Black roof stains

[Slingah]

One or more sections of the roof covering appear stained. An algae known as Gloeocapsa Magma is the most likely culprit and this algae affects nearly 80 percent of the homes across the United States. Gloeocapsa Magma is a species of algae that causes black streaking and discoloration on asphalt/fiberglass shingles. The black staining you see on many roofs is caused by the life cycle of algae and fungus spores that land on houses via wind or wildlife. While this algae can grow just about anywhere, it prefers humid environments. A preferred food source of this algae is limestone which is used as "filler material" by most shingle manufactures. Higher quality shingles are manufactured with preventative measures such as copper or zinc containing granules. Several methods exist to prevent and clean infected areas. Installing zinc or copper strips near the roof ridge can prevent further algae growth.

Take a photo Paul and post it. Forget that stuff you used. Trust me the only way to rid of it is strong bleach and a surfactant.
Posted from my iPhone/Mobile device

[FormerUser]

I'm old school.If you have an asphalt roof I would say go with Jomax and bleach(as per instructions).Pre-soak any bushes/wood siding with copious amounts of water and spray the solution on the roof and then rinse from the top down.Post soak your shrubs/wood and you should be all set.If you have algae/moss you might have to do some scrubbing but not to much as you don't want to scrub the granules off.

[FormerUser]

Originally Posted by Slingah

Take a photo Paul and post it. Forget that stuff you used. Trust me the only way to rid of it is strong bleach and a surfactant.
Posted from my iPhone/Mobile device

Or what Slingah said.To which I'm sure he would agree Jomax and bleach.

[PaulS]

The 1st. picture is over the garage and you can see some yellowish moss along with the black mildew. The garage is a detached and unheated. The roof actually looks better now that I think of it. I should have taken pictures b/f I started

[Slingah]

Use bleach or liquid pool shock(sodium hypochlorite) and T.S.P. or Jomax in a pump up sprayer.
Wet roof FIRST and all surrounding plants, bushes, grass etc. with plain water...then apply mix to roof. Let the chemical do the work. Sometimes a second application is needed.
Don't be afraid of the bleach....it will NOT hurt asphalt shingles and is the ONLY thing that will work.

bleach is 6% sodium hypoclorite
liquid pool shock is about 12% sodium hypoclorite
I buy pool shock at Ocean State Job Lot to do all my exterior cleaning.

http://www.squidoo.com/roof-cleaning...-black-streaks