On Wed, 16 Jan 2013 08:15:35 -0600, "HeyBub"
wrote:

wrote:

I got black algae on my garage shingles. The cure is oxyclean spray.
Black does not mean it has to be mold.

Good point. Algae is more likely. Not all black mold is created
equal, either. Not all black mold is black, either. ;-)

And, in the Houston area, it could just as easily be dirt. Or at least the
particulate matter from engine exhausts.

If it were dirt here, it would be red, not black.

What you COULD do to help is power-wash the affected concrete, then apply
multiple coats of concrete sealer.

That's like work[*]. Not sure it's a good idea either.
[*] selling the house.