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Worker injured by falling construction load

Date of incident: September 2015
Notice of incident number: 2015165870136
Employer: Modular home manufacturer

Incident summary
Workers were assembling modular houses, including assembling open web wood trusses in groups on the ground and then lifting the truss groups onto the modular house using a mobile crane. Three separate pairs of non-engineered wood brackets were mounted to the trusses, near the roof ridge, to support sheets of oriented strand board (OSB). Then the trusses were erected onto the modular house.


A worker planned to adjust some trusses that were not sitting level on a modular house. The worker accessed the roof and attempted to remove a piece of lumber adjacent to two brackets that had been loaded with sheets of OSB. The trusses collapsed. As the trusses collapsed, the sheets of OSB fell and struck the worker in the back. The worker was buried under the OSB and sustained serious injuries.

Investigation conclusions

Cause

  • Inadequate bracing. The trusses collapsed because the structural integrity and stability of the trusses were compromised due to inadequate bracing. The truss collapse caused sheets of OSB to fall and strike the worker in the back, causing serious injuries.

Contributing factors

  • Failure to follow manufacturer’s instructions. The employer failed to follow the manufacturer’s instructions regarding erection of the trusses by: 1) placing construction loads (sheets of OSB) near the peak and 2) inadequately bracing the trusses. The placement of three construction loads near the peak of the inadequately braced trusses negatively affected the structural integrity of the trusses. As a result, the structural integrity and stability of the trusses were not sufficient to prevent the trusses from collapsing.
  • Inadequate supervision. The supervisor failed to ensure he was knowledgeable about the regulations that were applicable to the erection of trusses, specifically the requirement to follow the manufacturer’s instructions. The supervisor did not ensure that workers were made aware of the foreseeable overhead hazard, nor did he ensure the health and safety of workers who were under his direct supervision.
  • Inadequate training. Neither the supervisor nor the workers received adequate training in relation to the erection of trusses onto modular houses.
  • Creation of overhead hazard. The sheets of OSB that were placed on brackets overtop of where workers were required to work created an undue overhead hazard.

Request the full report

Publication Date: Mar 2019 Asset type: Incident Investigation Report Summary NI number: 2015165870136