Pick-Points for Hoisting Trusses
Pick-Points for Hoisting Trusses
stress when hoisting trusses.
Hoisting trusses with a crane is a common practice on jobsites, but it’s also a likely time when trusses can be damaged. This is due to improper techniques that can overstress the truss and its connections. The following question from a truss designer deals with best practices for hoisting individual trusses and truss bundles.
Building Component Safety Information: Guide to Good Practice for Handling, Installing, Restraining & Bracing of Metal Plate Connected Wood Trusses (BSCI) states that trusses should never be lifted from the peak. I’ve seen documents from other companies that say no truss over 20' can be lifted at the peak. I know this will add lots of stress to that joint on larger trusses. What are your thoughts on this? Should this be handled any differently when hoisting bundles of trusses?
As you noted, lifting trusses from a single pick up point at the peak can add a great deal of stress to the peak joint. This applies to all trusses, regardless of size, but this stress and any resulting bending or damage can be especially pronounced in longer span trusses. Both the wood and cold-formed steel versions of Chapter B1 of BCSI and the B1 Summary Sheet discuss handling and hoisting of trusses. The following is based on the industry best practices in BCSI and CFSBCSI.
Hoisting Individual Trusses
Installers should not lift single trusses by the peak. Likewise, single trusses should not be lifted by the webs, which can cause lateral bending of the truss and damage to the truss plates and web member. Lifting devices should be attached to the truss top chord using only closed-loop attachments (see Figure 1).
Individual trusses up to 30' in length should have two pick-points near top chord joints spaced up to half the truss length apart. The line angle should be 60° or less. Spreader bars can help add rigidity to a truss while it’s being hoisted, lessening the likelihood of lateral bending. For trusses between 30' and 60', attach the truss to a spreader bar with lines that slope inward or “toe-in.” For trusses over 60', use a spreader bar two-thirds to three-quarters of the truss length positioned at or above mid-height of the truss. Attach the spreader bar to the top chords and webs at 10' intervals (see Figure 2 and Photo 1).
Hoisting Truss Bundles
The recommended industry best practices for hoisting truss bundles are a bit different than those for single trusses, but the same basic concepts apply (see Photos 2 & 3). When lifting truss bundles, lift points are permitted anywhere along the chords. “Anywhere” means anywhere other than the peak. Trusses that are banded together into a bundle are stiffer in comparison to a single truss, but lifting a bundle of trusses by the peak can still cause undue stress and damage.
For bundles of trusses greater than 45' and up to 60' in length, at least two lift points are required. For bundles of trusses greater than 60' in length, at least three lift points are required. Only one bundle should be lifted at a time. If a large bundle is comprised of smaller bundles, the large bundle should be taken apart and each bundle lifted individually.