Getting stains off roof shingles

[mrtone]

First timer........ this is one fantastic forum - great info.
I'm working on moving back to SC and have found a house that has the typical (in SC anyway!) roof staining. Anyone have experience with removing this staining - I'm not sure what it is, it is dark in color.
BTW this house has plenty of room (1.4 acres) to put a new garage and I'm getting more and more anxious after looking at all the pics. I built a real nice shop in IA from Steelmaster 25'X34' - $%^& I hated to leave it behind.
Looking forward to working with you all.

1965 GTO Post Coupe

 

[Luckydevil]

Welcome, and post a pic of the roof if you can.

 

[mrtone]

http://mls-images-risco.mlsvo.com/sc-ggar/pictures/medium/Greenville1102924.jpg

That's the only shot I have of the home.

 

[bmwpower]

Same thing happens up here in NJ. Not sure how to fix it. If it were me, I would leave it be and replace the roof down the road. How old is the roof?

 

[MXtras]

Here's my take on the roof staining thing.

Obviously, it could be something that is removable - a true 'stain'. I had several tell me that the dark streaks on my old roof were from the trees that hung over the house. No one ever gave another explanation for my roof streaks and staining. What was odd was that the house across the street had the identical 'stain' yet there was not a single tree on their property. The guy across the street used some type of roof cleaner and a pressure washer and while it looked a little better, I did not think it was really worth the time and I watched as he rinsed a substantial amount of the aggregate off the shingles and into his gutters - that can't be a good thing for the shingle's survival.

Anyway, between his experience and our combined research and observations I personally believe that much of the staining is actually from the shingles themselves. I could care less what the roofing experts have said - I am always able to find an exception that their explanations can not explain or contradict.

I firmly believe that either the dies leach from the aggregates or the aggregates used to make the shingles contain iron, lead and/or other obnoxious components that oxidize and form streaks and 'stains'. I think the shingles stain themselves.

The guy's roof across the street from me has a light grey colored roof. It was several shades darker and his efforts lightened it back up a little but it was still visibly darker at the bottom than at the top. I replaced my roof with a medium brown colored roof that seems to be less suceptable to the staining and it's holding up well.

So - basically I think that the stains are un-avoidable in many shingles unless you can keep them from getting wet and protect them from the environment - not too likely nor very convenient. I never dug into it far enough to recognize a trend among the manufacturers and/or the colors. Right or wrong, that's my story and I am sticking to it.

Scott

 

[bmwpower]

Here's my take on the roof staining thing.

Obviously, it could be something that is removable - a true 'stain'. I had several tell me that the dark streaks on my old roof were from the trees that hung over the house. No one ever gave another explanation for my roof streaks and staining. What was odd was that the house across the street had the identical 'stain' yet there was not a single tree on their property. The guy across the street used some type of roof cleaner and a pressure washer and while it looked a little better, I did not think it was really worth the time and I watched as he rinsed a substantial amount of the aggregate off the shingles and into his gutters - that can't be a good thing for the shingle's survival.

Anyway, between his experience and our combined research and observations I personally believe that much of the staining is actually from the shingles themselves. I could care less what the roofing experts have said - I am always able to find an exception that their explanations can not explain or contradict.

I firmly believe that either the dies leach from the aggregates or the aggregates used to make the shingles contain iron, lead and/or other obnoxious components that oxidize and form streaks and 'stains'. I think the shingles stain themselves.

The guy's roof across the street from me has a light grey colored roof. It was several shades darker and his efforts lightened it back up a little but it was still visibly darker at the bottom than at the top. I replaced my roof with a medium brown colored roof that seems to be less suceptable to the staining and it's holding up well.

So - basically I think that the stains are un-avoidable in many shingles unless you can keep them from getting wet and protect them from the environment - not too likely nor very convenient. I never dug into it far enough to recognize a trend among the manufacturers and/or the colors. Right or wrong, that's my story and I am sticking to it.

Scott

Sounds like a likely explanation to me. I have seen some houses with no trees anywhere nearby...same stains.

 

[mrtone]

The house was built in '96 so 10 years old.
The more I read up on it I'm learning that its an airborne type fungus. Several companies specialize in cleaning this stuff off. I've read that the fungus feeds on the shingles and unless you buy high-end shingles that have special inhibitors, you can get the fungus.
I too dont think shrubbing or pressure washing is a very bright idea. But there must be a chemical that can be simple sprayed on to kill this stuff.
I've read that zinc strips placed on the top rows will wash down onto the roof and inhibit the fungus from growing.
Who knows...................

 

[mike s]

My roof has the same problem. It is 6 years old. My stains are only on the north side. It doesn't get direct sunlight, ever. No trees close by. I don't think it is from the shingle because the rest of my roof is fine. I think it is some kind of fungis or mold. Let us know what you find out. Would like to get them off. Mabey bleach in a sprayer would work. Think I'll try it.
Mike

 

[mrtone]

I wouldn't do the bleach thing - I've read that it weakens the shingles.
This outfit has some interesting info on the problem - and of course, their solution. There are many others on the net.
http://www.saferoofcleaning.com/

I'd still like to find out what works best for the cheap guys like me.

 

[Bill K]

It's an algea growth. If you look closely the stains start as a small spot and get wider down the roof. There are several companys that specilize in remoing them around here. I donlt know of any first hand experience with them.
Bill

 

[Krodad]

I concur on the algae growth.

why it occurs? In the photo you can see that it is a regular pattern, mostly following the rafters...these are also areas of thermal bridging, though minor, but enough to cause regular condensate formation, and propagate the algae growth in those areas. All it takes is a little longer period of moisture, on a regular interval, and the algae decides that this is a great place to be. In Virginia, you have cool, humid nights. As the attic cools down overnight, so do the rafters. As morning sun rises, the surface temp. of the roof heats up faster than the attic area, and now a cold spot (lines) occur on the roof surface at the rafters...the morning is still very humid and the dewpoint occurs on these cold areas, now you have condensate...minor and maybe not visible from the ground, but it's there. Similar conditions are what can cause ghosting on interior drywall if the insulation and vapor retarders are not installed correctly.

As stated in an above post, zinc strips will fix the problem, at least they will prevent further staining. I have a big barn with a couple galvanized cupolas...the roof shingles are stained, except for broad areas that follow the watershed beneath the cupolas...perfectly clean shingles, and they are in MUCH better condition than the rest of the roof. Almost like they are less than half the age of the other parts of the roof. The zinc is sacrificial, and as it leeches down the watershed, it creates a self-cleaning effect as well as inhibits mold and fungi growth.

 

[red caddy]

Down here in the swamp, we clean the roof twice a year(spring and fall) with pool chlorine and a garden sprayer. I usually just let the next rain wash it off. no stain survives a hot oxidizer wash. RED