1. The Goal: Clean asphalt shingles safely & cheaply to improve appearance, primarily by killing black algae streaks and moss.
2. The Method: Soft Washing
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Never use a high-pressure washer. It strips granules and destroys shingles.
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Use a low-pressure garden sprayer or hose.
3. The Chemical: Oxygen Bleach
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The active ingredient is Sodium Percarbonate.
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It’s a safe, non-chlorine powder that kills organic growth without harming plants or shingles.
4. The Cheapest Source:
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Buy pure Sodium Percarbonate in bulk online or at a pool supply store. It’s cheaper and more effective than branded laundry boosters like OxiClean.
5. The Recipe:
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Mix 1 lb of Sodium Percarbonate per gallon of HOT water in a 5-gallon bucket.
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Add 1 oz of laundry detergent (optional, helps it stick to the roof).
6. The Process:
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Safety First: Use a sturdy ladder and a safety harness.
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Wet Plants: Soak vegetation below the roof line with plain water.
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Apply: Spray the solution evenly onto the dry roof. Start from the bottom.
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Dwell: Let it sit for 15-20 minutes. Do not let it dry.
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Rinse: Gently rinse with a garden hose on a “shower” setting.
Bottom Line: For pennies per square foot, this method cleans effectively and extends your roof’s life without causing damage.