Wood Shake Installation

Wood shakes are split (rather than sawn) wooden roofing units, usually of western red cedar in North America. Because a shake's split face is rough and the pieces do not lie tightly together, shake roofs normally use an interlay of roofing felt between courses to stop wind-driven rain and snow from passing through the gaps. Shake installation details are published by the Cedar Shake and Shingle Bureau (CSSB) and in building codes and national roofing manuals.

Underlayment and interlay

Canadian guidance starts with a 1 m (39 in) strip of No. 30 felt at the eave. Each course then receives an interlay strip of No. 30 felt 450 mm (18 in) wide, placed above the shake butts at a distance equal to twice the exposure, so the lower part of the felt is covered by the shakes of the next course. The CSSB warns that felt should not be visible in the gaps between shakes, because sunlight degrades it.

Spacing and offset

• Keyways. Shakes are spaced with a gap between adjacent pieces to allow swelling. The Cedar Shake & Shingle Bureau specifies a gap of 3/8 to 5/8 in (10 to 16 mm) between shakes. The CSSB notes that keyways should never be caulked.
• Side lap. Joints are offset at least 38 mm (1 1/2 in) from those in adjacent courses, and no two joints should line up in any three courses.

Nailing

Canadian guidance specifies two nails per shake regardless of width, about 25 mm (1 in) in from each edge and about 50 mm (2 in) above the butt line of the following course. Nails must be corrosion resistant; the CSSB requires Type 316 stainless steel fasteners for fire-retardant or preservative-treated shakes.

Exposure

Shake length	Max exposure, standard (Canada)
600 mm (24 in)	250 mm (10 in)
450 mm (18 in)	189 mm (7 1/2 in)

Shakes are typically used on slopes of 4:12 or steeper. Exposure must not be exceeded, since that reduces the overlap.

Deck

Shakes can be laid on solid sheathing or on spaced boards that allow air to dry the underside. Ridge and hip caps are made from overlapping pairs of shakes with alternating joints.