- 1). Make a cleaning mixture of water and oxygen bleach. Use the amount of bleach recommended on the bottle.
- 2). Spray the cleaning mixture over the areas on your roof where the green algae is. Let the mixture sit for twenty minutes on the shingles.
- 3). Scrub the area with a long-handle scrub brush until all the algae has been removed.
- 4). Rinse off the roof with clean water from a hose to finish the job.
- 5). Buy 6-inch strips of copper and place them so that they stick out from the shingles at the highest peak of your roof. Rain that runs over the strips will pick up the copper molecules and spread them over the shingles, killing more of the green algae.
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