Preventing Algae Growth on Your Roof

preventing algae growth on your roof

If you’ve been a Hoosier for long, you know about our comically (or should we say “painfully”) humid summers. Even if the temperature is mild, the humidity alone can be enough to make you break a sweat just walking to the mailbox.

Indiana humidity can also provide the perfect environment for algae growth on asphalt shingles, resulting in dark streaks and stains. Although these stains are commonly attributed to an accumulation of dirt, mold, or mildew, the most common culprit is actually a blue-green algae known as Gloeocapsa Magma, that is spread by airborne spores.

While algae growth doesn’t harm the shingles or roofing, it is typically considered unsightly and doesn’t help the overall appearance and resale value of a home. If you already have algae stains on your roof, check out this blog we wrote last year for information on how to remove them. If you’re looking for ways to prevent them, you’re in the right place.

Trim Overhanging Branches

Trimming back overhanging branches from your roof can help “sun bleach” your roof and reduce algae growth. Algae grows best in warm, moist, dark places like a shady, humid roof. Reducing the amount of shade on your roof can help prevent algae growth.

As a side note, this method of preventing algae growth on your roof is something that you should be doing even if an algae problem isn’t your main concern. Check out this blog on how trees can affect the lifespan of your roof.

Install Metal Flashing

Another common and effective method of preventing algae growth on your roof is to install metal flashing. Metal flashing is typically used to seal areas around chimneys and roof vents, but it is also useful in reducing algae growth. This is because the copper and zinc coating on galvanized sheet metal are toxic to algae. When it rains, trace amounts of metals are washed down the roof, inhibiting algae growth.

To use metal flashing for algae growth prevention, install a strip of copper or zinc-coated sheet metal along each side of the roof, just below the ridge. Ideally, two to four inches of metal should be visible on the roof. Narrow strips of sheet metal can be attached directly to the roof using roofing nails or screws with a rubber washer. For wider pieces of sheet metal, loosen the self-sealing tabs on the top row of shingles with a putty knife. Slide part of the sheet metal under the shingles, and nail everything in place with roofing nails. (Obviously, working on the roof can be dangerous. If you feel at all unsafe installing your own flashing, please give us a call. Play it safe!)

While copper is more effective in preventing algae growth, galvanized sheet metal is less expensive. Both copper and galvanized metal are available in rolls of various widths and thicknesses. You can also purchase zinc strips specifically made to eliminate roof algae.

Install Algae-Resistant Shingles

In recent years, many roofing manufacturers (including our favorite manufacturer, Tamko) have begun making algae-resistant shingles. Algae-resistant shingles look like regular asphalt shingles, but they have copper granules embedded into the asphalt along with the normal granules. These copper granules are strategically embedded within each shingle to ensure that the entire roof is protected from algae growth.

Although this option really only makes sense if you are already considering having a new roof installed, it is definitely the easiest and most efficient way of preventing algae growth on your roof. So, when you do need your roof replaced, be sure to ask your roofer about algae-resistant shingles.

Have Questions?

Whether you just want advice on removing or preventing algae stains on your roof, or are ready to replace the roof altogether, E3 Roofing & Restoration can help. We are proud to offer a free roof inspection where we will be able to make suggestions or point out areas of concern on your roof. We can then help you decide which things you can do yourself and which areas you might need our help on.

We’re all about educating our customers and helping them make informed decisions that they are happy with. Give us a call today to schedule an appointment. We’re eager to hear from you!