Roof Truss Layout Measurements

These measurements are for a common roof trusses.

Roof truss layout measurements.

The truss is a framework consisting of rafters posts and struts which supports your roof. 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. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs. Trusses can be constructed with smaller sized lumber than rafters and often their cost is not significantly higher than normal rafters.

See the image below for more explanation on rise run and pitch. The important point to keep in mind when you use your truss calculator is that every truss calculation is completely unique and is based on the size of your roof and its specific dimensions. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally. A 12 in 12 pitch is a steep 45 degree angle roof.

Improperly spaced trusses will not provide correct nailing points to secure decking. There are other types of roof trusses that require different measurements. Pitch slope the pitch or slope is the incline of the roof expressed as a fraction describing the rise over the run. Your top chords can protrude beyond the bottom chord anywhere from 1 3 feet 0 30 0 91 m.

Roof pitch is the rise over the run of the roof meaning a 7 12. Use of manufactured roof trusses can dramatically cut labor costs when framing a gable roof compared to building rafters. 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. The second step in building a roof truss is to prepare the materials needed.

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. On some roof trusses the 2 top chords extend down over the edges of the bottom chord creating a built in overhang. The rise will be the elevation change over the 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.

The run or the base number is 12 inches.