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
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.
tom @ www.Consolidated-Loans.info
Next time specify mildew or fungus resistant shingles. Only available in
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.
| 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 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.
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.
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