Chinook Roofing Blog

What You Need to Know About Moss Growth on Cedar Roofs

Posted on: July 20, 2016

Moss_photoCedar roofing is a popular investment for homeowners. Many people choose cedar roofs because of the wood’s natural beauty and appearance. Cedar roofing is a great way to blend your home with surrounding nature. Cedar roofs also provide excellent protection from inclement weather, such as hail or wind.

Despite the many benefits that cedar roofs offer, they also have limitations, such as problematic moss growth. Fortunately, homeowners can prevent and treat moss growth to preserve the life of their cedar roofing.

Here are some answers to common questions you may have about moss growth on your cedar roof.

What Are Some Ways to Prevent Moss Growth?

Homes that are heavily shaded or in warm, humid climates tend to experience moss growth more often than homes in dry climates. Cedar roofs require constant airflow to stay dry, especially if you live in an area that experiences heavy rain. Without dry air, the moisture will attract fungi or moss growth.

You can reduce moisture on your roof by clearing debris, such as pine needles or leaves. These types of debris will often trap moisture on the cedar roofing.

You can also promote a dry roof by removing any tree branches that may shade sections of your roof. Similarly, you should never allow branches to rub against or touch the roof’s surface because they typically block the airflow.

Zinc and copper have also been commonly used to prevent moss growth on cedar roofs. Some professionals recommend applying copper ridge flashing to prevent moss growth.

Others may recommend installing zinc strips on your roof. The strips are typically two inches of zinc metal installed evenly over the surface of the roofing. They release zinc molecules that prevent moss growth after rain.

How Do I Treat Moss Growth?

If you notice moss on your roof, there are a few ways to remove the growth. Keep in mind that cedar roofs require different treatments for moss growth than asphalt, slate, metal, or tile roofs. Cedar requires special cleaning because it often experiences different types of organic growth. Additionally, the moss treatment must not damage the cedar material.

Some moss or fungi growth you may notice are dark, brown or black patches that deteriorate shakes or shingles. These types of organic growth will deteriorate cedar roofs faster than most other roofing complications.

If you notice moss or fungi growing on your roof, call a professional to clean it off. Expert roof cleaners can use a high-pressure washer to clear the growth from your roof. After cleaning the moss, a professional may apply water-based sealing oil. This preservative replaces the cedar’s natural oils that may have leaked out over time and prevents future moss growth.

When Should I Start Moss Prevention and Treatments?

If you live in the Pacific Northwest, do your best to begin moss prevention before autumn rains start. During this time, consider hiring a professional to clean moss from your roof. Cedar roofs respond best to moss cleanings when the temperature is consistently above 50 degrees. This temperature allows the cedar material to thaw and release infestations properly.

You may need to use preservative treatments throughout the year if you live in an area with persistently warm, humid temperatures. Seek moss treatment from a professional every six to eight years to ensure that your cedar roof lasts its full lifespan. With proper treatment, your cedar shakes or shingles should last between 40 and 60 years or longer.

What Happens If I Don’t Clean Off the Moss Growth?

Wood naturally absorbs water. When homeowners don’t hire a professional to clean the moss off of their roofs, the moss increases the amount of moisture that makes contact with the cedar roof. If left untreated, this moss growth can rot or decay the cedar wood on your roof.


If you notice moss growing on your cedar roof, contact Chinook Roofing & Gutters. Our professionals can assess the moss damage and determine the best treatment options for your roof.


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The only thing better than our new roof is the company who installed it. Kind and capable people from the inspection and estimate to impeccable clean up. Thank you so much!