After a roof is cleaned, a preventive treatment can be applied to help slow how quickly algae or moss returns, extending the time between cleanings. This isn't a permanent solution but can meaningfully reduce regrowth speed on roofs prone to recurring buildup.

  • Applied after cleaning to slow regrowth
  • Extends time between full cleanings
  • Best suited for roofs with a history of recurring algae or moss

Keep in mind: If your roof hasn't been cleaned yet, start with soft wash cleaning first -- preventive treatment works best as a follow-up step, not a substitute for actual cleaning.

Preventive Algae Treatment FAQs

Do zinc or copper strips keep roof algae from coming back?

They can help. Rain washes small amounts of zinc or copper down the roof from strips installed near the ridge, and those metals inhibit algae growth. Results are best directly below the strips and fade farther down large roof planes, and the strips work better as prevention after a cleaning than as a way to remove existing streaks. Many newer shingles also include algae-resistant granules. On shaded, north-facing slopes where algae grows fastest, strips or a periodic preventive treatment can extend the time between cleanings.

This content is reviewed by the Des Moines Roof Cleaning editorial team and informed by licensed-contractor sourcing, manufacturer documentation, and established industry standards for Roof Cleaning. Read our editorial standards.