Algae and Moss Growth on Your Roof

Have you ever seen a roof that had dark streaks running down or across it? This discoloration is usually caused by algae or moss growth. It is important that you take steps to prevent this in order to get the most out of your roof.

algae on the roof

Algae vs Moss

First, let’s start with the difference between algae and moss growth on your roof. The majority of the time, those dark streaks running down your roof consist of algae. Humid climates are the most susceptible to algae growth on roofs.

Algae growth occurs in areas where water tends to collect on roofs. The most common type of algae, blue-green algae (gloeocapsa magma), uses a dark pigment to protect itself from ultraviolet rays.

By the time you see streaking from algae on your roof, it has most likely been there for several months and intervention is necessary to protect your roof.

It Spreads Quickly

If you see algae growth on a neighbor’s roof, you can expect to see it appear on your roof too. Algae spores spread by being carried by the wind or by animals from one house to the next. Although there is no evidence to suggest that algae growth will affect the structural integrity of your roof, it will affect the look, and could negatively impact the value of your property.

Moss is a little different, however, it travels the same way as algae. Moss tends to grow on the parts of roofs that don’t see much sun and therefore stay damp longer allowing moss to grow. Moss has a root system and obtains water through its leaves.

Because of these attributes, moss growth can be detrimental to your roof. It can cause shingles to curl and become separated from the roof. If the moss buildup is substantial enough, it can cause water to collect and severely damage your roof.

Steps to Take

Don’t fear! If you spot moss and algae growth on your roof, there are some steps you can take at home to take care of the problem. Start by mixing a 50/50 solution of chlorine bleach and water in a sprayer.

The bleach you use for your laundry will work just fine. Spray this solution on the affected area and let it sit for at least 15 minutes, longer for more stubborn areas. After the solution has done its job, rinse the area with low-pressure water.

Be smart and use protective gear when using bleach, and make sure you take precautions with the surrounding landscaping. Give it some time, while algae may disappear with one treatment and a few good rainstorms, moss may take multiple treatments and a little more elbow grease to get rid of it.

There are some proactive steps you can take to prevent moss and algae growth on your roof:

There are materials available when building your roof that are designed to discourage, or even completely prevent the growth of algae and moss. Consult with your local roofing supply store to see all options available.