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.
Wood roofing may be attached to a roof deck with noncorroding, galvanized steel or stainless steel nails or noncorroding metal staples. A minimum of two fasteners should be used to attach each shake or shingle. Nails should be long enough to penetrate through all layers of roofing materials and extend through the underside of the roof deck or penetrate at least 3/4 inch into wood plank or board decks.