How to Cut Rafters for a Shed Roof

Although manufacturers can make trusses to match almost any conventional roof, cutting your own rafters may be the simplest, most cost-effective way to frame a shed roof. Once a few phrases and processes are understood, roof framing is a relatively simple process. Don't cut until you know the length of what's called the common, or template, rafter, which is based on the pitch, span and run of the planned roof. Then learn the meaning of plumb cut, ridge board, common rafter, birdsmouth cut and tail cut, which are all important when preparing to cut rafters for a shed roof.

Framing square
Circular saw
Wood pencil
Tape measure
Lumber

Instructions

- 1
  Familiarize yourself with roofing terms. The ridge board stretches from the front to the back of the shed and is the board that the rafters will connect to at the peak of the roof. A plumb cut is the cut you make in the rafter to line it up with the ridge board. The common rafter is the first one you cut, to use as a template for the others once you're sure of the angles and length. The birdsmouth cut is the notch made in the rafter to allow it to fit over the wall stud, and the tail cut is the one that determines the length of the eave overhang.
- 2
  Take your first rafter--the common rafter--in hand after you have figured the pitch, span and length. Mark the top plumb cut using a framing square. You will need to line the square up according to the pitch and run you've figured (which will depend on the size of shed you're building).
- 3
  Make the plumb cut with your saw, and check the cut by fitting it against the ridge board.
- 4
  Measure the rafter length and mark the outside edge of the building. Use this mark and a framing square to mark and cut the birdsmouth cut. This notch should be at least 4 inches long to allow the rafter to fully bear on the side walls.
- 5
  Mark the tail cut of the rafter using the framing square after you decide how long you want the eave to be. The bottom side of the tail cut should be at the same angle as the birdsmouth cut and on the same side, just several inches down the rafter. The top part of the cut should complement the angle of the plumb cut. The bottom of the rafter can also be cut in a simple 90-degree angle if you're not worried about making the bottom of the rafters look stylishly finished.
- 6
  Use the common rafter to cut a set of matching rafters, then test them against both sides of the ridge board to make sure the angles and cuts are correct. Do another set of rafters, checking the angles and cuts. If you're confident that they are satisfactory, you can use the common rafter as the pattern for the rest of the rafters--do not switch to a second rafter as a pattern.

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