Roof Truss Depth To Span Ratio

The lower the ratio the longer are the shear members in the truss and the larger is the volume occupied by the roof structure.

Roof truss depth to span ratio.

Roofs should have a minimum slope of in. The span to depth ratio of trusses ranges from 10 to 25 depending on the intensity of the applied load. Cantilever with concentrated load at the end of the cantilever is 2 times the depth of the truss. Floor trusses rules of thumb.

L d ratiothe ratio of the truss span l to its depth d both dimensions in inches. Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches. Maximum span to depth ratio of 20 max. Add 6 for roof trusses and 4 for floor trusses to your answer.

Estimate of depth 1 for every foot of span. 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. Cantilever without a concentrated load at the end is 4 times the depth of the truss max. The load span tables shown below demonstrate only a tiny subset of the possible combinations available with trussteel cfs roof trusses.

Live loadany temporary applied load to a floor truss chord. Per ft for proper drainage although steeper slopes are often desirable. Representative floor truss tables. Cantilever is of the total span max.

The architectural design of the building determines its external geometry and governs the slope s given to the top chord of the truss. 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. Typically roof live load is snow while floor live loads are furniture human occupancy storage. 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.