Roof Mold

Dennisfly · Mar 22, 2012

Many houses in my area (Virginia where it is humid) with Asphault/fiberglass shingles develop roof mold stains. My house is seven years old and hasn't developed them yet, but I think they are really ugly and would like to avoid them or remove them should they occurr.

I know they make shingles that are supposed to be resistant but I don't know if I have those or not (probably not). They also sell some kind of cleaner in Lowe's which I imagine is bleach based.

The first picture below shows a typical stain and the second shows a roof that has been cleaned and has a spotty scrubbed apearance that is not very good.

Aside from keeping the trees back does anyone know how to avoid or control this or have any experience with the cleaners?

forgeblast · Mar 22, 2012

Moss and Algae Control On Roof Surfaces

Woody65 · Mar 22, 2012

The only way to prevent it is to keep the trees away from the home and allow sunshine and air circulation to prevent moss and algae growth. The second pic with the uneven colors looks like someone took a power washer to the roof and removed the colored granules. This is usually caused by the pressure washer at too high a setting. The cleaner should be applied with a garden sprayer to kill the algae and then washed off with water. If done correctly you should not see a color variation on the roof. Good luck if you are gonna DIY or hire a pro.

KennyG · Mar 22, 2012

I can't remember the name but I got a cleaner from a roofing company and it cleaned it perfectly with very little effort. I just used a garden hose to wash it off, not a pressure washer. I've heard that bleach will also work, just not as easily.

As far as prevention, look into zinc strips.

powerpace · Mar 22, 2012

Dennisfly said:
Many houses in my area (Virginia where it is humid) with Asphault/fiberglass shingles develop roof mold stains. My house is seven years old and hasn't developed them yet, but I think they are really ugly and would like to avoid them or remove them should they occurr.

I know they make shingles that are supposed to be resistant but I don't know if I have those or not (probably not). They also sell some kind of cleaner in Lowe's which I imagine is bleach based.

The first picture below shows a typical stain and the second shows a roof that has been cleaned and has a spotty scrubbed apearance that is not very good.

Aside from keeping the trees back does anyone know how to avoid or control this or have any experience with the cleaners?

Pressure washing will get rid of the big stuff either before or after treatment with a commercial product.
A heavy copper wire on the ridge (both sides) will keep moss from forming. The exposed wire creates small amounts of Copper Sulfate that prevent fungus from growing.

Dennisfly · Mar 23, 2012

Thanks for the info guys. I think I'll do nothing until the first signs of it developing (hopefully that will be never) and then call a professional to do it. A steep pitch, not walkable without a harness, and to far above the ground for me to even think about it.

garacuda · Mar 23, 2012

Too late for this, but they make algae resistant shingles that have a small amount of zinc in the granules. I have heard that you can put zinc stips near the ridge of the roof and rainwater will spread enough zinc "runoff" over your roof to prevent algae (mold is really algae). Might want to research it some. Don't use high pressure to remove it if it shows up, it will also remove your granules, which are there to prevent UV degradation. Good Luck.

Garybake · Mar 23, 2012

They make an product just for what you describe. I personally used it on my shed that had a carpet growth on north side. It is an extreme alkaloid (oppasite scale of acid) and you just spray it on. I bought mine at Sam's Club.:thumbsup:
Welcome to Wet & Forget

buckeyefarmer · Mar 23, 2012

I got some wet and forget, trouble is I bought and forgot. :laughing: Still have it somewhere. I have AR shingles, they still have the mildew on them. Mine are 30 yr singles, on for 15 yrs and they are looking bad. Will probably replace in a couple years just due to the looks.

milkman636 · Mar 23, 2012

Last week, a metal roofing guy told me that newer shingles use limestone in the mix to meet EPA madated lower petroleum levels in their products. He said that the limestone provides the base for mold to grow both on top of and under the shigles.

He was a saleman pushing his products, but what he said does explain why an industry has recently materialized to address shingle cleaning.

After talking to him I loooked up some shingle warranties and saw 40 year and lifetime warranty shingles that had only 10 and 15 year warranties against mold growth.

Has anyone else heard this?