Fall Protection During Truss Setting on a Wet Roof
On a two-storey addition, the framing crew is sheathing a 7/12 gable roof. The eave is 6.7 m above grade, and only the lower half of the roof sheathing is installed. The site supervisor wants two carpenters to walk the top plates and set trusses before the scaffold is relocated. The only fall-arrest anchor is a manufactured roof anchor fastened with four 16d nails through the sheathing into a single truss bottom chord; no manufacturer’s instructions or inspection record are on site. Wind is gusting to 40 km/h and light rain is starting. One worker says he has used the anchor before and it “held fine.” The general contractor is pressing for the truss package to be set today because the crane is booked for tomorrow. The crew has harnesses, lanyards and a ladder, but no rescue plan or trained rescuer on site.
1. What should the crew do before any truss is moved, and how should the supervisor communicate the decision?
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The crew should stop work at the roof edge and not move any truss until the access and fall-protection plan is rebuilt. The immediate trigger is not just the wet, windy weather: the only anchor is unverified, there is no rescue plan, and workers would be walking top plates with incomplete sheathing. The supervisor should exercise stop-work authority, explain the specific hazards to the whole crew, and separate the schedule pressure from the safety decision. The crane booking does not justify using an unverified anchor. A useful communication is: no truss setting today until a competent person confirms a compliant work platform or fall-arrest system, including anchor installation, clearance, and rescue. The crew should be moved to ground-level pre-assembly or another task that does not expose them to an uncontrolled fall.
2. Evaluate the proposed fall-arrest anchor and the available ladder access. What would make either acceptable for this task?
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The existing anchor is not acceptable. Four 16d nails through roof sheathing into one truss bottom chord do not match the fastener, substrate, and installation requirements of a manufactured anchor, and there is no inspection record. A single bottom chord is not a verified structural anchor, and sheathing does not reliably transfer a fall load. An acceptable anchor would be specified by the manufacturer for the substrate, installed with the specified fasteners and orientation, inspected by a competent person, and used with a lanyard and harness that keep fall clearance and swing-fall hazards within limits. A ladder is access, not a work platform. For sustained work at the eave and roof, guardrails, a scaffold work platform, or an aerial lift would be preferable under the hierarchy of controls; fall arrest is the last line of defence and still requires a rescue plan.
3. Outline a safe sequence for setting the trusses tomorrow, including what must be verified and documented.
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A reasonable sequence is: pre-assemble and brace as much as possible on the ground; establish a stable work platform or verify a complete fall-arrest system with trained users and a rescue plan; confirm the crane lift plan and exclusion zone; set and brace the first trusses from a protected position; then install sheathing and temporary bracing before workers move along the roof. Before work starts, a competent person should inspect the anchor system, harnesses, lanyards, scaffold or lift, and weather conditions. The supervisor should document the hazard assessment, anchor installation and inspection, worker training, rescue arrangements, and any change to the planned work. If wind or rain makes the roof surface slippery or affects crane control, the lift should be postponed. Production should follow the controls, not the crane booking.