Material and system description
Wood shakes and wood shingles are manufactured from western red cedar, cypress, pine and redwood trees. Shakes are split from logs and reshaped by manufacturers for commercial use. They are thicker at the butt end than shingles; generally one or both surfaces are split to obtain a textured effect. A split and resawn shake has a split face and sawn back. A taper sawn shake has a natural taper and is sawn on both sides. Wood shingles are sawn on both sides and have an even taper and uniform thickness. When applied to shingles, the industry terms "Perfection" and "Royal" mean 18 inch and 24 inch lengths, respectively.
Cedar shakes and cedar shingles are available pressure treated with fire retardants and chemical preservatives for increased fire resistance and to prevent premature rot and decay in some climates.
Pine shakes are made from southern yellow pine and are taper sawn. They also are available pressure treated with preservatives to protect against decay and insects. Interlayment felts are required for pine shakes.
Wood roof systems may be applied over continuously or closely spaced wood decking or over a spaced, sometimes referred to as "skipped," sheathing. Solid roof decking or sheathing should be used in areas of the roof deck where an ice dam protection membrane is required.
The most common materials used for roof decks are plywood or oriented strand board (OSB). When plywood is used, NRCA recommends the use of a minimum 15/32 thick or 1/2 inch nominal exterior-grade plywood for 16-inch rafter spacings and 5/8 inch nominal thickness for 24-inch rafter spacings. For OSB, NRCA recommends a minimum 15/32 inch thick or 1/2 inch nominal exterior-grade OSB for 16-inch rafter spacings.