I have an white asphalt roof that has several black algae streaks. As a
test I sprayed 1 with a mixture of bleach and Jomax House Cleaner. The
stain came off but it took repeated sprayings of the solution (per the
Jomax label). I used Jomax House Cleaner because I did not know there
was a Jomax Roof Cleaner and my local HDW store only stocks the house
cleaner. It is probably the same product.

For convenience, does anyone know of a sprayer that I connect to my
garden hose? I was thinking of a garden sprayer like they sell to spray
Ortho chemicals onto trees. But what setting would I set the sprayer to
adjust the concentrate of the Jomax/Bleach mix?

higgledy wrote:
I have an white asphalt roof that has several black algae streaks. As a
test I sprayed 1 with a mixture of bleach and Jomax House Cleaner. The
stain came off but it took repeated sprayings of the solution (per the
Jomax label). I used Jomax House Cleaner because I did not know there
was a Jomax Roof Cleaner and my local HDW store only stocks the house
cleaner. It is probably the same product.

For convenience, does anyone know of a sprayer that I connect to my
garden hose? I was thinking of a garden sprayer like they sell to spray
Ortho chemicals onto trees. But what setting would I set the sprayer to
adjust the concentrate of the Jomax/Bleach mix?


I hope you have better luck than I did. I used a tank sprayer to soak
the shingles with a mixture of Jomax and Bleach. After it had set a
while, I used a pressure washer on a low setting to clean the shingles.
(You can damage the shingles if you use too much pressure.) It
cleaned them, but when I noticed that every house around me had the same
problem I did, I said this is a losing proposition. I believe the
fungus would simply start again from airborne means.

It could easily become a career choice, and not one I would want.

Ken,

You are correct that it will only start again but I need to replace a
few shingles anyway. While I am up there I am thinking about installing
zinc or copper flashing near the top to act as a algaecide. I need to
check on pricing of the flashing to see if it is not crazyily
expensive. My house is only 10 years old, the builder put the cheapest
shigle possible even though the neighborhood is built on a windy ridge.
What an f'er. Anyway, I cannot afford a $10k new roof right now so I
need to do what I can to make my house look decent. It is a rancher
with a white-tall pitched roof. The streaks make the whole look like
trash.


Ken wrote:
higgledy wrote:
I have an white asphalt roof that has several black algae streaks. As a
test I sprayed 1 with a mixture of bleach and Jomax House Cleaner. The
stain came off but it took repeated sprayings of the solution (per the
Jomax label). I used Jomax House Cleaner because I did not know there
was a Jomax Roof Cleaner and my local HDW store only stocks the house
cleaner. It is probably the same product.

For convenience, does anyone know of a sprayer that I connect to my
garden hose? I was thinking of a garden sprayer like they sell to spray
Ortho chemicals onto trees. But what setting would I set the sprayer to
adjust the concentrate of the Jomax/Bleach mix?


I hope you have better luck than I did. I used a tank sprayer to soak
the shingles with a mixture of Jomax and Bleach. After it had set a
while, I used a pressure washer on a low setting to clean the shingles.
(You can damage the shingles if you use too much pressure.) It
cleaned them, but when I noticed that every house around me had the same
problem I did, I said this is a losing proposition. I believe the
fungus would simply start again from airborne means.

It could easily become a career choice, and not one I would want.

try pure full strength bleach

higgledy wrote:
Ken,

You are correct that it will only start again but I need to replace a
few shingles anyway. While I am up there I am thinking about installing
zinc or copper flashing near the top to act as a algaecide. I need to
check on pricing of the flashing to see if it is not crazyily
expensive. My house is only 10 years old, the builder put the cheapest
shigle possible even though the neighborhood is built on a windy ridge.
What an f'er. Anyway, I cannot afford a $10k new roof right now so I
need to do what I can to make my house look decent. It is a rancher
with a white-tall pitched roof. The streaks make the whole look like
trash.

For what it is worth, I originally had black shingles on my house and
replaced them with lighter colored ones so as to reflect some sunlight
on the roof. When I replace the shingles the next time I am going with
a dark shingle in order to minimize the impact of the stains.

One other comment: A couple of the homes in my area (Mid-south)
attempted to stop such problems with the zinc strips after re-roofing
their homes. From my observation their attempt was not successful. It
might have had some impact, but they did not rid their roofs of the stains.

If someone ever invented a shingle that would prevent such stains from
developing, he would be a very rich man. I know there are some that
claim some success, but I do not think any work 100%.


Ken wrote:
higgledy wrote:
I have an white asphalt roof that has several black algae streaks. As a
test I sprayed 1 with a mixture of bleach and Jomax House Cleaner. The
stain came off but it took repeated sprayings of the solution (per the
Jomax label). I used Jomax House Cleaner because I did not know there
was a Jomax Roof Cleaner and my local HDW store only stocks the house
cleaner. It is probably the same product.

For convenience, does anyone know of a sprayer that I connect to my
garden hose? I was thinking of a garden sprayer like they sell to spray
Ortho chemicals onto trees. But what setting would I set the sprayer to
adjust the concentrate of the Jomax/Bleach mix?

I hope you have better luck than I did. I used a tank sprayer to soak
the shingles with a mixture of Jomax and Bleach. After it had set a
while, I used a pressure washer on a low setting to clean the shingles.
(You can damage the shingles if you use too much pressure.) It
cleaned them, but when I noticed that every house around me had the same
problem I did, I said this is a losing proposition. I believe the
fungus would simply start again from airborne means.

It could easily become a career choice, and not one I would want.

Sheesh. From This Old House:

"The black mold-like stains and streaks that appear on roofs,
particularly light-colored asphalt shingles, is actually a blue-green
algae (Gloeocapsa magma). Commonly found in climates with warm, humid
summers, it does no damage to the roofing, but it certainly does looks
bad.

You could replace all the roofing with new shingles dark enough to
disguise the staining, or with shingles laced with copper granules,
which are lethal to algae. But that would only make sense if the
shingles were worn out.

The less expensive solution is to spray wash the roof with a 50 percent
mix of water and bleach to get rid of the algae. (No pressure washers,
please. They're likely to damage the shingles.) Just be sure to wet
your foundation plantings first, and rinse everything in clean water
when you're done. Plants don't like bleach, and wetting them with
plain water first protects them.

To keep the algae from coming back, insert 6-inch-wide strips of zinc
or copper under the row of shingling closest to the roof peak, leaving
an inch or two of the lower edge exposed to the weather. That way
whenever it rains, some of the metal molecules will wash down the roof
and kill any algae trying to regain a foothold on your shingles.

You can probably see this same principle working on roofs in your
neighborhood. Look for chimneys with copper flashing; the areas
directly below the flashing will be free of any algae stains.

The strips also work on roofs suffering from moss buildup. Just scrub
it off first with a brush, then bleach as above. "