How to Clean Algae Off a Shingle Roof

If you have ever noticed that your roof shingles are streaked with uneven black or green marks, you are likely seeing roof algae. Roof algae lives off of the materials that shingles are made from--mainly limestone or calcium carbonate. The microorganisms do not cause the shingles harm, but many homeowners choose to clean their roof to make their home more aesthetically pleasing.

Things You'll Need

• Oxygen bleach
• Bucket
• Ladder
• Pump sprayer
• Push broom
• Garden hose

Instructions

1. Buy a bucket of oxygen bleach from your local home improvement store. Oxygen bleach will not discolor your shingles and is not toxic. Read the directions on the bucket to know how much water to add to the powdered bleach for a workable solution, as strengths may vary.

2. Fill a pump sprayer, also available at hardware stores, with the water and bleach solution.

3. Use a ladder to climb up to your roof. Wear rubber-soled shoes that give you adequate traction when you are working on a slippery surface.

4. Spray the oxygen bleach on the roof, being sure to saturate all of the roof algae. Allow the bleach to soak into the shingles for at least 15 minutes.

5. Scrub the shingles with a long-handled push broom. The oxygen component of the bleach will be foamy and will already have begun to kill the algae.

6. Rinse the roof with clear water from a garden hose. In some cases, you may need to apply a second spraying of oxygen bleach to clean all of the roof algae away.

Tips & Warnings

• Oxygen bleach evaporates very quickly in the hot sun. Try to work on your roof at either end of the day when the weather is cooler.