Roof Truss Depth To Span Ratio

Typically roof live load is snow while floor live loads are furniture human occupancy storage.

Roof truss depth to span ratio.

L d ratiothe ratio of the truss span l to its depth d both dimensions in inches. The lower the ratio the longer are the shear members in the truss and the larger is the volume occupied by the roof structure. Most economical when the difference in slope between the top and bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch. Live loadany temporary applied load to a floor truss chord.

Maximum span to depth ratio of 20 max. Cantilever is of the total span max. This will get you a starting depth for a basic truss. Cantilever with concentrated load at the end of the cantilever is 2 times the depth of the truss.

The architectural design of the building determines its external geometry and governs the slope s given to the top chord of the truss. Cantilever without a concentrated load at the end is 4 times the depth of the truss max. Estimate of depth 1 for every foot of span. Per ft for proper drainage although steeper slopes are often desirable.

05425 cold formed steel trusses roof truss spans every trussteel roof truss is a custom design based upon the unique load span bearing use and code criteria of a particular project. Representative floor truss tables. For flat trusses a minimum depth to span ratio between 1 8 and 1 10 is recommended the deeper trusses being preferred for the longer spans. For efficient structural performance the ratio of span to truss depth should be chosen in the range 10 to 15.

The span to depth ratio of trusses ranges from 10 to 25 depending on the intensity of the applied load. You will be able to decrease the depth if the truss company has higher grade lumber for the roof and floor trusses or uses double chords for the floor trusses. Roofs should have a minimum slope of in. The load span tables shown below demonstrate only a tiny subset of the possible combinations available with trussteel cfs roof trusses.