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| Preparing a Roof for Wood Shingles or ShakesWood shingles and shakes usually are made of Western red cedar, a long-lasting, straight-grained wood. The grain is what gives the wood surprising strength whether it is cut thick or very thin.
Even after years of weathering, wood does a much better job of shedding water than might be expected. In addition, wood shingles and shakes resist heat transmission twice as well as composition shingles.
Wood shingles often require more maintenance than other roofing options, especially if you live in a harsh climate. In such areas, it is advisable to treat wood shingles and shakes with a preservative every five years or so. Regular cleaning also is recommended to clear away debris that traps moisture and breeds fungus, mildew, rot and insect borers.
Wood shingles and shakes are not fire-resistant and some local codes may even require that the wood be pressure-treated. Some localities have banned wood roofing altogether; be sure to check your local codes before deciding to use wood shingles or shakes. In addition, check with your insurance company to see if your premiums will be affected.
 PROJECT BASICS
TOOLS & MATERIALS
 Fig. 1INSTRUCTIONS Choosing between shingles & shakes
Shingles are thinner than shakes and are sawn smooth on both sides. Shakes often are split by hand rather than cut and have a very irregular surface. They are thicker and therefore more durable than shingles, which typically last no more than 20 to 25 years. There are two common types of shakes used in residential roofing (Fig. 1). One type, called tapersplit, is split on both sides. Tapersplits are made by hand. The other type, called handsplit and resawn, is split from the block and then sawn to produce two shingles, each with one split and one sawn face.  Fig. 2Grade 1 is cut from heartwood, a clear (knot-free), completely edge-grained wood that is more resistant to rot than other grades. Grade 2 is flat-grained and has some knots as well as a limited amount of sapwood (sapwood is less rot-resistant than heartwood); grade 2 is acceptable for residential roofing. Use grade 3 shingles or shakes for outbuildings only. Grade 4 shingles have large knots, and are acceptable only for a starter course. Shakes aren't available in grade 4. The shingle length needed is determined by the desired exposure (the length of shingle exposed to weather). Exposure is determined by pitch. Shingle widths vary from 3 to 9 inches. Reroofing with shingles and shakes
With proper preparation, a roof can be covered with wood shingles. However, you cannot shingle over shakes due to their irregular shape. Both shingles and shakes can be installed over composition shingles. In order to install shingles and shakes, the roof must have a large enough slope. The reason for this is simple. Unlike self-sealing composition shingles or roll roofing, voids remain between courses of wood shingles and shakes. With enough pitch for quick runoff, this poses no problem, but when installed on a low slope, roof shingles are not protected from windblown rain and snow. Shingles are not recommended for roofs with less than a 3 in 12 pitch. Shakes are not recommended for roofs with a pitch of less than a 4 in 12. Exposure also must be limited for slight pitches. For example, with a 3 in 12 pitch, 16-inch shingles must have a maximum of 3-3/4-inch exposure (5 inches on 4 in 12 pitch). Eighteen-inch shingles may be exposed a maximum of 4-1/4 inches (5-1/2 inches on a 4 in 12 pitch). Shingles that are 24 inches long can have the greatest exposure (5-3/4 inches on a 3 in 12 pitch and 7-1/2 inches on a 4 in 12 pitch).  Apply shingles and shakes with only two nails per shingle. As the courses overlap, four nails pierce each shingle or shake. Place nails about 3/4 inch from each edge and 1 to 2 inches above the lowest edge of the overlapping course. Stagger joints at least 1-1/2 inches. (Fig. 3) Fig. 4To keep courses straight, tack a 1x4 guide in place for each course, or use the adjustable gauge on a roofing hammer. (Fig. 4)  Fig. 5Building special helpers
Wood shingles and shakes are slippery compared to the gritty grab of composition shingles, so it's a good idea to use a toeboard to help keep yourself and your materials on the roof. A toeboard is simply a long 2x4. Use three shakes or shingles as shown in Fig. 5 to shim the toeboard off the roof and give you a deeper toehold. Use 16d or 20d nails through the toeboard, shims, roofing and sheathing and into the rafter below. For a handy place to nest a bundle of shingles, nail two scrap shingles upright on the toeboards. Use a toeboard every 3 or 4 feet up the roof. A simple seat with a spiked base that grips the newly applied shingles also comes in handy. Build it with plywood and 1x4s. Drill 1/16-inch pilot holes and screw the pieces together with 6x1-5/8 galvanized deck screws. Drive roofing nails through the 1x4s before attaching them to the seat. The nails stick into the roof to keep you from sliding.  Fig. 6Applying sheathing and underlayment
Wood roofing benefits greatly from ventilation, so it almost always has spaced sheathing. The space allows shingles to dry after rain, thereby preventing rot. Solid sheathing, however, still is used at ridges, eaves, rakes, and places exposed to great amounts of wind and snow. Always use 30-pound felt underlayment when installing shakes. The irregular shape of the shakes allows plenty of air circulation. For wood shingles, use underlayment only in areas where ice may collect and at the eaves and rakes.
Before laying shakes (not shingles), nail a drip edge along the eaves. Begin by laying a full sheet of felt. All subsequent sheets are 18 inches wide. If you cannot purchase 18-inch felt, cut the sheets to size. When adding a layer of new shingles over old, ventilation channels are made by installing a new underlayment. This process includes removing old shingles, furring out the ridge, renewing the valley flashing, and adding a 1x6 nailer at the eaves and rakes. By adding a similar system of underlayment, wood shingles can be installed on top of composition shingles. Trim back the composition shingles where they extend beyond the edge of the roof before installing underlayment.  Fig. 7Fur out the valley to bring it to the level of the original shingles. Resurface with new flashing. (Fig. 7)  Fig. 8Beveled siding turned upside down reinforces the ridge and counteracts the bevel of the last course of shingles. (Fig. 8)  Fig. 9Use the sharp edge of a roofing hammer to cut away shingles along the rake and eaves. Open a cavity into which a 1x6 piece of sheathing can be nailed. (Fig. 9)  Fig. 10Covering composition shingles 1) Trim the old shingles Use a sharpened roofing hammer to cut away the overhang created by the old composition shingles. (Fig. 10)  Fig. 11Using 8d galvanized nails, add 1x6 sheathing to provide a solid nailing surface at the ridge, rakes and eaves. Use pairs of 1x3s in the valleys. (Fig. 11)  Fig. 12Space 1x3s a distance equal to the desired exposure of the shingles. Metal flashing is applied to the valley before installing shingle courses.
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