My roof (only 6 years old) has black streaks running down it. What is causing these? My previous roof had the same stains, and I had the roof replaced. These are supposed to be 20yr shingles.
Does anyone know what is going on?
Middle Ohio homeowner
the black streaks are algae. they do not hurt the shingles but can be unsightly. zinc (in the form of galvanized metal) inhibits the growth of the algai--for this reason you might notice unstained sections downslope from galvanized flashings. they sell galvanized strips which can be tucked under the ridge cap and prevent this staining. not sure if there is any way to get rid of the stains once there...maybe someone else does.
IMHO:
Since they are vertical, it sounds like mildew. Let me guess, it's on the side that gets the least amount of sun.
Now once you verify this is what you have, might want to determine what you want to do after this.
later,
tom @
Stop tossing your underwear up there!!!
: P
Next time specify mildew or fungus resistant shingles. Only available in some colors.
I just had a company in Raleigh, NC called Mildew Magic wash my house. They do roofs too but I didn't need that done. I don't know if they are a national company but you might want to check for them in your phone book. They did a nice job on the house overall.
The streaks are algae. I've read that this algae (which feeds on a component of the shingles) can cause premature granule loss, and considerably shorten the life of a roof.
To get rid of the algae, you can ever-so-gently spray (that is, do NOT use pressure) the roof with a solution intended for this purpose (check out the big box stores near you) or a solution of water and chlorox. Unfortunately, the streaks will eventually come back.
On Thu, 07 Dec 2006 17:26:45 -0600, "MiddleO" wrotF:
Algae probably, but possibly tannin from clumps of leaves that collect on the roof and then the rain water dissolves the tannin and it streaks down. You see that same effect on concrete sidewalks in the fall after leaves have been rained on and then blown away.
Since Santa Claus had his heart attack, Bubba Claus has been doing the deliveries. He uses an ATV and carries a gun rack and eats moon pies. Not much you can do about it.
It is mold or mildew. There are shingles that contain metal bits to prevent this. I recommend staying off your roof (and not cleaning it) to make it last as long as possible.
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