Best Ways to Clean Roof Streaks

LESLIE: Tim in Rhode Island is on the line with a question about how to clean roof streaks. How can we help you today?

TIM: I have a TPM and the front of the house is on the north side of the house. And the roof’s about 10 years old and now we seem to get these really black stripes on either side of the dormers. There’s actually three of them. It seems to be mold or something.

TOM: So, sometimes, you get plant deposits that will form mold or mildew or algae or lichen and kind of grow on those roofs and leave those sorts of roof streaks. The other thing that happens is sometimes, the hardware that’s in the roof where it releases some of its metals will actually clean pieces of the roof as the rain runs down and that can look very, very streaky. You see that frequently around the bottom of chimneys – like right underneath the chimney where it may have copper flashing, for example – and it’ll look streaky or cleaner under the chimney.

So, two things. Number one, there’s a product called Spray & Forget that’s designed to clean roofs and as the name implies, you basically just spray it and walk away. It takes a week or two to react with the sunlight but it’ll eventually kill off all of that plant growth that’s there.

Secondly, what you could do is if you can get up there – or you can have a roofer go up there – is if you add strips of copper up near the ridge vent, the same way I talked about the hardware that releases the metal, a piece of copper flashing 6 or 8 inches wide, all the way across the top, maybe under that top roof shingle, stick it down just a little bit.

TIM: OK.
TOM: As the rain hits that, it will release the copper and it’ll naturally wash your roof and stop that mold and mildew, algae or lichen from growing again causing roof streaks.

TIM: Hmm, OK. That’s Spray & Forget?