Dottie wrote:

I live in FL where algae growing on the roof is a big problem. When I
had a tile roof I had it sprayed every year with some kind of
mildewcide....a man comes around and does several houses in the
neighborhood. Last June I got a new GAF ultra Timberline shingle roof
that is supposed to be pre-treated with some kind of chemical to keep
algae from growing. So, when the man came around I said I wouldn't be
needing the treatment anymore. He said the stuff that was used to pre-
treat roofs didn't really help and I should go ahead and let him treat
mine. I didn't .. because I was afraid it might affect the warranty.
I called the contractor who said I didn't need anything else and I e-
mailed GAF while waiting to hear from contractor. Haven't heard back
from them.

Thing is, there are several houses around me who have newish roofs -
older than mine but not a lot older - and they are beginning to show
dark spots in places. Now I am wondering if I should call the guy
back and have him treat my roof before I get spots ... Anybody know
whether the GAF anti-fungal properties really work or not? Thanks.


Do the neighbors have lighter color roofs? More shade? I once read
that light color roofing,
while helping reflect heat and keep it out of the attic, grows more
mildew because it doesn't
get as hot as a darker color. Can't prove it by me. Only place on our
condo exterior walls that mildew
used to thrive was on shaded areas - behind downspouts, behind some
vegetation. Since
repainting, there doesn't seem to be any.

Be clear about what your roofing is supposed to be "anti" - mildew and
algae can be pretty different..

This link is pretty interesting:
http://www.inspect-ny.com/roof/shinglestains.htm