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What to do with black streaks on roof.
Posted on 9/16/25 at 11:26 am
Posted on 9/16/25 at 11:26 am
My roof is about 9 years old. Still in good shape but it's getting that black stuff starting to build up. I've seen people say it's good to soft wash it because the algae or whatever it is will damage the shingles over time and I've seen people say you damage it more by trying to clean it.
I'm leaning toward going the soft wash route but wanted to see what you intelligent gentlemen of the Home & Garden Board had to say about it.
I'm leaning toward going the soft wash route but wanted to see what you intelligent gentlemen of the Home & Garden Board had to say about it.
Posted on 9/16/25 at 11:32 am to OysterPoBoy
Soft washing a roof generally does not void the warranty if it is done according to the manufacturer's guidelines. Many roofing manufacturers specifically allow or recommend soft washing (which uses low pressure and specialized cleaning solutions) as a safe cleaning method. However, using high-pressure washing or unsafe chemicals contrary to the warranty guidelines can void the warranty. It is important for homeowners to carefully read their roof warranty documents and follow the recommended cleaning methods to avoid voiding the warranty, and hiring professionals familiar with warranty requirements can help ensure compliance.
LINK
LINK
Posted on 9/16/25 at 5:55 pm to OysterPoBoy
My house faces north. I’ve had it done twice by the same guy. My roof is too tall, and too steep for me to safely reach portions of it, myself. He charged me $275 each time. Excellent results.
Posted on 9/16/25 at 7:38 pm to OysterPoBoy
It's a fungus.
Yes, the zinc in galvanized roofing can help inhibit and kill fungus, algae, and moss. The effect comes from the metal's fungicidal properties, which are released and carried down the roof by rainwater.
How zinc on a galvanized roof kills fungus
Releases zinc ions: Galvanized steel is coated with a layer of zinc to protect it from corrosion. When it rains, trace amounts of zinc are washed off the metal as zinc carbonate.
Inhibits growth: The zinc ions carried by the rainwater create an environment toxic to moss, algae, and fungus, preventing new growth from taking hold.
Gradual removal: Over time, the moss and other growths already on the roof will wither, die, and fall off. The effectiveness of the zinc diminishes further down the roof, so larger roofs may require multiple strips to be fully effective.
Yes, the zinc in galvanized roofing can help inhibit and kill fungus, algae, and moss. The effect comes from the metal's fungicidal properties, which are released and carried down the roof by rainwater.
How zinc on a galvanized roof kills fungus
Releases zinc ions: Galvanized steel is coated with a layer of zinc to protect it from corrosion. When it rains, trace amounts of zinc are washed off the metal as zinc carbonate.
Inhibits growth: The zinc ions carried by the rainwater create an environment toxic to moss, algae, and fungus, preventing new growth from taking hold.
Gradual removal: Over time, the moss and other growths already on the roof will wither, die, and fall off. The effectiveness of the zinc diminishes further down the roof, so larger roofs may require multiple strips to be fully effective.
Posted on 9/16/25 at 9:24 pm to OysterPoBoy
I don’t know any soft wash guys that don’t use bleach. And I don’t know a shingle that won’t void warranty. There are specific zinc cleaners that will get it looking nice. Shingle shield is the product I always use. There are also zinc strips that you can tuck under your shingle to keep clean if you don’t mind looking at them. I wouldn’t put them on the front side of my house.
Posted on 9/17/25 at 9:05 am to Art Vandelay
Those zinc strips really look like shite but they are affective. Next time you look at a roof darkened by fungal growth (most obvious on the north facing slopes) you'll see the shingles are usually much cleaner below galvanized roof vents or galvanized flashing.
There are soft wash options that won't void your warranty but the fungal growth will eventually return faster than you think. It does make the roof look much better though. Here are the roof cleaning instructions from CertainTeed.
There are soft wash options that won't void your warranty but the fungal growth will eventually return faster than you think. It does make the roof look much better though. Here are the roof cleaning instructions from CertainTeed.
Posted on 9/17/25 at 9:13 pm to Cage Fighter Trainee
quote:
There are soft wash options that won't void your warranty but the fungal growth will eventually return faster than you think. It does make the roof look much better though. Here are the roof cleaning instructions from CertainTeed
Been out the game for a few years now. But I sold Certainteed for a long time. I’m surprised they revised their warranty. Sure enough there is nothing about not using bleach on your shingles. It used to be something in the warranty about cleaning with chemicals. I guess they can still get you with “damage from any cause other than inherent manufacturing defects”. Honestly after about 10 years it really doesn’t matter.
Also side note, I saw a house that patched a roof and they must have used some type of streak fighter shingle. They must put zinc in the shingle now because not only is the patch clean but it streaked clean spots down the roof.
Posted on 9/18/25 at 10:16 am to couv1217
quote:yeah I googled it after I posted. It works but don’t use it to patch your roof.
It’s cooper
Posted on 9/19/25 at 5:23 am to Art Vandelay
Atlas introduced scotch Guard back in I think 2011or 12, it was a marketing ploy, the difference was more Atlas increased the Zinc content in the shingle which prevented the algae, fungus growth, that's the only shingles I sold
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