roof shingles

How To Remove Algae From Your Roofing


On the parts of your roof that don’t get much sunlight, algae can begin to form on the shingles. Often mistaken for mold, algae on shingles appears as black streaks. Algae on your roof shingles doesn’t just discolor them—it can also damage them over time. If left to progress, algae can eat away at the materials in your shingles, causing deterioration of your roof. Luckily, cleaning algae from your shingles is a fairly simple process. There are a couple of options to consider if you want to rid your roof of algae marks.

Use a Bleach Mixture

The most common method for cleaning algae from roofing is to use a mixture of bleach and water. Mix 1 part bleach with 3 parts water in a two-gallon bucket and add one teaspoon of trisodium phosphate (TSP).

This mixture can be applied to affected shingles using a handheld pump sprayer, and should not be applied to shingles that are not showing algae growth. Let the mixture sit for around five minutes, and then thoroughly wash all residue away with water.

If any algae remains, you can repeat the process, but only after allowing the roof to dry completely. Avoid using a pressure washer to rinse away residue, as the concentrated spray of water can damage shingles and make algae problems worse.

Caution: make sure to wear gloves and a mask to protect your skin and lungs from the chemicals. If there are any plants in danger of coming into contact with the bleach mixture, rinse them down with water before and after applying the mixture.

Use Oxygen Bleach to Reduce Risk of Damage

If you are concerned about household bleach damaging your plants or shingles, powdered oxygen bleach is a safer alternative. Similar to the previous process, you can mix oxygen bleach with water and spray it on the affected shingles.

Once you let the solution sit for 10-15 minutes, you may need to use a scrub brush to remove all of the algae. It is important that you scrub only using a downward motion to avoid damaging the shingles.

Preventing Regrowth

The most common way to prevent algae growth from returning once it has been removed is to install zinc or copper strips along the roof’s edge. These work by killing algae blooms when the metal ions are washed down the roof with rainwater. Copper ions can also stop asphalt shingles from oxidizing and drying out, making them last longer.

If you think that algae growth has damaged your shingles and are unsure if your roof needs to be repaired or replaced, contact Asonic for a free quote! We provide quality roof repair that doesn’t break your wallet. A complete list of our roofing services can be found here.