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Prevent Algae Growth on Your Roof

Algae may not be harmful to your roof, but the dark streaks and discoloration they produce can look awfully unpleasant. Besides being an aesthetic problem, roof algae can also pose a major financial setback.

Algae spores are normally spread across rooftops by animals and wind. The algae thrive where moisture tends to dwell on the roof surface. As Pittsburgh’s premier roofing contractor we believe one the most common types to grow on roof surfaces is blue-green algae. Algae could have been growing on your roof for months by the time you start seeing the dark streaks. Sometime mold is present as well.

In this article, we share with you some valuable tips on how to prevent algae growth on your roof in the first place.

Let’s get to it.

  1. Trim Over-Hanging Tree Branches

Are there tree branches hanging over your roof? Maybe there are trees that cast shade on a part of your roof for prolonged periods of the day?

If so, you need to trim them back. You want your roof to have direct sun exposure. This will help prevent excess accumulation of moisture. It will also help reduce the amount of debris that falls onto the roof from trees.

  1. Get Rid of Debris Regularly

If you usually have debris accumulating on your roof, it’s important to remove it on a regular basis. A leaf blower comes in handy during this process. When using a leaf blower, blow the air down the roof. This will push the debris away. You don’t want to push the debris into the crevices and around shingles by blowing it upward.

Keep in mind that a power sprayer is not recommended for clearing debris, especially in the case of asphalt shingle roofing, because it could damage the roof and shorten its lifespan.

  1. Install Proper Ventilation

Ventilation plays an integral role in preventing moisture problems that result in algae growth. You should install an efficient ventilation system beneath the roof deck. This will help minimize the accumulation of heat and condensation in the attic area.

A proper ventilation system upholds a continuous and balanced flow of air, which eliminates humidity and brings in cool, dry air. The dry air protects your roof and house from moisture damage.

  1. Maintain Clean Gutters

Be sure that your gutters are always clear of debris. You want water to drain efficiently from the roof. It is imperative that the gutters and downspouts be positioned in a way that allows water to flow down to the ground and away from your home’s foundation. The water should not flow onto the lower parts of your roof.

  1. Introduce Copper of Zinc

These complex-celled organisms abhor metal. To help prevent algae from growing, consider cutting about 5-inch-wide strips of copper or zinc and placing these strips under the ridge of your roof.

When it rains, copper carbonate will be washed down. This compound is effective in preventing algae from growing. But there’s a catch: it is not advisable to add copper or zinc strips to an existing roof because, to do so, you will have to either apply the strips with exposed nails or break the sealant bond to slide the metal strips under the shingles. Using nails may lead to leaks over time while the latter approach may eventually lead to wind damage.

The use of copper or zinc to prevent algae growth works best when replacing your roof or constructing a new home. In fact, you can install asphalt shingles that incorporate copper granules. There are several types of shingles that integrate algae-resistant technology. Do your research to find the best one that suits your needs.


Algae growth on roofs is an unsightly nuisance. Fortunately, there are several ways to prevent algae growth on your roof. You can keep tree branches trimmed back from your roof, get rid of debris, install proper ventilation, and keep your gutters clear of debris. Be sure that these activities are part of your regular roof maintenance plan.

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