roofs and moss and lichen on roofs.