How to Make Compound Cuts on Roof Trusses

Some roof trusses require you to line the chords and webbing up at different angles. For example, if you have a pyramid-shaped roof, creating standard gable trusses isn't going to do the trick. You must make a cut that creates two angles at once rather than a single-angle cut. A cut along more than one angle is called a compound cut, and is done with a compound miter saw.

Compound miter saw
Truss blueprints
2-by-4 lumber
Tape measure
Ruler
Safety glasses
Hearing protection
Scientific calculator

Instructions

- 1
  Consult your truss blueprints and select the piece you want to cut. For example, cut one of the top chords. The roof will have a 6:12 pitch, meaning that it rises 6 inches for 12 inches of run.
- 2
  Input "6/12" in your calculator, then press "tan-1." This will give you the angle of the slope as 26.56 degrees.
- 3
  Connect your miter saw and put on safety glasses and hearing protection if necessary.
- 4
  Place the board's longest edge against the fence of the miter saw. The fence is a horizontal portion of the saw that provides a bracing point. Screw the clamps tightly to hold the wood in place.
- 5
  Set the miter angle of the saw according to the measurement in Step 2. Use the miter gauge. Some miter saws will have a laser line that indicates where the blade will make contact.
- 6
  Determine the angle you want to bevel the wood — 10 degrees, for example. Turn the saw blade on the vertical pivot until it matches 10 degrees.
- 7
  Lock the blade in place, press the trigger and pull the saw onto the wood to make the cut.

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