Wood shingle roof, Wappingers Falls NY (C) Daniel Friedman Wood Roof Shingles & Shakes Maintenance Guide
     

  • WOOD ROOF MAINTENANCE - CONTENTS: Cleaning & maintenance advice for wood shingles & shakes on roofs. How to wash or clean wood roofs. Guide to using preservatives on wood shingles or wood shakes. Treatments to use & others to avoid using on wood roofs
  • POST a QUESTION or READ FAQs about how to maintain, coat, or clean wood shingle & wood shake roofs
  • REFERENCES

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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.

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Maintenance Advice for Wood Shingle or Shake Roofs

Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, 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.

 

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