![]() Perfect Roof Rafters – Focus your efforts on the pattern rafter, and the rest of the roof falls into place easily.Steve is a Sound Designer & Lecturer whose work spans a number of creative fields including film, TV, theatre, live events, sound installation, advertising, music and education. Photos by: Tom O’Brien drawing by: Dan Thornton If you don’t have a helper, use a Quik-Grip clamp to hold the pattern rafter in place. Place the pattern over the top of each new piece of rafter stock, then mark the cuts. Framing lumber won’t be uniformly straight and true, so it’s good practice to orient rafters so that their crowns will face upward when they’re installed. Step 7: Keep crowns up when tracing the pattern. You’ll need the saw to cut into the corner from both sides. Step 6: Complete the bird’s mouth with a handsaw. Make sure that the blade is sharp and set square with the base of the circular saw. This rafter will serve as a pattern for all the others, so it’s important to make precise cuts. Step 5: Cut the first one with extra care. The first rafter is a pattern for the rest As the name implies, these little gadgets also are handy for laying out stair stringers. Clamped to the legs of a framing square at rise and run points, stair gauges act as stops to ensure that the rise and run settings remain consistent throughout the layout process. ![]() The most useful accessories for laying out rafters are a pair of tiny clamplike devices called stair gauges (General Tools 21 Each gauge is a small hexagonal nut with a slot through the middle and a thumbscrew for securing it to the square. Stair gauges lessen the chances for error Measure the difference on the body of the rafter, then mark the cutline. If the rafter is to be secured to a ridge board, half of the ridge board’s thickness must be removed from the top end of the rafter. Step 4: Trim the plumb cut to account for the ridge board. But a simple plumb-cut rafter tail is a snap to lay out in advance: Flip the square 180° (tongue pointing downward) and step off the desired measurement from the bird’s-mouth plumb line to the end of the rafter tail. Many framers prefer to leave the tails long, then snap a line and cut them in place. ![]() Step 3: Flip the square to mark the overhang. Measuring from the plumb cut, make the level seat cut equal to the thickness of the wall assembly. The right-angled notch that fits over the top of the wall is called a bird’s mouth. Step 2: Plumb and seat cuts complete the bird’s mouth. Now you can “step down” the rafter to complete the total run. Mark the first plumb line near the end of the rafter to locate the ridge cut. ![]() Clamp stair gauges to the framing square to align rise and run measurements with the rafter’s top edge. The simplest method is to “step off” the layout in 1-ft. Once you know the pitch and the total run, you can lay out the cuts of the rafter in a number of ways. For a gable roof, the run is measured from the centerline of the ridge board to the outside edge of the top of the wall. Run is the horizontal distance that the rafter covers. In the gable-roof example shown here, a rafter with 6-in-12 pitch rises 6 in. To lay out a common rafter, you need the pitch of the roof, expressed in units of rise per foot of run. Laying out hip, valley, and jack rafters takes experience and skill, but if you’re building a simple gable or shed roof, all you need is the common rafter, the basic building block of roof framing.
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