All About Blue-Green Algae on Roofing Systems

by | Aug 7, 2020 | Roofing

Together with the siding, trim, windows and entry doors, your roof plays a crucial role in your home’s curb appeal. After all, it is one of the first things people see when they drive or pass by your property. Constant exposure to the elements, however, can affect its appearance. In time, you may begin to notice black streaks on the surface—an indication of blue-green algae growth. They may not pose any structural threat to your roof, but these microscopic yet noticeable organisms can make your beautiful roof look unsightly.

What causes them to appear? How can you prevent them from appearing? What are the ways to remove the black streaks from the roof surface? We answer these questions in today’s in-depth look at blue-green algae on roofing systems.

About Blue-Green Algae

The term “blue-green algae” is a misnomer. In reality, the organisms responsible for the black streaks on roofing systems are bacteria called Gloeocapsa Magma. It is a species of cyanobacteria that rely heavily on photosynthesis to create energy. Its greenish-blue hue closely resembles algae, which are eukaryotic organisms that are closely related to plants.

Blue-green algae thrive in humid and moist environments. It is also airborne, which means it can land and spread from one rooftop to another. It is usually noticeable on asphalt shingles roofs because the surfaces have all the ingredients it needs to survive—sunlight and moisture. The black streaks, meanwhile, come from a substance that the bacteria secrete to protect against the sun’s harmful ultraviolet (UV) rays.

According to the Asphalt Roofing Manufacturers Association (ARMA), no evidence suggests blue-green algae as being harmful to asphalt shingles. The problem, however, is that it can affect not just the appearance of your roof but also the resale value of your home. Black streaks on the roof surface detract from your home’s curb appeal, which means your property is less likely to draw the attention of buyers. Also, black-green algae can negatively impact the long-term performance of “cool” asphalt shingles roofs that reflect sunlight and heat and keep homes comfortable.

Getting Rid of Blue-Green Algae

Removing blue-green algae from your roof doesn’t necessarily mean you have to repair or replace your roof right away. You can beautify your roof anew with some thorough roof surface cleaning. Here are some cleaning solutions that are known to effectively get rid of the black stains off your roof.

  • Algae Cleaners

Many home improvement stores offer commercial cleaners that can remove blue-green algae from surfaces. Make sure you read the labels first before buying one; otherwise, the product might be too strong or too weak for the job. Also, some of the products might cause corrosion if used with pressure washers.

  • Diluted Bleach

A 1:1 ratio of chlorine bleach and water can provide the same effective cleaning action as the off-the-shelf commercial algae cleaners. A garden hose or a pressure washer is used to spray the entire roof surface with this household solution. If using the latter, be sure to use the appropriate nozzle. When spraying, the tip of the nozzle should be at least 10 inches from the surface. Leave it for 10 to 20 minutes before rinsing. As the solution takes effect, the runoff will also get rid of the algae accumulating in your gutter system.

Climbing up the edge of your roof is a fall risk, so if you choose to do the cleaning yourself, make sure you exercise the following safety precautions:

  • Use A Sturdy Ladder

The A-frame ladder might be more stable, but it doesn’t help you reach the edge of the roof. Thus, the extension ladder is more suitable for this task. If you are renting one from your nearest hardware store, be sure it has safety features like hooks that can be easily attached to the roof’s edge. As for the height of the ladder, see to it that you take the distance of your roof’s edge from the ground into account. The top part of the ladder extends at least two feet when leaned on the roof’s edge, while the base part must be set a foot away for every four feet of height for stability.

  • Get Someone to Assist You

Climbing up and cleaning your roof isn’t a one-man job. Ask a friend or sibling to help you keep the ladder steady as you get up and down and hand over things you need from the ground. They can also check the roof while you do the cleaning if ever you miss a spot.

  • Protect Yourself

Since you’ll be handling bleach or a commercial cleaning product when cleaning your roof, make sure you wear gloves, protective clothing and safety glasses to protect your skin from direct contact with the liquid. Also, wear a harness to prevent falls, whether you intend to step foot on your roof or do the cleaning from the ladder.

However, if the risks involved are too much for you to handle, you can instead turn to professionals offering roof and exterior cleaning services. See to it that they specialize in blue-green algae removal and won’t use high-pressure washing systems. These pieces of equipment can help remove stubborn dirt and stains from concrete and brick. However, if used on your asphalt roof, the shingles’ protective granules can come loose, decreasing your roof’s ability to protect against the sun’s heat and other elements.

Take your time to research your prospective roof cleaning professionals before hiring them. Apart from their licenses and insurance, ask them about their guarantees, making sure they cover blue-green algae. This is similar to a workmanship warranty in roof installation projects. Professional roof cleaning companies may guarantee streak-free roofing systems for up to a year after cleaning.

Preventing Blue-Green Algae

Preventing black streaks on your asphalt shingle roof starts with regular roof maintenance. Trim tree branches that are hanging above the roof to allow more sunshine and reduce debris. Remove organic debris like dried leaves and twigs from your roof surface using a leaf blower or other non-abrasive method. Avoid water build-up by regularly cleaning your gutter system as well. If possible, invest in a gutter protection system to protect your gutters from getting clogged.

If you are looking to install a new roof in the future, it makes sense to protect this investment against unsightly stains caused by blue-green algae. You can now find in the market algae-resistant shingles with copper- or zinc-infused granules in the market. For instance, industry-leading roofing manufacturer GAF offers asphalt shingle products equipped with the revolutionary StainGuard™ technology.

They feature thousands of copper capsules blended in with the granules that coat the outer roofing layer. They may look like any other asphalt shingle products available today, but they come with an innovative Time-Release Technology that releases up to ten times as much copper as the traditional copper-coated counterparts.

Expect long-term performance for your new roof when you install GAF shingles that bear the StainGuard Plus logo. They come with a 25-year limited warranty against algae discoloration, which means your roof is guaranteed not to have ugly black stains for a long time.

For your roof replacement needs, turn to Precision Remodeling Services. As a GAF-certified roofer, you can rely on us to install a wide range of GAF shingle products, including the ones with the aforementioned algae-fighting technology. Get started by calling (215) 360-5857 or filling out our contact form.

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