Cleaning Roof Algae

All Around Roofing: Trusted Roofers Denver

Homeowners who live in rainy areas or areas with a lot of tree shade typically suffer from ugly black stains on their rooftops. These stains are caused by a species of algae called Gloeocapsa magma. The stains are unsightly and could damage a roof over time. A professional Denver roofing contractor can clean the roof without damaging it and install preventative measures to keep the growth from returning.

Algae requires damp and shady areas to grow, so it is more likely to affect homes in damp climates or wooded areas. It is also much more likely to occur on asphalt or wood roofs because these materials provide food. Modern asphalt shingles with fiberglass mats usually contain limestone filler to give them needed weight. The algae gorges on this filler and grows rapidly on asphalt shingle roofs. Older asphalt shingles that do not contain filler or shingles that have plant fiber mats may be more resistant.

Roof algae is often described as unsightly but harmless, but this is far from the truth. Because the algae is consuming the vital filler material in the shingle, it will weaken the shingle and cause it to fail prematurely.

It also lowers the shingles’ reflective properties, causing the asphalt to be more susceptible to UV light degradation. While roof algae is not an immediate emergency, it should not be ignored.

Treatment for algae must be done carefully to avoid damage to the roof and surrounding foliage. The most common method is to spray the roof with a diluted chlorine bleach solution. This solution can kill surrounding plants when it runs off the roof, so a safer option is to use oxygen bleach or naturally derived treatments such as roof shampoo. Pressure washing should be avoided because it can easily damage the shingles and is likely to void their warranty.

Algae problems can be stopped before they start by installing preventative measures. A common method is to attach copper, zinc or lead strips to the roof ridge. When it rains, tiny particles of the metal are carried over the roof and are naturally toxic to the algae. Another prevention method is to install shingles that have copper granules included in their topcoats. These shingles are marketed as being algae resistant. It is important to choose shingles with longer warranties or guarantees because they are more likely to have an effective amount of copper. Preventative measures are usually installed as part of a new roof replacement.

The roofers from All Around Roofing of Denver can answer any questions you have about metal roofing or siding. Ask a Question.