How to Make Roof Trusses

A truss is a type of built-up structural member that can be used in place of a single girder or beam. Trusses are made from multiple straight members (generally made from wood or metal) arranged in triangles. This design allows a truss to span a very long distance without intermediate support; they are preferable to large, heavy girders because of their low cost and easy implementation. For large construction projects, the design and fabrication of roof trusses should be handled by licensed engineers. However, for smaller projects, you can make roof trusses yourself in accordance with your project's needs.

Steps

1. Design your roof truss. As with any structural member, a faulty design will undermine even the most professional of installations. Your roof truss will need to be able to handle the expected dead loads and live loads on your structure's roof. The truss will also need to be supported adequately at its ends.
   
   • The best material for building trusses on a small scale project is sawn lumber. Dimension lumber and engineered woods like plywood are not available in the sizes and lengths necessary to build a solid truss.
   • The roof truss will have a horizontal lower chord, and 2 angled upper chords that follow the roof line. These chords will be connected by "web" members, which will be oriented to form triangles. Your design should call for the same size lumber for each member.
2. Saw the truss members to size. After designing the truss, saw each member to its required length. You will likely need to use more than 1 length of lumber to make the lower chord, so plan on joining the 2 pieces at the midspan of the truss. You will have stronger joints if you angle each cut so that it fits flush against the other members.
3. Lay the truss members out on the ground. Once all the chord and web members are cut to size, arrange them flat on the ground in the shape of the truss. Make sure that all the connections fit snugly, sawing off additional length if necessary.
4. Secure the joints with metal gusset plates. Lay out toothed gusset plates (often called "nail plates") so that they cover each joint, making sure that the plates cover each member equally. Hammer each gusset plate into the wood until the teeth are fully driven in and the plate sits flush against the lumber. Turn the entire truss over and repeat this process on the other side.
   
   • As an alternative, you can make your own gusset plates out of plywood. Lay pieces of plywood over each joint, covering about a foot (30 cm) of each truss member's length. Glue the plywood to the joint, and then nail it to each member to fully secure it. Repeat this process on the reverse side of the truss.
5. Install the roof trusses. Once the trusses are constructed, lift them into place and set them onto the top plates of the exterior walls just as you would a beam or joist. Toe-nail them into the top plate to secure them, and then make sure they are braced laterally using blocking or long purlins.

Things You'll Need

• Pencil
• Paper
• Sawn lumber
• Tape measure
• Circular saw
• Hammer
• Gusset plates
• Nails

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