Standard OC Spacing for Roof Trusses

Effects of Spacing

• The spacing of trusses affects decking and shingling roof elements. Construction materials are sized in basic 2-foot elements, so improperly spaced trusses may not conform to 4-by-8-foot panels that are usually used for roof decking. Even metal roofing panels are generally sized for 2-foot spacing.

Standard Roof Spacing

• The typical spacing of roof trusses is 24 inches on center. That means the center of each 1 1/2-inch truss bottom chord, which spans the width of the roof, is 24 inches from the previous truss center. This spacing is used on all roof types with various pitches or slopes. Exceptions are found in areas with extremely heavy snow loads where building codes require 16-inch spacing.

Marking Trusses

• Marking the cap boards on the outside walls ensures proper spacing. The first end truss, typically at the rear of the house, is marked 1 1/2 inches in from the end of the wall with a line across the wall cap. The next truss location is marked 23 1/4 inches from the wall end. The third truss is marked 24 inches from that line. All other trusses are marked 24 inches apart with 1 1/2-inch spacing for the truss chord. Making the first distance short ensures the truss centers will conform to roof decking.

Identical Markings

• Both wall caps on a house have to be marked identically, so trusses will be spaced evenly. Marking 16-inch spacing is basically the same. While the second truss is marked 15 1/4 inches from the wall end, the other truss end lines are spaced 16 inches from that line.