ANDERSON TWP. I couldn't take it any more. The dark stains on my roof were driving me crazy. I resolved to find out what was causing them, and more importantly, how to make them go away.
The stains look like mildew. I had lived in Florida some years ago and remember that the warm, humid climate allows molds and mildews to grow on virtually any surface, including roofs.
Some fellow Tri-State residents told me the stains on our rooftops here are caused by climate change. I decided to investigate applying my 20 years of reporting acumen.
What I discovered in my research is that the stains are alive! They're a living organism. Specifically, we're talking about an algae called
gloeocapsa magma.
The reason we didn't see it years ago is roofing shingles were made of different materials back then. They're still made with asphalt, but the base is now fiberglass instead of organic cottons or felt.
The trouble began when manufacturers started using limestone to add heft to the light fiberglass. It turns out the algae love to feast on limestone. Just add water and shade – and soon enough you'll see the stains appear on your roof.
Some newer shingles include small grains of copper or zinc to ward off algae growth. Copper is poisonous to gloeocapsa magma, even in the small amounts that leach out with every rain shower.
Several web sites promote and sell zinc strips you can install near your roof peaks to prevent future algae development, but some professional roof cleaners say those strips lose their effectiveness over time.
Professional roof cleaning is an option I explored. Local companies charge in the neighborhood of $400 to remove algae stains. They offer guarantees, and you don't have to risk injury or death by climbing onto the steep pitch of your roof to do the job yourself.
In this economy, I decided to try my own remedies first, before seeking professional help (pun intended).
Again, don't try this at home unless you're reasonably confident you can safely get up on your roof without the risk of slipping off. Do so at your own risk. Most importantly, never step on an area where there's moss growing, or where you've just cleaned because it will be very slippery.
Fortunately, my stains were confined to an area above my front porch. I could put up a ladder there, get onto the roof itself, and the farthest I could fall would be about eight-feet onto the faux balcony. Clearly, I was desperate to get rid of these stains!
Some online retailers charge as much as $150 for a couple gallons of roof stain cleanser. What liquid on Earth is worth that much (other than oil about a year ago)?
Several helpful web sites – like
askthebuilder.com – suggested using deck cleaner. The key is most deck cleaners employ oxygenated bleach. It's not chlorine bleach, so it's supposedly safer for plants, pets and your roof.
I found a name-brand deck cleaner selling at $20 for two-and-a-half gallons. I used a regular old $15 garden sprayer to apply the deck cleaner directly on the algae stains.
While I was up on the roof, I noticed there was also moss growing under the edges of the shingles themselves. The oxygenated bleach turned the green moss white almost instantly.
I gave the deck cleaner about a half-hour to do its work, then I returned with a garden hose. A thorough spraying with the nozzle cleared all the bleach off the deck and sent it draining into my gutters.
After the roof dried, I noticed quite a difference. Some of the stains were still visible, but this basic treatment removed about 80% of the problem.
A few days later, I tried again. This time I used a soft scrub brush just to remove the moss. Because it had been killed by the earlier treatment, the moss came off very easily.
I decided to leave the deck cleaner on for about an hour after the second treatment.
One note about rinsing with the hose: don't use too high a pressure with the water, and never spray up under the shingles. Let the water go up in the air in an arc before coming back down onto the shingles where it can drain down toward the gutters. This will help prevent roof damage.
The second treatment worked wonders. It looks like a new roof!
All it cost me was about $35 in materials, a little bravery (or stupidity) to climb the roof – and two cans of wasp spray!
