5 Frequently Asked Questions About Cleaning Off Roof Algae

After looking at your roof, you might notice dark, streaky areas that appear to be tar or dirt. However, these are probably not dirt, and are most likely caused by a form of algae called Gloeocapsa magma that tends to grow on asphalt roofs. Below are answers to five frequently asked questions about this form of cyanobacteria.

Will The Algae Hurt The Roof Or Is It Only A Cosmetic Problem?

While at first you may only need to be concerned about your roof's appearance, this form of algae is more than a cosmetic problem. The longer it remains on your shingles, the more it will eat away at the material. 

If allowed to stay on your roof, the algae will eventually cause rotting and rapid deterioration. This will then cause your roof to leak, requiring you to have parts or all of it replaced.

What Is The Best Way To Clean Algae Off The Roof?

In order to clean the algae off of your roof, any existing growth will need to be removed. The shingles will also need to be thoroughly cleaned and treated to kill any spores that have embedded themselves within the cracks and crevices of the asphalt.

There are commercial cleaners available that will not only kill the algae, but also coat your roof with a residue that will prevent it from coming back. If you plan to clean the roof yourself, a solution of one part bleach to three parts water is an effective, homemade cleaning solution.

Will Pressure Washing The Roof Get Rid Of The Algae?

While pressure washing will remove the surface growth, it will not remove all of the spores. In fact, it could make the problem worse. The water will give the algae spores the extra moisture they need to thrive. 

Pressure washing your roof is also not recommended because it could cause the shingles to become dislodged. If you decide to clean the roof yourself and need to rinse it, use a garden hose with a spray nozzle and use it on the medium setting.

Can The Cleaning Process Take Place At Any Time Of The Year?

Ideally, you should hold off on cleaning your roof until the forecast calls for a warm, sunny day when the temperature is above 50 degrees Fahrenheit. The sun and warmth will help activate the chemical cleaner, making it more effective. The sun's rays will also help cook the chemical-drenched algae, increasing the chances that more will be killed with the first application.

However, you do not want it to be extremely hot or the cleaner may evaporate before it has time to thoroughly kill the spores. You may want to choose a day in the spring or fall when temperatures are more temperate. 

Does The Entire Roof Need Cleaning Or Only The Affected Areas?

Although it may appear as though only part of your roof is affected, those are the areas where you are able to actually see the growth. If one part of your roof has algae, there is a good chance that spores have landed and started to grow on the entire roof.

Because they is a high probability that you have more growth than you can see, the entire roof should be cleaned and treated. This will also prevent any spores laying dormant from sprouting and recontaminating the rest of the roof.

If you suspect that you do have algae growing on your roof, you have the option of trying to clean it yourself. However, if you are not comfortable doing so, you may want to contact a roofing company to learn more or to schedule an appointment. They can send someone out to clean it for you, as well as assess any damage that may have been caused by the algae.