DIYbanter - View Single Post - Removing black algae stains from roof shingles

Ray K

Ken wrote:
wrote:
On Jun 24, 9:37 am, Ray K wrote:
When a roof has copper or galvanized items (vent pipes, exhaust fans,
etc.) protruding from it, shingles below these items will be free of
algae stains because rain washes copper or zinc from the galvanized
items off and kills the algae. Has anyone heard of using a copper or
zinc solution in a hose end sprayer to clean remove the stains? If so,
which chemical, what concentration, and what coverage?

I'm experimenting with more conventional approaches (oxygen bleach,
laundry detergent, and a produce called KrudKutter). All require
multiple applications, "scrubbing" with a broom, and generous rinsing.
There may be other proprietary (expensive) items that are more
effective
and easier to use, but for now I'm looking for shortcuts.

Thanks,

Ray

Roof zinc strip?
Just install, let the rain do the work. Don't know how fast the stains
will fade, though.

Dave

You are correct about the zinc being responsible for SOME killing
of the algae/fungus. I guess depending upon where you live, the
results of such strips will vary? All I can say is that in the south
where the humidity is high and the temperature is also, the strips do
not work very well. There IS an improvement, but I do not see it as
worth the effort.

Some years ago I attempted to remove the stains from my roof with
a chemical made especially for this purpose. You can buy it at Home
Depot I believe. It is mixed with bleach, sprayed on with a tank
sprayer, and washed off with a hose or pressure washer at low
pressure. The results were NOT total, but there WAS an improvement.
The real problem was that the improvement was only temporary and if
your neighbors had the same problem, it was sure to return next year,
albeit not as bad.

If someone wants to make a fortune, they should find something
that solves this problem and mix it into the asphalt used to make the
shingle. As of this moment I do not think there is anything that
really prevents the problem 100%. If there is, I would like to hear
about it.

The problem is caused by the limestone used in the construction of
current shingles. It acts as food for algae. There are shingles made
with embedded copper granules in them that prevent the algae problem.
You just have know they exist and specify them.

The problem with adding zinc strips is that they will take too long to
work. That's why I was wondering if there is a zinc (or copper) solution
I could just spray on the roof to remove the stains fast.