Haun_Larry_-_The_very_efficient_carpenter

Cuts on a Common Rafter

Level seat cut

Heel plumb cut

Plumb tail cut

Simple site-built rafter horses allow you to mark and cut all of the common rafters at once.

mouth cuts. The ridge cut is a plumb cut on the rafter stock that will fit against the ridge when the roof is built. The bird's mouth is the notch in the rafter that rests on the double top plate. It consists of a plumb heel cut and a level seat cut.

Rafters are generally cut using a standard 7Y4-in. circular saw. This saw isn't the first choice for pro­ duction roof cutters, who prefer to use more spe-

cialized tools (especially when cutting simple gable roofs), but it is the more affordable choice for most all-purpose carpenters. If you are using a standard saw, begin by loading the rafter stock on edge on the horses with their crowns up, just as they will be when installed. Leave both the top and bottom ends of the stock hanging over the horses about 1 ft. Make sure that the rafter stock is long enough to in­ clude the tail or eave section of the rafter.

The rafters should be flush on the ridge end. An easy way to flush up the rafters is to hold the face of a stud against the end of the rafters and pull them against it one at a time using your hammer claws. From the flush end measure down on the two out­ side rafters and mark the theoretical length of the rafters, subtracting half the ridge thickness if this has not been done. Snap a chalkline across the tops of the rafters to connect the marks. This marks the location of the plumb heel cut on the bird's mouth.

Next, place the rafter template on the first rafter, flush with the ridge end, and scribe the ridge-cut line. Slide this rafter over and mark the second one, and so on down the line, leaving all the rafters on edge. When all the ridge-cut lines have been marked, align the registration mark on the template with the chalkline on the rafters and begin marking the bird's-mouth cut lines.

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Holding an aligning board in place with your knees, pull the rafters flush using the hammer claws.

With the ends flush and the rafter lengths marked, scribe the ridge-cut line using the template.

Use the same template to mark the bird'smouth. Match the registration mark on the template with the chalkline on the top edge of the rafter.

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Laying Out Rafters

Align registration mark on the template with chalkline.

Tailsare cut after roof is stacked.

Rafters must be flush on the ridgeend.

Rafter horse

Ridge plumb-cut line

Once all the rafters have been marked, make all the ridgecuts.

Some buildings have barge rafters that form an overhang at the gable ends supported by lookouts (see pp. 155-156). A lookout is a 2x4 laid flat that butts against the first inboard rafter, passing through a notch cut in the end rafter and cantilevering out to support the barge. Lookouts are usually installed near the ridge, just above the plate line and 32 in. on center in between (closer for wide overhangs or heavy barge rafters). If the overhang is to be sheathed with 4x8 panels and left exposed, space the look­ outs every 48 in. on center from the bottom. This way they will hide the joints of the sheathing. Pick out four straight rafters, stack them together on edge and layout notches 3Yz in. wide.

When all the rafters have been marked, make all the ridge cuts with your circular saw, moving the rafters over one at a time. Then flip the rafters onto their sides and make the cuts for the bird's mouth, overcutting just enough to remove the wedge but not so much that you weaken the tail section. Cut the notches for the lookouts by first making two square crosscuts 1Yz in. deep, 3Yz in. apart, across the top edges of the four end rafters. Then turn the rafters on their sides and plunge-cut the bottom of the notch, removing just enough wood for a 2x4 to fit snug.

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If lookouts are needed to help carry the barge rafte" now is the time to mark and notch the end rafters.

Production layout and cutting

People who cut a lot of rafters, especially profession­ al roof cutters, use a variety of specialized tools that allow them to gang-cut common rafters, saving time in the process. These production methods require that the rafters be stacked on edge on the horses with the crowns facing down. Flush up one end and snap a chalkline about 3 in. down from the flush end (the greater the roof pitch and rafter width, the greater this distance needs to be). The chalkline marks the short point of the ridge plumb cut. Mea­ sure down from this line the theoretical rafter length and snap another chalkline, which marks the heel cut of the bird's mouth. Then, measure back up from this mark about 2)12 in. and snap a third line to mark the seat cut of the bird's mouth. This measurement will vary depending on the size of the rafters, the pitch of the roof and the cutting capacity of your saw (more on this later).

The rafters are now ready to be gang-cut. A 16-in. Makita beamsaw will cut through a 2x4 on edge at more than an 8-in-1 2 pitch (33%°) and will saw

A 1 6 -in. circular saw (top) or a worm-drive saw equipped with a beam-cutting attachment (above) canmake the ridgeplumb cut ona rack ofrafters in a single pass.

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A circular saw fitted with a swing-table accessory (left) can make the seat cut on a rack of rafters in a single pass. The more expensive dado rig(right) can gang-cut the entire bird's mouth in one quick pass.

most of the way through a 2x6 at a 4-in-12 pitch (18Yz°). To determine the angle at which to set your saw, check a rafter-table book.

For steeper pitches or wider stock, make a single pass down the chalkline with the beamsaw or stan­ dard circular saw, and then finish each cut with the circular saw, moving the rafters over one at a time. This way, the only mark needed is the chalkline.

The kerf from the first cut acts as a guide for the sec­ ond cut. Tomake this process go even faster, apply paraffin to the sawblade and table. Also, try to stay close to your power source. If you have to roll out 100 ft. of cord or more, the saw will lose some pow­ er and won't operate at its maximum efficiency.

Another method for gang-cutting ridges is to use a chain saw-type beam cutter such as the Linear Link model VCS-12 saw (Muskegon Power Tools, 2357 Whitehall Rd., Muskegon, Mich. 49445). The VCS12 is a worm-drive saw fitted with a bar and cutting chain that can cut to a depth of 12 in. at 90° and is adjustable to cut angles up to 45°. The saw leaves a good clean ridge cut and is easy to use, although it does require special care to use it safely. Read the in-

struction manual carefully. Also available is a beam­ cutter conversion kit for worm-drive saws (Prazi USA, 1 1 8 Long Pond Rd., #G, Plymouth, MA 02360).

With the right tools, the bird's mouths can also be gang-cut with the rafters on edge. For the heel cuts, set your circular saw to the same angle as the ridge cut and to the proper depth, and then make a single cut across all the rafters. Seat cuts are made using a circular saw fitted with a swing table (Big Foot Saws, Box 92244, Henderson, NV 89015). A swing table replaces the saw's standard table and allows the saw to be tilted to angles up to 75°. Just set the swing table to 90° minus the angle of the plumb cut and make the cut in one pass.

One problem with using a swing table is that it won't give you a deep cut at this sharp angle, so it limits the amount of bearing that the rafters will have on the top plates. This shallow cut is of little concern if the roof is framed properly. But for jobs requiring a deeper cut, Pairis Enterprises also makes a swing table to fit the 16 -in. Makita beamsaw.

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The few minutes it takes to nail down a catwalk under the ridgemakes installing rafters much easier and safer.

Laying Out the Ridge

Rafters should cover the joint between ridgesections.

ably from the catwalk, you need to set up staging on the ceiling joists. Lay down one or two rows of ply­ wood directly under the ridge. Then set two strong sawhorses on the plywood and run 2xlO or 2x12 planks between them. Experienced carpenters fac­ ing a high ridge often frame and brace the bare bones of the roof from the catwalk and then install the rest of the rafters while walking on the ridge. In a room with a cathedral ceiling, you will have to set up staging on the floor. Common sense dictates that any scaffold you use be safe (see the sidebar on the facing page).

Next, layout the ridge board. Most codes require that the ridge be one size larger than the rafters to ensure proper bearing (for example, 2x4 rafters need a 2x6 ridge). Most roofs will require more than one piece of ridge stock to span the length of the build­ ing. As you lay the ridge boards out, cut them at a layout mark so that each joint falls in the center of a rafter pair. The rafters will then help to hold the ridge together. Let the last ridge board run long-it will be cut to length after the roof is assembled. If the plans indicate that the ridge should run beyond the building line to help carry barge rafters, rip the overhanging piece to match the size of the rafters for a better appearance.

Be sure to align the layout of the ridge to that of the joists so that the rafters and joists will tie to­ gether at the plate line. If both are spaced 16 in. on center, every rafter will tie into a joist (see the draw­ ing on the facing page); if the joists are 16 in. on center and the rafters 24 in. on center, then a rafter

Ridge

Ridge ripped to width of common rafter in overhang

Rafter	End rafter

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