Black algae streaks
The dark vertical staining on asphalt shingles killed at the root, not just rinsed.
Those black streaks running down a roof are a blue-green algae that feeds on the limestone filler in asphalt shingles. It is not just cosmetic — as it spreads it holds moisture against the shingles and works under them, and left for years it shortens the life of the roof. In St. Louis, shaded and heavily treed lots grow it fastest.
A roof is the last surface that should ever see high pressure. We soft wash it: no pressure at all, just a cleaning solution applied low and rinsed gently, which kills the algae and moss at the root. The streaks lift, the color evens out, and because the growth is killed rather than knocked loose it stays clear far longer than a pressure rinse would.
This is also the safest way to protect a roof you are not ready to replace. Clearing the algae removes what holds moisture against the shingles, and a soft wash costs a fraction of a new roof.
What's included
The dark vertical staining on asphalt shingles killed at the root, not just rinsed.
Growth in shaded valleys and north slopes cleared without lifting shingles.
A true soft wash — zero pressure on the roof surface, so nothing gets damaged.
The black tiger-striping on gutter faces cleaned while we are up there.
Landscaping below the roofline pre-wet and rinsed so runoff does no harm.
Removing the algae removes what holds moisture against your shingles.
Good to know
Yes — it is the method roofing manufacturers recommend. There is no pressure on the roof at all. The cleaning solution does the work, not force.
A pressure rinse only knocks the surface growth loose. Soft washing kills the algae at the root, so it takes far longer to return.
We minimize roof contact and work from ladders and the ground wherever possible, applying and rinsing the solution without pounding the shingles.
Free estimate
Local, insured, and honest about what your property needs. We come out, look at the actual job, and give you a firm quote — no pressure.
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Roof Soft Washing across St. Louis