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Maintaining Your Roof: Non-chemical and Oil Treatments (Part 5 of Homeowner’s Guide)

Maintaining Your Roof Non-Chemical and Oil Treatments (Part 5 of Homeowner's Guide) 850x433


We have discussed the reasons you may want to apply a chemical preservative treatment to your roof. Some homeowners may not feel comfortable with the use of these chemicals, and want an alternative treatment. While non-chemical treatments are possible, their effectiveness is not known, and may not provide adequate protection. However, these kinds of treatments are worth exploring.

Non-chemical Cedar Shake Roof Treatments:

For those who prefer not to use chemicals, zinc and copper strips could be a safe and relatively inexpensive treatment to control moss and fungi, although it is not a guarantee. Zinc and copper can effectively kill and/or retard the growth of moss and fungi. It could be possible to fasten a 2 inch wide copper or galvanized metal (containing zinc) strip to either side of the ridges and run it the entire length of the roof, as well as across sections of the surface, and below the flashings (unless using copper flashings). It is believed that the rain will leach the zinc and copper from the stips, allowing them to wash across the the cedar, preventing organic growth.

I can not find any scientific study to verify the effectiveness of this technique, and it is unclear as to how much zinc and copper would be required, but I have seen some examples of its effectiveness. In one example, galvanized metal strips placed below chimney flashings appear to be effective for shingles and shakes in that area for the life of the flashings. In another case, on a roof considered favorable for moss growth, two strands of 10-12 gauge copper wire was placed on the roof (one near the ridge, and one about 15 ft. below at the halfway point on the slope), and no moss was seen to grow on the cedar. Again, while I have been unable to find any scientific data on this technique, it looks to be a promising solution for those unwilling to use chemical treatments.

Oil Treatments for Cedar Shake Roofs:

You may see oils that are advertised to replenish the natural oils in the wood. In red cedar, these natural oils account for less than 3% of the total mass. While they do contribute to dimensional stability and decay resistance, applying so-called replenishing oils to weathered shingles may be of little value, especially if they contain no preservative or water-repellent chemicals. However, you might see some temporary benefit, with regard to controlling the cupping and warping of the shakes and shingles.
In my opinion, oil treatments are very limited. Without including an effective mildewcide or other preservative, these oils, such as linseed, may actually encourage mold, mildew, and fungi growth. Furthermore, these petroleum based products oxidize in the sunlight, so they have a very short-lived benefit, and will only increase the flammability of your cedar roof. It is also worth noting that you should never stain, varnish, or seal your cedar roof. The cedar needs to breathe, and it can not do this if a stain or seal has been applied.

One Final Note:

There has been a debate among roofing contractors about the benefits of new cedar over old cedar. In my opinion, cedar is a natural wood and any natural material will be as good as the care it’s given. Your cedar roof is organic and needs to be given special care to reach its natural lifespan before being completely replaced. Just because your cedar roof is old, does not mean it needs a total replacement; most of the time, it just needs a professional cleaning and treatment.

All the information in this series of blog posts came from research from a variety of sources (most notably S.S. Niemiec, former Reseach Assistant, College of Forestry, OSU and T.D. Brown, Professor Emeritus, Wood Science, OSU), and in part from my own professional experiences. These posts are for informational and educational purposes only. While you may prefer to maintain and clean your cedar shake roof yourself, I strongly recommend you hire a professional roof cleaner.

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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