How to Convert Roof Trusses

Written by mark morris | 13/05/2017
How to Convert Roof Trusses
Attic trusses must have minimal interior supports. (Wooden truss image by Burtsc from

Roof trusses are the quick, easy, and modern method for framing residential roofs. They are faster, stronger, and less expensive than traditional stick framing. One major drawback is the lack of customisation available in commercial prefab trusses. The webbing, or support bracing, severely limits the amount of usable space inside the attic. You can convert trusses to provide adequate support, while allowing enough space for a usable attic. It is best to convert the trusses prior to installation.

Lay a truss on saw horses face up. Set a circular saw depth equal to the thickness of the truss, including the gusset joint plates. Cut along the inside edges of the top diagonal and bottom horizontal pieces, known as the upper and lower cords, at each joint between the outside triangular frame and the interior braces. Cut through each brace at both ends and discard them.

Find the middle of the bottom horizontal board, or lower cord, and mark it. Measure from the outside end of the lower cord to the middle point. Divide this by two. Make a mark at a distance equal to the divided distance, or 1/4the width of the truss. Repeat this action on the opposite end of the truss.

Use a drywall square aligned with these two marks to mark the upper cord directly above the mark you made on the lower cord. Position a piece of 2-by-4 lumber with its bottom end centred on this mark and resting on the top edge of the lower cord. Align it so that the mark above, on the upper cord, is centred under it. Mark the 2-by-4 where it intersects with the upper cord. Make a second one for the opposite side of the truss.

Cut the 2-by-4 to length along a line between the intersection marks. Fit the 2-by-4 in place, with its angle-cut top butting against the bottom of the upper cord and the square-cut bottom end against the top of the bottom cord. Trace the outlines of these joints onto ½ inch plywood and cut two pieces for the top and two for the bottom of each 2-by-4 brace.

Fit the braces in place and apply construction adhesive to the backs of the plywood gussets. Staple the gussets in place, one at each end of each brace, on both faces of the truss.

Things you need

  • Circular saw
  • 2-by-4 lumber
  • Drywall square
  • Tape measure
  • 1/2 inch plywood
  • Construction adhesive
  • Staple gun

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