Note: This is cleaning/treatment/restoration only. We do not offer roof repair services.
Cedar Site Logo

Cedar Shakes Roof Cleaning Explained


In this article, on “Cedar Shakes Roof Cleaning Explained” we are going to break down the underlay and what it is, and then the cedar shakes and shingles.

A cedar shake roof is made up of several parts, you have the initial framework of the house and all the support beams and battens and then there is the felt underlayment.  This can be referred to as felt underlay or felt underlayment, it can also be referred to as Tar Paper.  Sometimes there is a synthetic underlayment that is used but this is not as common on older cedar shake roofs, so for the purposes of this article, we will stay with felt underlayment. If you wish to learn more about synthetic underlayment and the differences between the two you can do so in our article on “What goes under a cedar shake roof?“.

Felt Underlayment/ Tar Paper

Felt Underlay

The thing we will look at is the roofing felt. Roofing felt is incredibly important, it is a tar paper barrier that goes underneath your cedar shakes and it keeps the main roof structure dry. Felt paper is the very first layer of the roof and protects the structure and main body of the house, without it, the water would pass the outer cedar shakes and go directly onto the frame supporting the roof causing it to become damp and rot.

Felt paper can last for decades, as you can see it in the video.

How do I know if the Felt is ready to be Replaced?

When felt underlayment is aged and ready to be replaced you will see that it begins to crack, loses its flexibility, and becomes brittle and stiff.  These are key signs that the felt underlayment is aged and ready to be changed.  If it is not changed then you will likely encounter leaks and water penetrating into the interior of your house itself.  Maintaining the exterior cedar shake roof plays a vital role in the condition of the felt underlay.  If the shakes are in poor condition more water will penetrate in and cause a more rapid deterioration of the underlay.

Felt Underlayment Cracking

How to Replace the Felt Underlayment?

Replacing the felt underlay requires some effort as the cedar shakes will need to be removed in order to access the felt below.  If you are looking to replace the felt underlayment of your roof, you are essentially looking at a roof replacement.  If the cedar shakes on the exterior are tired, mold infested, fungus covered, and lost in algae then the shakes will need either a good cleaning in order to restore them or to be replaced.  The course of action to be taken will depend on the condition and any input given by a cedar shake professional.

A man spraying a roof with a hose.

What Can I Do to Prevent The Deterioration of the Felt Underlayment?

Maintaining the cedar shake roof is an important part of protecting the felt beneath. If the cedar shakes are clean, healthy, and working as they should be then they will protect the felt underlayment. Essentially, keep the cedar shakes in good condition and you will keep the felt in good condition.

Maintain The Health of Your Cedar Shakes and Shingles

How to Maintain Your Cedar Shake Roof?

The best way to maintain your cedar shake roof is by removing moss, algae, fungi, and organic debris, repairing broken shakes or warped shakes and making sure that your roof doesn’t become too saturated with water. If you notice an area on the roof is looking infested, damaged, or continuously wet then you must take immediate action. Call a professional cedar shake roof cleaner to assess the situation and remove and resolve the problem.

If your cedar shake roof has moss, fungus, algae, or other organic matter and growths, this is causing the roof to deteriorate and will result in a premature replacement of the roof.

Bruce Cleaning the Roof From Ladder

How Can I Tell if My Roof has Infestations?

You should be able to see growth and organic matter on the roof if it is not in optimal condition. If you can see a slight discoloration to the shake or shingle roof then this is likely a natural process called weathering, but if there is any visible organic matter on the roof then this would need care and attention.  If in doubt get a professional opinion and request a quote from Bruce.

What Problems Does it Cause?

There are several issues that you may encounter on your cedar shake roof such as moss, algae, fungus, and brown rot.

Moss covered Cedar Shingle

Moss – A green moss-covered roof may look rustic and like a fairy tale but sadly it is actually causing damage to the roof and will damage the shakes as moisture is trapped and the shake deteriorates. Cedar Shakes are naturally resistant and will look after themselves for years, it is only when trapped moisture comes into play that they will begin to rot and break down. Moss is typically seen on the north, north-west side of the house, especially if there are trees and tree overhangs.

Making sure to get the moss removed from your roof should be important when considering your cedar shake roof maintenance.

Algae – Algae is another organic substance that you may find on your cedar shake roof and it is particularly dangerous as it spreads like wildfire. You will notice that algae staining occurs with water and moisture and the greener the stain, the more infestation has occurred.  As with moss this is important to get remove in order to maintain the health of your cedar shake roof.

Fungus – Fungus is another problem that you may have on your cedar shake roof. If there are infestations of fungus then the shakes will break down faster than normal. The organic matter provides a great environment for fungi to thrive and it will cause damage to or complete destruction of the shingles or shakes.

Cedar shake fungus can be seen on many roofs and it is important to be removed.  Many people just assume this is a normal part of the roof when in fact it is not.

A man holding a piece of wood in front of a house.

Brown Rot – Brown rot looks like small pinholes in your cedar shakes or shingles. It is extremely dangerous as it allows water in and the wood will quickly begin to rot if this is not resolved.  The condition will rapidly get worse the longer it is left.  Along with the aforementioned infestations that can aflict a beautiful cedar shake roof, brown rot needs to be addressed and removed.  Contact Bruce today and get a free quote for your cedar shake roof.

What Can Sullivan Cedar Shake Roof Cleaning Do?

Bruce Spraying Formula onto Cedar Shake

The Sullivan Cedar Shake Roof Cleaning solution will remove all these infestations and restore your cedar shake back to how it should be. Our solution is safe for you, your family, your pets, and the cedar shake roof. There are no dangerous chemicals that will adversely affect health or the surrounding environment.

By spraying the solution onto the shake the organic infestations will start to dislodge and remove, after about 10 minutes of soaking it is then ready to be rinsed with the pressure of a garden hose. The solution will remove all damaging organic matter and the causes, it is important to remove the cause otherwise the infestation will return in no time at all.

When we remove the cleaning solution it is important to never use a pressure washer or anything more powerful than a standard garden hose. This is incredibly important as you will damage the roof with the high-pressure water, damage and break the shakes and cause more issues than you started with.

As you can see the old shake, cleaned shake, and a new shake, the cleaned shake still has a contrast to the new shake but is remarkably different from the old shake.

Rinsing Cedar Shake with Water
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.


Free No Obligation Estimation

Recent Posts

Free No Obligation Estimate