Building a Garage - Roof Framing

Looking upward at a roof frame made of wood.
  • 4-50 hours
  • Advanced
  • 1,000-15,000

Ordering the Trusses

The difficulty of roof framing ranges from simply securing prefabricated roof trusses to cutting and assembling a complex roof design from scratch. This article will cover only the basic truss construction, as this is the recommended procedure for novice builders. Roof trusses are a pre-built series of structural members designed to carry the load of the roof to the outside walls. The structural members are most often 2x4s or 2x6s.

Trusses are ordered through your supply store and built in special factories to your individual specifications; however, home centers and building supply companies stock the standard sizes for most garages. Garage kits usually provide the necessary trusses, but if you've made some alterations to your roof line, you may need to special order them.

Important Information

Your garage plans should include the following information to aid you when ordering the roof trusses: slope, size of rafters, spacing, length of overhang, location and size of ceiling joists, size of ridge beam and any other bearing beams, and load weight.


Check with your supplier first to see if they have a special truck that can deliver and place the trusses on top of the walls. They may even have a crane truck that can gently lift the trusses and set them in place for you.

Usually the supplier can deliver everything needed for a roof frame in truss form. If, however, you have a more custom roof line, you may need to build all or part of the frame yourself. Building your own is well within the skill level of a novice, although we would advise consulting with local professionals and more detailed carpentry books for more information on rafters. If you plan to heat the garage and insulation is to be placed between the rafters, the space must be wide enough to provide for the thickness of the insulation. Rafters are placed at 12, 16, or 24-inch intervals. Check your local building code for the specific interval as it can vary by area*. The size, spacing, and span of the roof rafters must be coordinated to effectively carry a given load weight for your area. This load includes such factors as roofing materials and snow or ice accumulation.

roof layout
Roof Layout

Just as you measured for spacing of the wall studs, you will need to measure for, and mark the location of, the roof trusses on the cap plate. Check your local building code again for proper size and spacing.

Most Common Mistakes

Ordering inaccurate trusses.

Not accounting for overhang and rake rafters.

Neglecting to inspect the trusses upon arrival at the building site.

Placing the rafter on the wrong side of the layout mark.

Note: Rafters are doubled to support a rake rafter.


Beginning at one end, drive a nail 3/4 of an inch from the end, hook your measuring tape to the nail, then measure and mark every 24 inches (or 16 inches). Place an X on the side of the mark nearest your nail.

If, in your plans, you have an overhang (rake rafter) on either end of the garage, you will need to adjust the measurement to insure a sheet of plywood beginning at the edge of the overhang (rake) will end in the center of an interior truss.

Metal rafter ties make the installation of trusses easier and more secure.

Step 1 – Place the Rafter Truss

Very carefully lift one end of the rafter truss and carry it up the ladder. Rest it upside down next to the end set of metal rafter ties. Then, place the other end into position on the opposing wall.

Step 2 – Turn the Truss and Secure

Slowly and carefully turn the truss right side up and slide it into place. You may find it helpful to nail a 2x4 to the truss as a leverage board to swing the rafter upright and into place.

Nail the rafters tie in place over each X where the rafter will connect with the cap plate.

While one person holds a four to eight-foot level against each truss and holds it in position, another person will nail a temporary brace to the unit across the sloping top chord. Continue this procedure until all rafters are up and in place.

Most Common Mistakes

Placing the rafter on the wrong side of the layout mark.

Not plumbing the trusses.