In late 2018 I noticed discoloration on my 4-year old shingle roof in Florida. The area affected was in the shade of trees most of the day. I did some research online and discovered that black algae and moss tend to grow on shaded and damp areas of the roof. There were a number of cleaning kits recommended, but I was looking for a more permanent solution. I came across some articles that described the use of copper or zinc strips near the top of the roof line. The theory was that rain water would wash the copper or zinc salts down the roof and this would protect the roof from discoloration due to algae or moss formation. In addition to the theory behind the solution, there were some case histories to back it up. However, reader comments (presumably from those who tried the solution) were somewhat mixed. Some had success with it and some did not. The mixed results may have been due to different locations and environments. I decided to give it a try and purchased some sheets of copper plate which I tucked and attached under the top line of shingles. (see picture below)
I took some pictures of the problem on the day I attached the copper strips and then again three months later. You can see the results below.
Here is a picture taken just after I installed the copper strip at the end of November 2018 You can notice the ugly discoloration on the shingles.
The picture below is of the same area taken in mid February 2019. I was hoping that the strips would prevent further discoloration but was pleasantly surprised to notice a marked improvement in the area. It does appear that the metal salt wash after rainfall, not only inhibits but kills standing agae/moss growth.
I shall take more pictures of the roof in a years time and update this post to confirm the long term efficacy of the solution – at least in my area of sunny and rainy Florida.
Educhirp 