Live Load On Roof Truss Formula

In order for a structure to be sound and secure the foundation roof and walls must be strong and wind resistant.

Live load on roof truss formula.

Trusses can be constructed with smaller sized lumber than rafters and often their cost is not significantly higher than normal rafters. Both sides of the equation should be equal in order to end up with a stable and secure roof. Live load dead load roof cover 1 2 plywood shuttering 1 5 psf roof framing 3 5 psf 1 2 drywall ceiling 2 0 psf insulation 2 0 psf d l 19 psf total load 35 psf external wall. When building a structure it is important to calculate wind load to ensure that the structure can withstand high winds especially if the building is located in an area known for inclement weather.

The same thing is true for the bridge of the truss. As a result the live load dead load and distribution of forces are different. Since it is possible to use the attic for storage the live load of the attic floor is set at 20 psf according to code. Considering that roof trusses are normally spaced at 24 inches on center here are the load calculations.

Finally the truss calculator will compute the best dimensional method to connect the pieces of the truss with steel joints and a bridge. 2attic loads may be included in the floor live load but a 10 psf attic load is typically used only to size ceiling joists adequately for access purposes. The truss top chords bottom chords and webs are of 2x4 that weighs about 1 2 lbs ft. Use of manufactured roof trusses can dramatically cut labor costs when framing a gable roof compared to building rafters.

The formula for truss loads states that the number of truss members plus three must equal the twice the number of nodes. If the number of members is labeled m and the number of nodes is labeled n this can be written as m 3 2 n. These steel joints are needed to support the overall truss. Unlike the trussed roof live load and dead load of the rafters and ceiling joists must be accounted for as separate systems.

Adding up all the truss members comes out to a total length of 47 5 ft truss weight 1 2x47 5 57 pounds.