This is a post about roof algae, before and after treatment.
Over two years ago I wrote a blog post about the black algae that plagues so many shingled roofs. Technically this algae is called Gloeocapsa magma. In the post I published a formula to spray on it to hopefully eradicate the algae.
This is an aggressive algae, which if allowed to grow unchecked can become really difficult to get rid of. The two lower photos of the following post are of my roof: Black algae
This algae growth has become a huge problem in our area. I did not get dinged by the HOA until this fall when, apparently, virtually everyone in my neighborhood did! Who knows about everyone else, but I was given until October 31 to correct my roof.
In the past two years I had experimented with formulas to get rid of it. The formula that I published in that post worked only MINIMALLY! Purchasing three other solutions on line, all GUARANTEED to eliminate the algae was unsuccessful too.
Since my post two years ago the problem had gotten MUCH WORSE.
So this fall I experimented with my original formula. Here is the result. The HOA's photos before treatment, and my photo October 21. There are only two here.
Yesterday's photo was an attempt to mimic the association photo for comparison. The areas around and under the dormer were the worst on the roof. I had previously sprayed my new formula on the lower half of that section of roof to see if it worked. And it did. These areas around the dormer were very bad, and very solidly black. This was so, I think, because that is the section of roof with the most slant, and therefore it is the most oblique to the sun. It took TWO applications of formula.
Again, my photo mimics theirs. It came out excellently! This, and the middle section of the roof, only took one application. There was a lot of staining, but it wasn't as caked and fully developed as the areas near the dormer.
So, what's the formula?
In a 5 gallon bucket mix:
1 Cup TSP Substitute (use the substitute powder because it is more environmentally friendly. The TSP helps the chlorine to stick to and kill the algae. I mixed it well in a quart of hot water to melt it before adding it to the solution. I bought it at Lowe's in a quart carton for $11)
1 Gallon of Water
3.5 Gallons of Clorox
Spray to cover completely over the entire roof surface, but hit the dark areas very, very well.
Rinse very well!
Near the dormer I let the first application sit for five hours before rinsing it. It worked about 95%. We hit it again when we did the other two sections of roof. This second application over the whole roof stayed overnight before rinsing in the morning.
I also sprayed my grass with lots of water before and after the rinsing. And when the rinse water splashed from the downspout it was very dark with muck.
I did my whole roof for about $35. There is a company in the area doing the same thing but for my roof they charge many hundreds of dollars. AND, they do not give a guarantee as to how long the job will last!
My recommendation: even if you hire a handy man to climb up and spray the roof, this formula is very cheap. And if it worked on my roof, on which the algae was very developed, it should work on yours! Good luck! Again, in severe cases two applications may be necessary. But rinse well!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560