Can Moldy Roof Shingles Be Cleaned, or Must It Be Replaced?

Surface mold on asphalt or fiberglass shingles can often be washed away with a soft brush and a mild cleaning solution. You can try this if the mold is only on the surface and the shingles are still intact. Avoid pressure washing, which can force water under the shingles and cause leaks.

For wood shingles, cleaning is trickier because mold can soak into the grain. If the shingles are solid and the mold is light, a gentle scrub may work. Always let the roof dry fully afterward, and check for any soft or crumbly spots that signal deeper trouble.

• Use a soft-bristle brush, not a power washer
• Work on a dry, mild day
• Rinse with low-pressure water
• Let the roof dry completely before judging
• Look for cracks, curling, or missing granules

For a do-it-yourself attempt, mix a mild detergent with water and apply it with a soft brush. Work in small sections, rinsing with a garden hose at low pressure. Never use bleach on asphalt shingles, as it can accelerate aging.

Protect yourself with gloves, long sleeves, and eye protection. If the roof is steep or wet, let a pro handle it. Falls are a real risk, and a pro has the right safety gear and experience to work on sloped surfaces.

If you see mold covering a large area, or if the shingles feel soft or brittle, it is time for a professional assessment. A local water damage pro can tell you whether cleaning will work or if replacement is necessary. They can also spot hidden leaks that you might miss.

A pro can also clean safely without damaging the roof. They know the right techniques and equipment. If the mold is extensive, they may recommend replacing the affected section. Either way, getting a professional opinion early can save you from a bigger water damage problem later.