What would cause this on roof--mold?
Maybe it's this algae:
http://www.todayshomeowner.com/remove-prevent-algae-stains-asphalt-shingle/
This happens all the time on shady parts of the roof. You can have the roof cleaned (about $500) if it bothers you, but it's not harming anything.
A realtor may suggest you clean the roof before putting the house on the market, but I doubt it's a big deal in a market like M/SO.
Nothing to get worried about, although it is a bit unsightly. As others have said, it can be cleaned, but it is not going to hurt anything.
if you're not afraid of heights , go up there with a pump sprayer filled with household bleach. Spray, let it sit for a few, hose down with water.
dano said:
if you're not afraid of heights , go up there with a pump sprayer filled with household bleach. Spray, let it sit for a few, hose down with water.
diluted household bleach
There are products at Home Depot you can hook up to your garden hose that you spray on and leave alone. Not sure if they work or not. You can also use a pressure washer to get up there without having to climb.
I would advise against using a pressure washer from below. One would be likely to get water under the shingles, and thus, create a leak, or mold problem.
TomR
unless you are experienced I wouldn't recommend a pressure washer from above, either. If it is mishandled it can out some serious wear on the shingles.
We used a pressure washer to spray down the roof of the house we sold a couple of months ago. The idea is NOT to apply pressure, but rather to get the solution up that high. You aim the stream above the shingles so the solution lands on the roof. The pressure is not applied directly to the roofing.
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Ever seen this? I know-- we do need to reroof. But I'm wondering if it's ultra urgent due to this bizarre black streaking, which only appears on the back side of our house. Could it be from concealed mold from prior over roofing? Or worse, mold concealed behind finished areas in the attic? Thoughts? My daughter's room is under most streaked part, and she has always suffered from the most from allergies.
Thanks in advance.