Roof Truss Layout Measurements

Improperly spaced trusses will not provide correct nailing points to secure decking.

Roof truss layout measurements. Standard truss boards are spaced 24 inches apart from one end of the roof to the other. Your top chords can protrude beyond the bottom chord anywhere from 1 3 feet 0 30 0 91 m. To obtain the actual height of the truss deduct the height of the wall from the total number calculated on the roof truss calculator see resources. The truss is a framework consisting of rafters posts and struts which supports your roof.

The second step in building a roof truss is to prepare the materials needed. For example a slope of 6 12 means for every 12 inches of horizontal distance the slope of the roof will rise 6 inches vertically. A 12 in 12 pitch is a steep 45 degree angle roof. See the image below for more explanation on rise run and pitch.

These measurements are for a common roof trusses. The run or the base number is 12 inches. The very first step for building roof trusses is to prepare a design layout that can be sketched by a professional architect or can also be done by using a software that is specifically meant to design a roof truss. On some roof trusses the 2 top chords extend down over the edges of the bottom chord creating a built in overhang.

These will include wood a hammer a saw roof truss. Use of manufactured roof trusses can dramatically cut labor costs when framing a gable roof compared to building rafters. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs. Pitch slope the pitch or slope is the incline of the roof expressed as a fraction describing the rise over the run.

If you think you d prefer an overhang style truss adjust the measurements for your top chords accordingly. This conforms to the 4 by 8 foot dimensions of plywood or oriented strand board osb sheets used to deck or cover the roof in preparation for shingles. Roof pitch is the rise over the run of the roof meaning a 7 12. There are other types of roof trusses that require different measurements.

Trusses can be constructed with smaller sized lumber than rafters and often their cost is not significantly higher than normal rafters.