Continuous Lateral Bracing
How important is continuous lateral bracing in roof trusses? Is it detrimental to the roof integrity if it is missing?
Continuous lateral bracing (or restraint) is VERY important.
There are two separate types of bracing to be concerned about: permanent bracing listed on the truss design drawing for specific web members and permanent bracing for the roof or floor system. Certain truss members require bracing in order to carry the full design load. Without it, these members may buckle at loads far less than what they were designed to support. The truss design drawings will specify which members require this bracing and the approximate location that this bracing is to be applied. SBCA’s BCSI-B3 Summary Sheet provides guidance on this bracing as well as system bracing. It may be possible to brace the truss members with other types of bracing, such T bracing, L bracing or scabs. Contact your truss manufacturer for acceptable alternatives for any specific application.
The issue of permanent individual truss member bracing has been addressed in IBC since the 2009 edition (for example, see IBC 2012/2015 2303.4.1.2). It is the responsibility of the building designer to determine the size, type and method of attachment of this bracing to the trusses as well as how this bracing is to be tied into the rest of the building.