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Top Tips for Cleaning Moss From a Cedar Shake Roof

How To Deal with Green Moss on Cedar Shake roof?


In this article, we will discuss why cleaning moss from a cedar shake roof is important.

Moss growth can create several problems on shake roofs. While a small layer of thin moss isn’t as troublesome, large clumps of moss can degrade shakes, get beneath them, and create opportunities for leaks. Further, many of the methods of removing moss recommended online actually damage the shakes, which could significantly increase your odds of getting a leak. So, how do you safely remove moss from a shake roof? How do you prevent moss from growing back after you have removed it? I’ll answer those questions and tell you other things you need to know about handling the moss on your shake roof.

Top Tips for Cleaning Moss From a Cedar Shake Roof

Table of Contents

Why is Moss Bad for Shakes?

You may feel that a bit of moss gives your roof some charm, just as ivy growing up the side of your house might. While moss may be beautiful, it is a detriment to your roof. Here’s why:

Most plants gather water from their roots, but mosses gather water from their leaves. Therefore, they do not mind that shake, unlike soil, are a dry and relatively nutrient-free environment. They will grow roots directly into the shakes, destroying the shakes and creating the opportunity for leaks.

When it rains, moss will soak up water and retain it, creating consistently wet conditions on your roof. Moss growth will also interfere with the proper drainage of water off the roof as water needs to trickle through or around the moss instead of running straight down to the gutters. The resulting constant exposure to water can degrade shakes.

Over time, moss can also work its way under shakes, lifting them. This uplift creates opportunities for water to penetrate lower layers of the roof and, potentially, your home.

While minor moss infestations may appear not to cause many issues, it is likely to become severe over time. Once you spot moss growth on your roof, you should take steps to resolve it. If you have a severe infestation, you may have no choice but to remove the shakes that have been damaged by it. A professional roof cleaner can help you assess what kind of intervention your roof needs.

What if the Moss Appears Dead?

If the weather has been consistently dry, moss may appear to be dead. However, some species of moss can stay alive when dried out for months. All it will take is one rain for it to recover and continue growing. If your moss has dried out, take the opportunity to have a roof cleaner remove the moss from the roof.

How To Remove Moss from a Roof

Here is a video on how to remove moss
Play Video about Roof Cleaning How to Remove Moss, Lichen, Fungi from a Cedar Roof Sullivan Roof

If your roof has sprouted a moss infestation, you can remove it before it becomes serious enough to impact the performance of your roof. Moss is tough, and typically you will not be able to pull it by hand. However, you can use a chemical solution to loosen the moss without damaging the shakes. I don’t recommend that you step on the roof for moss removal.


Step One

Safely set up your ladder near the moss. Use a ladder with a standoff on it to raise you above the roof. With either your homemade cleaner or a store-bought option, spray the moss. I use a citrus-based cleaning solution that I developed myself.


Step Two

If using a homemade spray, leave it on for 15-20 minutes. Note: Though there are several store-bought solutions, I have found them not to be very effective.


Step Three

Using your garden hose on low pressure, rinse the moss thoroughly. You should find that most of the moss will come off from the spray of the water. Be sure not to direct a pressurized spray beneath the shakes. Otherwise, you could create a leak. It is not necessary to remove all the solutions. I always leave some of the answers in my process because I use a steam process oil to help rehydrate the shakes.


Step Four

You may find it hard to remove all loose moss. Don’t concern as a good rain will rinse such down your roof. Now either rinse out your gutters or clean them by hand.

Methods You Should Not Use When Cleaning Moss From a Cedar Shake Roof

Unfortunately, there is a lot of bad advice out there about how to remove moss. While these methods may appear effective at removing moss, they can also damage shakes in the process. I don’t recommend you try to clear your moss by:


You may be tempted to scrub the moss off the shingles because moss grips shingle pretty strongly. However, scrubbing is likely to damage the shakes.

Pressure Washing

Pressure washers can be powerful and undoubtedly strong enough to break shakes and lift them. Any amount of pressure washing can cause severe problems with the roof, including significant leaks. Never use a pressure washer or a pressurized stream of water on your roof.

Using Harsh Chemicals

High concentrations of bleach and other chemicals may do permanent damage to the shakes, increasing your risk for leaks. However, small amounts of bleach/pool chlorine are very effective at killing bacteria.

If you’re in doubt about the safety or effectiveness of a moss removal method you want to try, consult with a professional roof cleaner.

How To Prevent Moss on Your New Roof

Here are a few ways to prevent moss growth on your roof:

Remove Sources of Shade

Moss prefers to grow in the shade, so exposing more of your roof to sunlight will help deter it. It would help if you considered trimming trees that shade out the roof or moving garden features, like pergolas or trellises, so that they do not cast shade on the roof.

Algaecide and Fungicide

Where there’s moss, there is also algae and fungi, as they thrive on the same wet and shady conditions. You can lessen algae and fungi infestations by using an algaecide and fungicide within the cleaning solution.

Cleaning and Treatment

Every cedar shake roof should be cleaned and treated every 7 to 10 years. Cedar shakes are organic and need to be maintained.

Get Regular Inspections

Roof cleaners can often prevent moss growth by ensuring that your roof is draining water properly. They should inspect and clean your gutters yearly to avoid the backup water that could attract moss.

What if the Moss Grows Back?

You should not see moss return between cleanings if you have trimmed back surrounding tree cover and avoided shade on the shake roof. If the moss returns and you did the cleaning, you should contact a roof cleaner that has experience with cedar shake roofs. If cleaned and treated correctly, moss should not return.

Do You Need Help Dealing with Moss?

Bruce Sullivan is the owner of Sullivan Roof Cleaning, Inc., with over 50 years of cleaning, maintaining, and restoring cedar shake roofs. Contact Bruce today and get a quote for your roof.

Cedar Shake Roof Cleaning in Des Moines Iowa
Cedar Shake Roof before & after cleaning

Meet Bruce

50 Years of Experience &
Over 2,000 Shake Roofs Cleaned

Bruce Sullivan has over 50 years of experience in maintaining, cleaning, and restoring cedar shake roofs. Making him one of the top authorities on cedar shake roofs in the US.

Watch the Cedar Shakes Cleaning Process in Action in this video

Play Video about Roof Cleaning How to Remove Moss, Lichen, Fungi from a Cedar Roof Sullivan Roof


What can I say? Bruce and Keith provided an exceptional service, and they are really nice guys too. Found out at the last minute they were in Minneapolis, and they fit me in for a cedar shake roof cleaning the next evening after their regular job was done. Even cleaned up my gutters, small fence, and small deck at no charge. The place looks outstanding! Highly recommended.

Mike Richards

I highly recommend this business. Due to the work performed we are going to get another 10-14 years out of our cedar shake roof. We were told by some roofing companies that the roof should be replaced in 2 years. I lucked out and found Sullivan Roof Cleaning while researching companies that perform this service, and was pleased to learn that the company does work outside of Iowa. If you need your cedar shakes cleaned, go with Sullivan Roof Cleaning.

Eric Oelrich, 
St Cloud, MN

Bruce did a great job cleaning the whole exterior of my house. The roof has new life! It looks practically brand new. All the mold and moss on the roof, on the gutters, under the eaves, completely gone. He exceeded all our expectations. When he tells you what he can do for your house, you can believe and trust him. Great guy, great service.

Stuart Malone
Kansas City, MO


Cedar shakes are organic. Though a resilient material. Being organic they need to be maintained. Over time, like any organic material that are subjected to weather elements, they reach a stage of deterioration. Like UV exposure, moisture and seasonal changes. Which results in moss, mold, mildew, lichen and brown rot fungi. These infestations need to be removed to further preserve the integrity of the cedar shake.
The proper way to clean a cedar shake roof is from a ladder. By spraying a special formulated solution onto the shakes and then rinsed with a garden hose pressure. Best done by a professional cedar shake roof cleaner. Not DIY recommended.
No. Pressure washer will require walking on the shakes, which will harm them, and even at its lowest setting will also damage the shakes.
On average, cedar shakes should be cleaned every 10 ten years. Subjective to the grade of the shakes and the amount of surrounding tree cover.
Avoiding walking on a cedar shake roof, other than for repairs.
Never seal a cedar shake roof. Cedar shakes need to breathe. They expand and contract in rain conditions. Seal will shorten the lifespan, to the point of premature replacement.
Staining has no real preserve value and can also harm the integrity of shakes, as stated, they need to be able to breathe. Also, if the shakes are not properly cleaned staining can seal the deteriorating infestation within the shakes.
Depending on the grade of the shakes and installation, and if maintained properly, 40 to 60 years.


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