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, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

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).

[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 Associates' sketch shows the typical cedar shake application pattern and spacing.

1. Taper-sawn wood shakes are sawn on both sides - like a thick wood shingle
2. 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.
3. 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.
4. 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 Associates' 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 there,

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.

Notes to the table above

• 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 (Steve Bliss, J Wiley & Sons) (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.]

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 (Steve Bliss, J Wiley & Sons) .

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-05-24 - by (mod) - When replacing wood shingles around the valley how many shingles are affected?

Anon

Thanks for a fair question but not one for which there is a single "right" answer.

The number of shingles to be "affected" when replacing wood shingles around a valley will vary but will certainly include:

1. all of the damaged shingles

2. if the valley is being replaced, all of the shingles that cover the valley material itself, possibly plus additional shingles to get sufficient working space to remove old and install new valley liner as well as valley itself.

3. shingles named in 1 and 2 above, for the entire length of the valley being replaced.

On 2020-05-24 by Anonymous

When replacing wood shingles around the valley how many shingles are affected

On 2018-02-20 - by (mod) - adequate nailing for wood shakes in a high-wind zone (Kansas)

TJ

Slate roof repairs have a similar problem as you cannot lift up a wood shingle, shake, nor a slate to nail below it.

See if this slate repair procedure using slate hooks would help you out.

SLATE ROOF REPAIRS

On 2018-02-20 by T.J. Stuebs

We have a client who has had some wind damage to some shake shingles in the field. Of course the insurance carrier says to break a shake out and slide another into place.

My question is : Although two nails (driven in at an angle below the existing shake) could hold the shake in place, can that shake have the ability to meet mandated uplift wind codes in Overland Park, Kansas? tj.stuebs@jrcousa.com Thank you for your opinion in advance.

Question: why is the roofing felt cut to 18" wide strips?

(Feb 27, 2015) Drue said:
Why cut the 36" roll of felt down to 18" strips in this application ?

Reply:

The roofer is interlayering a course of felt between each wood shake course.

...

Continue reading at WOOD ROOF SHEATHING, UNDERLAYMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• ALGAE, FUNGUS, LICHENS, MOSS on ROOFS
• SIDING WOOD SHINGLE INSTALLATION
• WOOD SHAKE & SHINGLE ROOFING - home
  • WOOD ROOF COATINGS & FIRE RATINGS
  • WOOD ROOF FLASHING DETAILS
  • WOOD ROOF HIP & RIDGE DETAILS
  • WOOD ROOF INSPECTION GUIDE
  • WOOD ROOF INSTALLATION SPECS
  • WOOD ROOF LIFE EXPECTANCY
  • WOOD ROOF MAINTENANCE
  • WOOD ROOF MOSS & LICHENS
  • WOOD ROOF SHAKES INSTALLATION
  • WOOD ROOF SHEATHING, UNDERLAYMENT
  • WOOD ROOF SHINGLE PROPERTIES
  • WOOD ROOF WEAR / INSTALLATION DEFECTS
  • WOOD SHINGLES, RE-ROOFING WITH

Suggested citation for this web page

WOOD ROOF SHAKES INSTALLATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

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