Two truss collapses in Minnesota this year, one fatal: how to brace trusses while you set them

The fatality log, updated Oct. 15, ties the Lakeville death to a framing contractor and a single-family home builder, each with six employees. The serious-injury log puts the Long Lake case under a framing contractor and a commercial builder. Minnesota OSHA has not released findings in either case, so the cause is not established. Occupational Health & Safety reported the updated logs on Oct. 30.

Bracing rules for trusses are set out in BCSI, the guide published by the Structural Building Components Association (SBCA) and the Truss Plate Institute. Its B2 summary sheet names skipped handling and bracing steps as the main cause of accidents during truss erection. The first truss, or the gable end frame, goes up plumb and is fastened to ground braces and the wall before the crane releases it. Top chord temporary lateral restraint goes no more than 10 feet apart for spans up to 30 feet, 8 feet up to 45 feet, 6 feet up to 60 feet and 4 feet up to 80 feet, with extra rows at pitch breaks.

Lateral restraint without diagonal bracing does not hold, the sheet warns. Once trusses two through five are set, the crew adds top chord diagonals or sheathing, web diagonals and bottom chord restraint no more than 15 feet apart, and only then takes down the ground bracing. After that, under the short-restraint method, no more than four trusses go up before the crew stops and braces again. Diagonals go at each end of a run and at least every 10 truss spaces, or 20 feet. Bracing stock is stress-graded 2x4s or approved metal restraint products, with at least two nails at each connection.

Sheathe early, the guide says, and pull only as much temporary restraint as the next sheet needs. For trusses spanning 60 feet or more, it calls for a registered design professional to draw up the temporary bracing plan and supervise erection.