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Question DetailsAsked on 10/14/2014

How do I remove black streaks from roofing shingles

Green Asphalt shingles. Roof is about 7-8 years old

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Depends on what they are from - if leaching of asphaltic (or wood in caseof wood shingles) oils or staining due to the action of metal (usually copper) moss-prevention granules on the shingles, not much you can do. Some people do bleach stains like this out, but that really damages the shingles and shortens their useful life, and will void the warranty. If due to rusting of shingle staples/nails (let's hear it for Chinese "galvanized" and other protective coated fasteners that rust in weeks) nothing you can do short of removing all the shingles and reinstalling with quality fasteners.
If due to the granules coming off and exposing the asphalt underneath, unless you got the absolute cheapest shingloes on the market (5 or 10 year warranty) then they are prematurely failing, though depending on how badly they are losing their granules it is upto you whether you file a warranty claim, because usually you have to pay allthe labor - the manufacturer only replaces the defective shingles.If the streaks are moss or lichen growing on the roof, then Lilly Moss Out or similar zinc powder product scattered over it will kill most types off - though I have found on my roof there is one orange/tan lichen type inour area which actually thrives on the Moss Out and the leached zinc downhill of flashing and galvanized roof jacks around pipes and such. I have even found that type growing on galvanized fence posts and rails, so it REALLY likes zinc. Let sit for a couple months, and if still pronounced streaks then hose and lightly (so as to not remove many roof granules) scrub brush it off, then recoat with moss killer as a preventative. Be aware concentrated runoff of this treatment will damage or kill ornamentals and bulbs in the immediate runout area, though it does nothing noticeable that I have ever seen to mature trees or to lawn. And of course do not discharge into garden patches used to grow food.

Answered 6 years ago by LCD

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