Bracing & Restraint

  • The following Technical Q&A has been updated from the version that appeared in the 2006 June/July issue of SBC.  
  • Lateral restraints are installed to reduce the buckling length of the web(s), but must be restrained laterally to prevent the webs to which they are attached from buckling together in the same direction.
  • BCSI-B3, Permanent Restraint/Bracing of Chords and Web Members, provides general industry recommendations and methods for restraining web members against buckling.

A few years ago, Lumber Specialties, a component manufacturer in Dyersville, IA, wanted a way to show proper bracing in a residential home. They asked Jason Gross, an intern in their design department at that time, to build an exact scale model of a roof truss system to accurately show diagonal bracing, lateral restraint, and T-bracing per BCSI.

  • The truss industry follows the requirements of the building code and ANSI/TPI 1 for general project scope of work concepts.
  • The Truss Designer identifies the location of required individual truss member lateral restraint and diagonal bracing on each Truss Design Drawing.
  • The JOBSITE PACKAGE can prove invaluable in documenting that the CM provided industry best practices on truss bracing, particularly when a project goes in a bad direction.
Understand the potential for future BCSI
optimization using SBCRI truss assembly test data.
  • CMs deal with customers with a wide range of skill sets, including those who have drawn their house plans on a McDonald’s paper napkin. I wish I were making this up!
  • While CMs are not responsible for ensuring that customers brace jobs correctly, they can provide BCSI documents to help customers build a better building and stay safe.
  • The BCSI book and B-Series Summary Sheets are a CM's saving grace, especially if the customer plans to install the trusses on their own or not hire an engineer of record.

In case you ever needed a picture to define the importance of diagonal bracing in the context of lateral restraint (i.e., top chord purlins as well), these photos of long span trusses say it all.