Load Bearing Roof Truss

Two horizontal beams that extend beyond the load they re bearing and are fixed at one end.

Load bearing roof truss.

Trusses must be designed for any special loading such as concentrated loads from hanging partitions or air conditioning units and snow loads caused by driftingnearparapetorslide offfromhigherroofs. Both sides of the equation should be equal in order to end up with a stable and secure roof structure. The truss is a framework consisting of rafters posts and struts which supports your roof. The formula for truss loads states that the number of truss members plus three must equal the twice the number of nodes.

Roof trusses support a roof s weight by transferring the weight load downward and outward to the building s bearing walls. The double cantilever truss adds height to the structure and contributes to a light and graceful appearance. If there is a truss over the wall the wall is probably not load bearing since the truss bears the load. It s often used in high rise buildings such as exposition buildings and grand stands.

To achieve maximum indicated spans trusses may require six or more panels. For example a gable end truss may be designed with support members that transmit the roof weight load outward to the side walls allowing the end wall directly below it to have breaks or openings in it that would otherwise be impossible. If there is a column that supports the truss found in the wall the wall still would not be load bearing because the column is taking the load. You will need an engineer involved in this since many contractors will tell you anything to get the job.

As we will see below there are several different types of designs and this will impact the angles and designs of the overall truss. Engineered roof truss systems may be designed to eliminate the need for load bearing walls or change where the bearing walls are located. I would think that any wall with a truss over it is not likely to be load bearing. In structure with truss design in the properties dialog box select roof floor bearing options and after you change to yes in is unique to truss in general section click on the drop down menu of bearing design options.

Truss roofs are typically designed to use some interior walls as mid span support to save on costs associated with making the truss larger stronger. 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.