Dark streaks on shingles - are they worn out?

    The roof of my house has many vertical "streaks" in the asphalt shingles, evidently caused by the removal of the light-colored granular material from the shingles which exposes the darker matrix. The streaks start in a small region then spread downward and outward for about a foot - sort of like the splat of a juicy insect against a windshield. Much of the granular material ends up in the gutters. This has mostly occurred within the last year.
    Is this normal wear-and-tear, or an indication that the shingles are overly worn? The re-roof job is about 10 years old. None of the other houses in the neighborhood show this, but ours is the only light-colored roof. Otherwise everything is fine - no cracks, loose shingles or leaks. We live in Marland, weather/sun not too extreme...
I greatly appreciate any advice,
Mike
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Might be mildew. There are sprays, or you could put a strip of zinc near the ridge. TB
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it is only a cosmetic problem at this point
it will be a "genuine" problem at the first sign of a leak
at the first sign of a leak, replace roof, as it will get worse in a hurry
but you are fine for now

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This is often an indication that the shingles are getting hard and brittle. If it's just spots and streaks, but otherwise the roof looks OK, I wouldn't worry about it just yet.
But I also wouldn't suggest waiting for signs of actual leakage to replace the roof -- that can end up with an emergency re-roof in nasty winter weather, or a homeowners insurance claim for lots of water damage. When the aggregate loss gets more widespread, or the shingles start curling up at the corners, I'd go for a planned re- roof before it's an emergency.
Also, if the existing roof is failing well before its planned life, I'd check on ventilation -- is the roof getting too hot, shortening the shingles' life?
--
snipped-for-privacy@phred.org is Joshua Putnam
<http://www.phred.org/~josh/
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Thank you all very much for your suggestions!
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