Pressure Washing vs Soft Washing a Roof: Which Is Right?
October 1, 2026 • Stampede Pressure Washing
The black streaks running down your roof are algae called Gloeocapsa magma. It feeds on the limestone filler in asphalt shingles. The question is how to remove it without ruining your roof. Here is the difference between pressure washing and soft washing a roof, and why the method matters.
What Pressure Washing a Roof Means
Pressure washing uses high pressure water to blast dirt and growth off a surface. On concrete that is fine. On a roof it is dangerous. High pressure can strip the protective granules off asphalt shingles, shorten the life of your roof, and force water under the shingles.
We do not use high pressure on roofs. It causes more damage than the algae ever would.
What Soft Washing a Roof Means
Soft washing uses low pressure, about the same as a garden hose, combined with a cleaning solution that kills mold, mildew, and algae at the root. The solution does the work, not the pressure. It removes the black streaks and keeps them from coming back as fast.
Soft wash is the safe, manufacturer approved method for cleaning asphalt shingle and metal roofs.
Which One Should You Use
Always soft wash a roof. Pressure washing is for concrete, driveways, and durable surfaces. If a contractor offers to pressure wash your roof with high pressure, that is a red flag. It can void your shingle warranty and lead to leaks.
Frequently Asked Questions
Will soft washing damage my landscaping?
We take care to protect plants and landscaping. The solution is rinsed and diluted, and we water nearby plants before and after the job.
How long does a roof soft wash last?
A proper soft wash kills the algae at the root, so results typically last one to two years depending on shade and humidity around your roof.
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