My roof has skid marks. And lichens. Next thing you know, it could grow a mossy beard. What’s going on here? And more important, what can I do about it?
You might be wondering the same thing,… if your roof is looking a little black or green around the edges. Or you might be blissfully unaware that little organisms are taking up residence on your rooftop.
It’s worth taking a look, at least from ground level. You might also be able to get a look from an upstairs window. Use binoculars if you need a close look. And if you think you have any of them and you’re not comfortable on ladders, call a pro to take a look.
The first of the three little plagues on asphalt shingles is easily seen from the street. You’ve probably seen it on hundreds of homes. It looks like someone dumped ink on the roof and it ran down toward the gutters. Some houses show only a few streaks, and others look like most of the roof has been painted.
For years, I figured shingle makers had changed something in the manufacturing process that didn’t hold up as well as it should.
But the Asphalt Roofing Manufacturers Association want us to know that it’s not their doing. Those skid marks are the work of algae with a massive name that sounds like something involving a volcano: Gloeocapsa Magma. And it travels with the wind.
It “tends to collect and grow upon roofing structures. Natural pigments produced by this algae may cause a white or light-colored roof to gradually turn dark brown or black,” says the association based in Washington, D.C.
The algae is widespread in the Gulf States and along the Northwest and Eastern seaboards, but a quick look at Ohio rooftops shows it isn’t confined to those places.
The association notes that algae-resistant roofing is now available, so if you’re in the market for a new roof, you might look for that.
If you’re facing skid marks on your roof, the association says that removing stains isn’t easy, but it recommends applying a solution of chlorine bleach, trisodium phosphate and water. Solutions range from one cup TSP and one gallon of bleach per five gallons of water to one cup TSP and 2.5 gallons each of bleach and water.
Most of us, including someone like me who isn’t afraid of a ladder, should probably hire someone to do this work. There are several companies in central Ohio that specialize in roof cleaning. And some of them use solutions that might be gentler than the chlorine-based recipe suggested by the association,
The association says that if you tackle it, gently disperses the solution on the roof, using normal precautions for handling bleach, and applies carefully to avoid damaging other parts of the house and landscaping. Then rinse it off with low-pressure application of water.
Avoid scrubbing, because that will remove the sand-like aggregate from the shingle and reduce its life or even damage it. Whatever you do, don’t power wash an asphalt roof. You’ll blast that aggregate off of the shingles and drive water into places it shouldn’t be.
Oh, and here’s the best part: “The effectiveness of such cleaning techniques are only temporary, and discoloration likely will recur.”
You might think, “In that case, why bother?”
Consumer Reports provides a reason: “When left unchecked, it can damage shingles.”
Dangit. I hate when that happens.
The Consumer Reports author contacted several companies and received quotes of between a few hundred dollars and $1,500. In the end, he contracted with a “roof shampooing” company that charged $350.
Now, if you have lichens or moss, they’re likely growing in a shady place. So, if you can reduce the shade by trimming trees, for example, that will help.
Either way, you should probably take action, or hire someone to attack them. Unlike algae, lichens and moss hold moisture and are likely to put down little roots. They can work their way into the shingles and do damage with the help of Mother Nature: rain + little holes caused by little roots + freezing and thawing = damage.
Some experts recommend using the same type of cleaning solution suggested by the association to fight algae. Several recommend installing zinc or copper strips of metal near the roof ridge. Elements in the metal slowly dissolve in rainwater and flow down over the roof to prevent lichen or moss growth.
After watching a video on the process at This Old House, I’m inspired to tackle those skid marks.
View original article at: Old House Handyman: Cleaning can rid roof of algae, lichens