How to maintain a wood shake or shingle roof:

This article discusses the properties of wood roof shingles and shakes, including shingle grades, wood species used in roofing, and wood roof shingle or shake warranties.

This article series discusses best practices in the selection and installation of residential roofing. Our page top photo shows a wood shingle roof on the historic Mesier Homestead in Wappingers Falls, NY.

Maintenance Advice for Wood Shingle or Shake Roofs

Adapted/paraphrased with permission from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) , chapter on BEST ROOFING PRACTICES:

A number of factors affect the longevity of a wood roof. Key factors include the durability of the wood, local humidity and precipitation levels, and whether the roofing was installed with adequate ventilation.

Other factors include the slope of the roof (steeper slopes shed water faster) and the presence of overhanging trees that shade the roof and drop organic debris onto the roof, trapping moisture on the surface. Some of these factors can be controlled by the contractor; some managed by the homeowner. Others, like the weather or the reduced durability of second-growth cedar, are beyond our control.

Some simple steps that a homeowner can take to prolong the life of a wood roof include:

• Trim overhanging branches that drop pine needles or leaves on the roof.
• Clean debris out of gutters and off the roof, both the surface areas and the keyways between shakes or shingles. A garden hose can do an adequate job.
• Ensure adequate year-round ventilation of the attic or roof assembly.
• Install strips of zinc or copper at the ridge (can serve also as a ridge cap) and midway across the roof on long slopes. Runoff from these strips forms a mild solution that reduces the growth of moss, mold, and mildew. This is effective for up to 15 feet downslope from the metal.
• If moss or lichen begin to grow, scrape it away and scrub the area with a solution of 1 quart household bleach, 1 ounce detergent, and 3 quarts warm water. See details
  
  at WOOD ROOF MOSS & LICHENS.

Over time, the natural extractives in cedar and other decay-resistant species will leach out, making the wood vulnerable to decay. Also, as the shingles dry out, they are prone to cupping, checking, and splitting. At some point, it may make sense to wash and treat the entire roof.

Washing or Cleaning Advice for Wood Roofs

Cleaning wood roofs with high-pressure equipment is controversial and, in untrained hands, can cause significant damage. It is best to use normal garden hose pressure along with a brush or pump sprayer.

To remove dirt, mildew, and weathered gray residue, a consortium of wood technology and coatings experts, including the U.S. Forest Products Laboratory (FPL), recommend a solution of sodium percarbonate (disodium peroxydicabonate) and water.

With redwood and cedar, a second wash with a solution of oxalic acid may be needed to remove brown and black discoloration caused by tannins that leached out of the wood. Concentrated oxalic acid is toxic and should be handled with care.

More information: see STAIN DIAGNOSIS on ROOFS.

Preservative Treatments for Wood Shingle / Shake Roofs

There are a number of commercial treatments available to restore decay-resistance to an aging wood roof.

One effective and relatively benign (to plants) treatment consists of a copper-naphthenate compound called Cunapsol 5, which is diluted 1:4 with water and can be applied with a garden sprayer. The treatment needs to be repeated approximately every five years.

More details: see WOOD ROOF COATINGS & FIRE RATINGS.

Oil-Borne Wood Roof Preservatives

Although Cunapsol 5 and similar waterborne treatments offer good protection against mold, mildew, and decay fungi, they will not do anything to slow down the cupping and splitting caused by weathering. For that, an oil-borne treatment is required.

Effective wood roof shake or shingle preservative treatments include copper naphthenate with a 3 to 4% metal content and copper octoate with a 1 to 2% metal content. These can be brushed on or dipped (before installation) or professionally applied with spray equipment.

Semitransparent Oil-Based Preservative Stains on Wood Roofs

Semitransparent oil-based preservative stains work well on rough-textured wood, such as shakes and shingles. They provide some pigmentation and protect the roof from decay for several years. Look for a product with both a wood preservative and a water repellent.

Stains with a high percentage of pigment provide the best protection against UV degradation. While preservative stains are best applied before installing the shingles, a surface application can significantly extend the life of a wood roof.

Treatments to Use and to Avoid on Wood Shingles and Shake Roofs

According to the Shingle and Shake Bureau, one should use only products that are marketed and labeled as a cedar roof treatment, that have an MSDS available, and that contain one or more of the following: a water repellent, UV inhibitor, or U.S. EPA-registered wood preservative. The following treatments should never be used on wood shingles or shakes:

• Film-forming finishes, including paints, solid stains, waterproofers, sealants, and plasticizers
• Any product with more than 40% solvents
• Any products that contains unfortified linseed oil or diesel fuel
• Any topical treatment marketed with fire-retardant claims

-- Adapted with permission from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) .

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-05-01 - by (mod) - fire retardant wood preservative made of acrylic melamine?

Thank you for the interesting comment, Jim.

For other readers, melamine is an organic compound that when combined with formaldehyde forms a durable thermosetting plastic.

Possible formaldehyde offgassing from melamine-products

Readers will recall reports of poisoning of babies fed formula from China that contained melamine (apparently added to water as a "fake" nitrogen supplement to meet government demand for boosted production of milk). That toxic melamine additive was also found in some pet foods.

Melamine plastics in hardened form, such as countertops, are less likely to be hazardous to building occupants, though melamine dust created during working with such materials may be hazardous to workers.

And if improperly formed, wood products that used melamine can be hazardous if the product continues to offgas formaldehyde - an event that chemists ssy should not occur if the product was made properly.

For example see

• Liu, Yu, and Xiaodong Zhu. "Measurement of formaldehyde and VOCs emissions from wood-based panels with nanomaterial-added melamine-impregnated paper." Construction and Building Materials 66 (2014): 132-137.
  Abstract except:
  
  Investigation of formaldehyde and VOCs emissions from wood-based panels are of great importance because of their negative impact on human health. In this study, a novel low formaldehyde and VOCs emitting board coated with nanomaterial-added melamine-impregnated papers was developed.
  
  Melamine resins which were reinforced with nanomaterials were used to impregnate decor papers.
  
  The effect of nanomaterial type (nano TiO2, nano MMT) and loading levels (0.5%, 1%) on formaldehyde and VOCs emissions from wood-based panels with melamine-impregnated papers were investigated. Formaldehyde and VOCs measurement were conducted according to GB 17657-1999 and JIS A1901-2009.
  
  Numerical results showed that formaldehyde and VOCs emissions from coating boards were significantly affected by nanomaterials.
  

Indeed there has been a bit of research about using melamine as a wood preservative. Examples include:

Research on use of melamine as a wood preservative

• Özçifçi, Ayhan. "Effects of boron compounds on the bonding strength of phenol-formaldehyde and melamine-formaldehyde adhesives to impregnated wood materials." [PDF] Journal of adhesion science and technology 20, no. 10 (2006): 1147-1153.
  
  Vick, Charles B. "Enhanced adhesion of melamine-urea and melamine adhesives to CCA-treated southern pine lumber." Forest products journal 47 (1997): 83-87.
  
  Excerpt:
  Thermosetting wood adhesives do not adhere well enough to wood treated withchromated copper arsenate (CCA) preservatives to consistently meet rigorous standardsfor resistance to delamination in structural laminated timbers. Melamine-urea-formal-dehyde (MUF) and melamine-formaldehyde (MF) are two such adhesives. Furthermore,MUF combinations are not acceptable for bonding to CCA-treated wood under thecommercial standard ANSI/AITC A 190.1-1992.
  
  However, this study demonstrated thata hydroxymethylated resorcinol (HMR) coupling agent greatly enhances the durabilityof adhesion, particularly resistance to delamination, of both types of adhesives inradio-frequency-cured lumber laminates of CCA-treated southern pine.
  
  Although neither adhesive quite met delamination requirements in these tests, it appears that properlyformulated MUF and MF adhesives could meet requirements of the qualifying standardASTM D 2559 on HMR-primed CCA-treated wood.
  
  You can read tne entire paper at inspectapedia.com/roof/Melamine-wood-preservative-USFPL-Vick.pdf
• Tomak, Eylem D., Ergun Baysal, and Huseyin Peker. "The effect of some wood preservatives on the thermal degradation of Scots pine." Thermochimica Acta 547 (2012): 76-82.
• Gindl, W., F. Zargar-Yaghubi, and R. Wimmer. "Impregnation of softwood cell walls with melamine-formaldehyde resin." Bioresource technology 87, no. 3 (2003): 325-330.
• Hirata, Toshimi, Mamoru Inoue, and Yasuo Fukui. "Pyrolysis and combustion toxicity of wood treated with CCA." Wood Science and Technology 27, no. 1 (1992): 35-47.

Toxicity of Melamine in Some Products & Materials

Watch out: though there is some research arguing the opposite view, there is evidence that in at least some environments melamine can be highly toxic, possibly carcinogenic.

See:

• Hau, Anthony Kai-ching, Tze Hoi Kwan, and Philip Kam-tao Li. "Melamine toxicity and the kidney." Journal of the American Society of Nephrology 20, no. 2 (2009): 245-250.
• Yin, Rong H., Xin Z. Wang, Wen L. Bai, Chang D. Wu, Rong L. Yin, Chang Li, Jiao Liu, Bao S. Liu, and Jian B. He. "The reproductive toxicity of melamine in the absence and presence of cyanuric acid in male mice." Research in veterinary science 94, no. 3 (2013): 618-627.
• Chu, C. Y., and C. C. Wang. "Toxicity of melamine: the public health concern." Journal of Environmental Science and Health, Part C 31, no. 4 (2013): 342-386.
  Abstract:
  Melamine contamination in food has resulted in sickness and deaths of human infants, pets, and farm animals in the past decade. The majority of the victims suffered from acute kidney injury, nephrolithiasis, and urolithiasis.
  
  Since then, animal studies have revealed the possible target organs of the melamine toxicity and the extent of the adverse effects of the contaminant. State-of-the-art analytical methods have been developed to achieve the “zero tolerance” aim for such economically motivated adulteration.
  
  These studies provide in-depth understanding of the melamine toxicity and promising analytical methods, which can help us safeguard our dairy food source.
  

On 2020-04-30 by Jim

We had good luck with a fire retardant wood preservative that was made in Texas. It consisted of acrylic melamine, and as such was a UV protectant.

Unfortunately, the company went out of business when the owner had a heart attack. We did some of the best shake roofs in California.

On 2019-11-09 - by (mod) - How can I know when individual wood shingles need maintenance or replacement?

Nate:

Some examples of wood shingle or shake damage that you might see from the ground with binoculars or from closer inspection include

- shingles missing entirely

- cracked or split shingles, particulary if the crack or split is within 1 1/2 or 2" from the butt joint of the pair of shingles below the one inspected

- wood shingles that are worn thin, curling

- rotted (rare) shingles

- leaks seen from the attic side

On 2019-11-08 by Nate

How can I know when individual shingles need maintenance or replacement?

TY

On 2018-03-02 by spike

how do I find cypress shakes
also whats the best product to clean a very old wood shake roof.
also , how do I know when the roof is beyond repair?
its a show piece , its not lived in
its in a park
its very old

On 2017-09-2 - by (mod) - wood shingle roof treatment applicable with a garden sprayer

Dave,

I would check out the wood treatments discussed in the article above and then I would go take a look at

WOOD ROOF COATINGS & FIRE RATINGS

On 2017-09-24 by davek1243@gmail.com

Hello,
I live in CT and have a cedar wood shingle roof. Can you recommend a product that would be sprayable with a garden type sprayer and available at Home Depot, etc.? Thank you very much.

On 2017-07-14 by Chris

What chemical to treat roof wood shingles for fungi, mold & moss.
Which oil to use to restore wood shingles

...

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