Types of Wood Cedar Shake Roof Application Pattern Details
Unlike their thinner brothers, wood shakes are typically 18"to 24" in length, and up to 14" in width (more than 8" is at extra risk of future splitting).
[Click to enlarge any image]
The roofing shake thickness ranges from 1/2" to 1 1/4" where measured at the shingle butt. The maximum exposure for wood shakes is 7 1/2" (for an 18" long wood shake) or 10" (for a 24" long wood shake), and head lap is 3" or 4" respectively.
A good quality, properly-installed wood shake roof has a life expectancy of 20-40 years. Carson Dunlop's sketch shows the typical cedar shake application pattern and spacing.
Taper-sawn wood shakes are sawn on both sides - like a thick wood shingle
Taper split wood shakes are cut from opposing ends of a wooden block, having a shake butt that is at least 1/2" in thickness and typically are 24" in length. Uncommon, costly.
Hand split, re-sawn wood shakes are similar to straight split shakes (below) but are thicker. A thick split of wood that is rough-split on both sides is re-sawn in half through its thickness to produce two thick shakes, each with a smooth back.
Straight split wood shakes (also called barn shakes ) are split from the same end of a block of cedar (or other wood) and are not tapered. Straight split wood shakes are not usually used on homes.
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.
Wood shake exposures for wood shake 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 wood shake exposure may also vary by the shake grade - something that you might infer by visual inspection of the shakes, matching against wood shake grade definitions, or if a wood hake identification label can be located.
Roof Slope or Pitch
Maximum Wood Shake Exposure on Roofs
Wood Shake Length
4/12 & steeper roofs
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.
Wood shake keyways: 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.
Wood shake joints & gap alignment: the gaps or keyways described just above for any pair of abutting wood shakes should have a side-lap offset of no less than 1 1/2" from the joints or keyways in adjacent shake courses (horizontal rows of wood shakes across the roof), and in any three wood shake courses no two joints should be in direct alignment (gaps should not be over gaps in any three shake courses).
For added details about proper wood shake roof installation, the most authoritative source of wood shingle and wood shake information is from the Western Red Cedar Shingle & Shake Bureau (now the Cedar and Shake Shingle Bureau, since not only western red cedar is used for roof shingles).
Wood Shake Roof Installation Specifications - Best Practices
Whether installed over spaced or solid sheathing, shakes
should always be interlaid with 18-inch-wide strips of
No. 30 roofing felt. The felt strips acts as baffles to keep
windblown snow and other debris from penetrating the
roof system during extreme weather. The felt “interlayment”
also helps shed water to the surface of the roof.
important to locate each felt strip above the butt of the
shake it is placed on by a distance equal to twice the
weather exposure (Figure 2-51 shown below).
[Click any image or table for an enlarged, detailed view.]
Placed higher, the felt strips will be ineffective. Placed
too low, they will be visible in the keyways and will wick
up water, leading to premature failure of the shakes. In
addition, follow these guidelines:
For the starter course, use either a single layer of shakes
or two layers separated by a strip of felt interlayment
(installed up from the eaves by a distance equal to the
weather exposure). Fifteen-inch shakes are available
for the bottom layer of a double starter course
Each shake gets two nails about
inch in from each end
inches above the butt line of the overlaying shake.
The first course should overhang the fascia by
All courses should overhang the rake trim by about
Leave a gap between adjacent shakes of
expansion when wet.
Offset joints in successive courses by at least 1
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(Feb 27, 2015) Drue said:
Why cut the 36" roll of felt down to 18" strips in this application ?
The roofer is interlayering a course of felt between each wood shake course.
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"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.
Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
Cedar Shake & Shingle Bureau, CSSB, U.S.: Sumas, WA 98295-1178, Tel: 604-820-7700, In Canada:
Cedar Shake and Shingle Bureau #2 - 7101 Horne Street, Mission, BC V2V 7A2 Tel: (604) 820-7700, E-mail: email@example.com , website: http://www.cedarbureau.org/
CCSB offers wood shingle installation instructions in the form of a manual - cedarbureau.org/installation/wall_manual/introduction.htm
Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. The text covers moisture needs, heat tolerance, hardiness, bloom color, foliage characteristics, and height of 350 species and cultivars.
Green Roof Construction and Maintenance, Kelley Luckett, McGraw-Hill Professional, 2009, ISBN-10: 007160880X, ISBN-13: 978-0071608800, quoting: Key questions to ask at each stage of the green building process Tested tips and techniques for successful structural design
Construction methods for new and existing buildings
Information on insulation, drainage, detailing, irrigation, and plant selection
Details on optimal soil formulation
Illustrations featuring various stages of construction
Best practices for green roof maintenance
A survey of environmental benefits, including evapo-transpiration, storm-water management, habitat restoration, and improvement of air quality
Tips on the LEED design and certification process
Considerations for assessing return on investment
Color photographs of successfully installed green roofs
Useful checklists, tables, and charts
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