I had ugly black stains on my roof shingles. I read up on it and first
used oxalic acid. That didn't work and I tried household bleach. The
black stains disappeared but left an ugly light brown stain in its
place. I tried bleach twice more. The last time I used nearly full
strength bleach. Before the bleach could dry (I did this in the early
morning before the sun hit the roof), I washed the bleach off with a
hose. The brown is still there; looks worse than the black mold because
the light brown really stands out against the dark shingles. It makes
the whole house look shabby.

Now I'm getting really frustrated. I didn't want to use a power washer
but I feel that I'm left with no choices. I use a 40 degree tip (the
widest tip) on the power washer angling down on the shingles (never
pointing up the roof).
The power washer is extremely powerful so I don't want to get too close
and damage the shingles. The power washer does reduce the brown stains
somewhat. In the higher elevations of the roof where I didn't want to
spray up and get water under the shingles, the brown looks positively awful.

I believe that my original mistake was not rinsing the bleach off on the
first pass and I caused the brown stain to become permanent.

Does anyone have any suggestions on how to proceed from here?

Bob wrote in message ...
I had ugly black stains on my roof shingles. I read up on it and first
used oxalic acid. That didn't work and I tried household bleach. The
black stains disappeared but left an ugly light brown stain in its
place. I tried bleach twice more. The last time I used nearly full
strength bleach. Before the bleach could dry (I did this in the early
morning before the sun hit the roof), I washed the bleach off with a
hose. The brown is still there; looks worse than the black mold because
the light brown really stands out against the dark shingles. It makes
the whole house look shabby.

Now I'm getting really frustrated. I didn't want to use a power washer
but I feel that I'm left with no choices. I use a 40 degree tip (the
widest tip) on the power washer angling down on the shingles (never
pointing up the roof).
The power washer is extremely powerful so I don't want to get too close
and damage the shingles. The power washer does reduce the brown stains
somewhat. In the higher elevations of the roof where I didn't want to
spray up and get water under the shingles, the brown looks positively
awful.

I believe that my original mistake was not rinsing the bleach off on the
first pass and I caused the brown stain to become permanent.

Does anyone have any suggestions on how to proceed from here?

quoting my post from last month in thread about power washers:

I live in Houston, a swamp of algae and mildew, so my 'new' house has
some algae on the bricks. I wanted to try chemical removal first before
pressure washing. I'm not certain if bleach will have any effect on algae
(as it does on mildew). I browsed at Lowe's and found several spray-on
cleaners for houses. Then I found this stuff at Ace Hardwa
www.sprayandforget.com specifically for algae. It was expensive per gallon
but it seems to work well at killing the stuff, plus it leaves a residue
that keeps the stuff from growing back. It doesn't have the immediate effect
that power washing would but then power washing can damage siding, etc.
(update: this is cool stuff, it's working well).

Check out their website, they show some machine to spray roofs. Don't know
about the bleaching effect from the bleach, could be permanent.

You should have used M1 roof and deck
cleaner from Home Depot with a small
pressure washer with 40 degree tip.
You have nothing to lose try it now.

Are you sure the brown isnt the tar comming up, you need to show it to
someone that knows before you make it possibly worse.

m Ransley wrote:
Are you sure the brown isnt the tar comming up, you need to show it to
someone that knows before you make it possibly worse.


No, it's not the tar. I got a little bit more aggressive with the power
washer and I was able to further reduce the brown stain.

I'm going to try some of the products that other posters have suggested.