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. The worker was pinned 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, 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. Supervisors’ duties include ensuring the health and safety of workers under their direct supervision, being knowledgeable about regulatory requirements applicable to work they supervise, and making workers aware of all known or reasonably foreseeable hazards in the area where they work. The employer failed to provide its workers with the supervision necessary to ensure their health and safety.
- 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.