Roof Cleaning: Pressure Washing, Soft Wash, or Leave It Alone?
Want a straight answer about your own roof?
Free inspection, written report, no sales pitch. We cover Johnson, Douglas, Wyandotte and Leavenworth counties.
If your roof has dark streaks running down it, you're not alone. That's Gloeocapsa magma, a type of blue-green algae that feeds on the limestone filler in asphalt shingles. It's incredibly common in the Midwest, especially on north-facing roof slopes that don't get as much direct sun. It looks bad, but here's the honest truth: it's mostly cosmetic. It's not eating through your roof. It's not going to cause a leak. But it does look terrible, and a lot of homeowners want it gone.
Pressure washing will damage your roof
This is the big one we want people to understand. A pressure washer puts out 2,000 to 3,000 or more PSI of water. That force can remove the granules that protect asphalt shingles from UV light and shorten the roof's useful life. Before cleaning, read the manufacturer's instructions and written warranty for the specific product. Do not assume a cleaning method is allowed across all shingle lines.
Soft washing is better, but not perfect
Soft washing uses low-pressure water combined with a chemical solution, usually sodium hypochlorite (basically pool bleach), to kill the algae. It's gentler on the shingles and it actually kills the organism instead of just blasting it off. If you're going to clean your roof, this is the method to use. That said, there are still risks. The chemicals can damage plants and landscaping below if not managed carefully, and whoever's up on the roof needs to know what they're doing to avoid overapplication.
Sometimes the best answer is to leave it alone. If your roof is within a few years of needing replacement anyway, spending $500+ on a cleaning doesn't make a lot of sense. And if the algae isn't severe, it's purely cosmetic, your roof is still doing its job. When it's time for a new roof, we can install shingles with algae-resistant granules (copper-infused) that slow the growth way down.
Not sure whether your roof needs cleaning, repair, or replacement? We'll take a look and give you the straight answer. Call us at (913) 954-4501.
Want a straight answer about your own roof?
Free inspection, written report, no sales pitch. We cover Johnson, Douglas, Wyandotte and Leavenworth counties.
