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Wood Shake Roof Inspection Guide & Checklist InspectAPedia®  -     Wood shingle roof inspection checklist & wood roof inspection guidelines Roof inspection, leak detection, roof diagnosis, roof repair Key design details & references for wood shingle roofs

Here we outline key inspection points for wood or cedar shake roofs, addressing shingle type, felt underlayment, shingle exposures, wood shingle keyways or gaps, wood shingle joints, and proper wood roofing shingle fasteners, installation details and good practices. Sketch at page top is courtesy of Carson Dunlop.

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Wood Roof Inspection Checklist

The wood shingle roof inspection details outlined below are paraphrased from information provided by the Cedar Shake & Shingle Bureau, the recognized wood roofing authority since 1915 and from information provided by Carson Dunlop a Toronto company offering home inspections, home inspection publications, and home inspection education.

1. Wood Roof Leaks: Inspect inside the building for evidence of roof leaks, accessing the attic or under-roof space if it is readily accessible, and if not, inspect for indirect evidence of roof leaks such as leak stains on ceilings or at the ceiling/wall juncture of the building's highest floors.
   
   Common leak points on most roofs include at roof penetrations such as chimneys and plumbing vents and in northern climates, at the roof eaves where ice dam build-up may be a leak source.
   
   Remember to look closely for leaks below roof valleys and at roof-wall abutments where a lower roof slope abuts a higher building section sidewall.
   
   
   
   
2. Visible damage to roof shingles, flashing, or other on roof components: inspect from outside for these conditions.
   
   See Wood Roof Wear or Installation Problems for details.
   
   Also iInclude noting the presence of encumbrances such as moss on a wood roof because that material holds moisture and thus can accelerate wood roof wear.
   
   
   
   
   
   
   
   
   
3. Shingle exposures for wood roofs: the maximum weather exposure for wood shakes or wood shingles depends on the shingle size and the slope or pitch of the roof. Allowable shingle exposure may also vary by the shingle grade - something that you might infer by visual inspection of the shingles, matching against wood shingle grade definitions, or if a shingle identification label can be located.
   
   

   Roof Slope or Pitch	Maximum Wood Shingle Exposure on Roofs
   	Grade No. 1 Blue Label Shingles			Grade No. 2 Red Label Shingles			Grade No. 3 Black Label Shingles
   	Shingle Length			Shingle Length			Shingle Length
   	16"	18"	24"	16"	18"	24"	16"	18"	24"
   3/12 - 4/12	3 3/4"	4 1/4"	5 3/4"	3 1/2"	4"	5 1/2"	3"	3 1/2"	5"
   4/12 & steeper	5"	5 1/2"	7 1/2"	4"	4 1/2"	6 1/2"	3 1/2"	4"	5 1/2"

   
   
   

   Roof Slope or Pitch	Maximum Wood Shake Exposure on Roofs
   	Wood Shake Length
   	18"	24"
   4/12 & steeper roofs	7 1/2"	10" (Note)
   Note: 24" x 3/8" handsplit wood shakes are limited to 7 1/2" weather exposure, or 5" exposure where the Uniform Building Code is in application.

   
   
4. Wood shingle or shake keyways or gaps: the gap or space between adjacent wood shingles should be between 1/4" and 3/8" in width.
   
   For wood shakes the keyway should be 3/8" to 5/8" in width.
   
   The Shingle Bureau points out that the gap observed between shingles or shakes on a wood roof will vary depending on ambient moisture conditions as moist wood shingles or shakes swell (which is why we need a gap, to avoid buckling and splitting).
   
   Wood shingle keyways or gaps are illustrated at the top of this page.
   
   
   
5. Wood shingle/shake joints & gap alignment: the gaps or keyways described just above for any pair of abutting wood shingles or shakes should have a side-lap offset of no less than 1 1/2" from the joints or keyways in adjacent shingle courses (horizontal rows of shingles across the roof), and in any three shingle courses no two joints should be in direct alignment (gaps should not be over gaps in any three shingle courses).
6. Shingle type and grade identification: every bundle of wood shingles or wood shakes sold and delivered is required to include an identifying label, secured under the band that holds the bundle of shingles together. The label identifies the shingle manufacturer, a reference to model building code approval, the type of wood shingle product, and the grade of the shingle, the approving wood shingle grading agency, and the wood shingle (or shake) product's dimensions. At an older wood-roofed structure these labels may have long been thrown away, but if you are inspecting a new wood roof installation the labels should be available either on un-used shingle bundles or on occasion we've found the identifying label in piles of roof installation debris.
7. Wood shingle fasteners: should be corrosion-resistant, hot-dipped zinc-coated ("galvanized") or aluminum or stainless steel nails (or staples as allowed in some jurisdictions) and should conform to ASTM A641. Do not use blued steel or copper nails on wood roofs. Nails should be driven flush with the shingle or shake top, but not driven into (and crushing) the shingle or shake.
   
   Wood roof nails should be 3/4" (or 1" per UBC) from the shingle side edge and 1 1/2" (or 2" per UBC) above the butt line of the following shingle course (row). When inspecting an existing wood roof completely installed, do not pry up shingles to inspect the nails as you are likely to cause damage. But the nailing pattern may be visible from inside of an un-finished attic, depending on the thickness and type of roof decking. More details about wood roof nails and nailing patterns are provided at Wood Shingle Specifications.
8. Wood Shake Roof Felt Underlayment: on wood shake roofs, a 15# felt underlayment is recommended, using an 18" wide strip of roofing felt. (The Uniform Building Code specifies use of 30# felt.) The felt is placed over the top portion of the shake course at a distance above the butt equal to twice the weather exposed amount of the shake.

Carson Dunlop's sketch shows the typical cedar shake application pattern and spacing.

Here Carson Dunlop's sketch shows typical cedar shake nailing details & pattern and exposures. Notice that for this example cedar shake roof a felt interlay is installed between every course of shakes.

How long will a wood roof last?

The combination of observations about wood roof condition, leaks, shingle or shake installation quality, condition of the shingles or shakes, Wood Roof Wear or Installation Problems and Wood Roof Trouble Signs will allow an experienced inspector to estimate the "wear age" of a roof - that is, not its chronological age but the rough percent of typical life expectancy that remains for the roof. The typical life of a wood shingle roof is 30-40 years, but life expectancy varies considerably depending on the shingle quality, how the shingles were installed, on the pitch of the roof (its slope), and its sun and weather exposure. Similarly, a good quality, properly-installed wood shake roof has a life expectancy of 20-40 years.

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ROOFING INSPECTION & REPAIR
ASBESTOS CEMENT ROOFING
ASPHALT ROOF SHINGLES
BUILT UP ROOFS
CERTIFICATIONS for ROOFING CONTRACTORS
CHIMNEY INSPECTION & REPAIRS
CHOOSING A ROOFING CONTRACTOR
CLAY TILE ROOFING
FIRE RETARDANT PLYWOOD
HEAT TAPES & CABLES on Roofs for Ice Dams
LOW SLOPE ROOFING MATERIALS
MASONITE WOODRUF FIBERBOARD ROOFING
MEMBRANE & SINGLE PLY ROOFS
METAL ROOFING TYPES
MODIFIED BITUMEN ROOFING
ROOF INSPECTION SAFETY & LIMITS
ROOF VENTILATION SPECIFICATIONS
ROOF VENTING ENERGY SAVING DETAILS
SLATE ROOF INSPECTION & REPAIR
SOD ROOFING
SIDING WOOD
STAIN DIAGNOSIS on Building Exteriors
STAIN DIAGNOSIS on Roofs
STANDARDS for ROOFING
STONE ROOFING
THATCH ROOFING
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMAL MASS in UPSTAIRS
TILE ROOFING
WARRANTIES for ROOF SHINGLES
WOOD SHAKE & SHINGLE ROOFING
  Wood Roof Shingle Quality & Types
  Wood Shingle Specifications
  Wood Roof Wear or Installation Problems
  Wood Roof Inspection Guide
  Wood Roof Trouble Signs
  Wood Shakes & Application Details
  Wood Roof Protective Coatings & Fire Rating
WORKMANSHIP & WIND DAMAGE

• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• "Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
• The Cedar Shake and Shingle Bureau in the U.S.: Cedar Shake and Shingle Bureau, P.O. Box 1178
  Sumas, WA 98295-1178, or in Canada: Cedar Shake and Shingle Bureau, #2 - 7101 Horne Street
  Mission, BC V2V 7A2, 604-820-7700 E-mail: info@cedarbureau.com. The association can also be contacted by their website, cedarbureau.org where the association offers wood shingle installation instructions in the form of a manual - cedarbureau.org/installation/wall_manual/introduction.htm
• "Treatment of Cedar Shakes and Shingles," David Flickinger, RRO, Professional Roofing, October 1999, Rosemont IL.
  

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