Algae on the Roof

What are those streaks on my roof? Why is this side of my roof black and the other side looks like a different color? The Ohio Valley unfortunately is notorious for algae… and it likes to grow on your roof.

Any slope of your roof that faces north will be a home to algae eventually. The sun burns the algae off your home on the east, south and west sides, but not the north. If you have a lot of tree coverage above your roof, algae will grow sooner rather than later. New shingles have algae protection and warranties that cover the first ten years of a new roof, but in most cases, the algae will find you after the protection period. Zinc strips are sometimes used to prevent algae when installed near the ridge of the roof. We have never installed these, because we believe the effectiveness of the zinc strips wears off during the shingles’ algae protection period.

So what can be done?

On one roof we installed a few years ago in Shelby County, the homeowner had us install copper strips near the ridge on the front, northern facing slopes of their home. This is a good solution and stopped the algae growth, but it wasn’t a cheap process.

In the end, algae growth on your roof or any other area of your home is not harmful to its performance. It’s not pretty, and can be very slick if you need to get on your roof, but your roof can be cleaned by a professional with a “special”solution. The cleaning will most likely give you a few years of algae-free shingles.

Don’t forget… Never, ever use a pressure washer on shingles!