Cedar shake nailing pattern (C) Carson Dunlop

Wood Shake Roof Installation Details - Photo Guide

WOOD ROOF SHAKES INSTALLATION - Wood shingle roof inspection, failures, repair, product defects
- Roof inspection, leak detection, roof diagnosis, roof repair
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Questions & Answers about specifications for installation of wood shakes on roofs
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Wood shake roof installation details: here we define wood or cedar shake roofing materials & we discuss wood shake roofing installation details and good practices. Sketch at page top is courtesy of Carson Dunlop Associates. Also see WOOD ROOF INSTALLATION SPECS and see our checklist of wood shingle installation specs at WOOD ROOF INSPECTION GUIDE.

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).

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.

More details useful for determining the condition of a wood roof are at WOOD ROOF INSPECTION GUIDE.

As we also discuss at WOOD ROOF INSPECTION GUIDE,

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
	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.

Shingle exposure rules for wood shingles (as opposed to shakes) are detailed at WOOD ROOF INSTALLATION SPECS.

Wood shingle or shake keyways or gaps

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

As detailed in Best Practices Guide to Residential Construction (printed text) chapter on BEST ROOFING 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.

It is 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.]

Figure 2-51: Wood Shake installation details (C) J Wiley, S Bliss

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 3/4 inch in from each end and 1 1/2 inches above the butt line of the overlaying shake.
The first course should overhang the fascia by 1 1/2 inches.
All courses should overhang the rake trim by about 1 inch.
Leave a gap between adjacent shakes of 3/8 to 5/8 inch for expansion when wet.
Offset joints in successive courses by at least 1 1/2 inches

-- Adapted with permission from Best Practices Guide to Residential Construction.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
"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.
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
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: info@cedarbureau.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
"Treatment of Cedar Shakes and Shingles," David Flickinger, RRO, p. 74, Professional Roofing, NRCA, October 1999, Rosemont IL.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
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
Handbook of Building Crafts in Conservation, Jack Bower, Ed., Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of Congress Catalog Card Nr. 81-50643.
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Wood Shingle Roofs, Care and Maintenance of wood shingle and shake roofs (EC), Stanley S. Niemiec (out of print)
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