Controlling algae, mildew and mold growth outdoors is very hard. Skip to content. All Sections. Subscribe Now. 63°F. Monday, June 16th 2025 eNewspaper. Home Page. Subscriber Services.

Mold: Relatively rare on roofs, but when it does appear, it’s likely the result of algae left on the roof too long, which makes the shingles perpetually damp, and a good home for mold.

With infrequent use, the algae, mold and bacteria can build up. When the jets are turned on, some of the buildup is knocked loose and it floats around in the water, appearing as black specks.

‘Mold, algae’: Insurer drops SF homeowners, citing aerial footage of roof that didn’t exist. By CNN. Published December 12, 2024 12:13 PM . KGO. By Stephanie Sierra. Click here ...

For algae, mold, and mildew to thrive, they just need three things — and sometimes just two! Typically, some algae, mold and mildew need: the spores, food and water.