How to Clean Moss Off Fiberglass Roof Panels

Moss grows in some of the most inconvenient places, such as on a fiberglass roof. Removing moss from the fiberglass shingles or panels is essential to the roof's integrity. The moss's roots can penetrate underneath the shingles, loosening them from the tar paper. Moss also holds moisture, which can freeze, thaw and refreeze repeatedly during cold weather, further compromising the roof. It is essential, therefore, to remove the moss from your fiberglass panels before it spreads and becomes a major and expensive issue.

Step 1

Select a cleaner that removes or kills moss on fiberglass asphalt shingles.  If it states it removes algae, it will also work on moss.

Cleaners made with an oxygen bleach may be more environmentally friendly than other products.  For easy use, select one with an applicator built in.

Otherwise, you will need a pump sprayer.  You will also have to dilute the cleaner according to the manufacturer's directions.

Step 2

Spray the product on the roof as directed on the label.  This is best applied in the spring or fall, according to Popular Mechanics.

After the moss dies, which can take a week or more, proceed to the next step.  You may need to reapply the product, however, if some of the moss is still alive.

Step 3

Spray a pressure washer to remove the dead moss.  Start at the top of the roof, pointing it down toward the ground so you don't spray water up and under the fiberglass shingles, causing a leak.

Begin with a low setting, holding it at least 12 to 24 inches away.  Increase pressure and hold the wand closer as necessary, being cautious not to damage the fiberglass panels.

The power washer will loosen and wash away the moss from the roof. 

Things You Will Need

  • Moss cleaner
  • Applicator or pump spray
  • Power washer


  • Prevent moss from growing again. Several products are sold for this purpose. For example, certain sprays applied to the roof once a year inhibit moss and algae growth. Alternatively, you can install zinc or copper strips on the roof ridge. These strips release chemicals when it rains that minimize moss growth.


  • Since climbing on the roof is required, only those in good physical condition with the ability to maneuver up to the roof and stay steady should complete this task. Be especially careful when moving around a wet roof.

About the Author

Melissa Lewis is a former elementary classroom teacher and media specialist. She has also written for various online publications. Lewis holds a Bachelor of Arts in psychology from the University of Maryland Baltimore County.