Untied Frame Scaffold in Rising Wind
A three-person crew is erecting a 28 ft high modular frame scaffold along a building facade. The scaffold is 5 ft wide and stands 3 ft from the wall. Base plates sit on 2x10 mud sills on frozen ground. The frame has no ties to the building; the crew says the 5 ft width gives a 5.6:1 height-to-base ratio and that frame scaffolds do not need ties until 30 ft. Outside guardrails consist of a 42 in. toprail and a midrail, but the ends and the wall side are open. Two 10 ft 2x10 planks are overlapped 6 in. and not cleated; workers stand on them at the 28 ft level. The only access is by climbing the end frames. Wind is steady at 22 mph with gusts to 30 mph. A laborer asks whether they can finish installing the last two frames and then tie off at the top. The competent person is off site.
1. Determine whether the scaffold is stable as built, including whether ties are required.
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The scaffold is not stable as built. The height-to-base ratio is 28 ft divided by 5 ft, or 5.6:1. Supported scaffolds must be restrained from tipping by guying, tying, bracing, or equivalent means. A common rule is that a scaffold more than three times its minimum base dimension in height must be tied; here three times 5 ft is 15 ft, and the scaffold is 28 ft. It therefore needs ties, and it has none.
The frozen ground and mud sills are also a concern because frost heave can change bearing and level. The wind is steady at 22 mph with gusts to 30 mph, which increases overturning forces on an unbraced, untied scaffold. The competent person must evaluate the scaffold before any further use. Do not finish the top frames first and tie later; the scaffold must be stabilized before workers load it.
2. Identify the fall protection, guardrail, plank, and access deficiencies.
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Deficiencies include:
- Guardrails: open ends and the wall side are unguarded. Guardrails are required on all open sides, including the ends, with a toprail, midrail, and toe board. A 42 in. toprail is within the usual 38 in. to 45 in. range, but the missing sections defeat the system.
- Planks: two 10 ft planks overlapped only 6 in. and not cleated can slip. Planks must be scaffold grade, secured from movement, and extend over supports as required. The platform should be fully decked for the work.
- Access: climbing the end frames is not an acceptable means of access. Provide a ladder or stair tower, secured and extending above the platform, with a safe landing.
- Fall protection: workers at 28 ft need guardrails or personal fall arrest with an anchor and clearance plan. The current open sides expose them to a fall to the ground.
- Falling objects: toe boards and screening may be needed to protect workers below.
3. What immediate action should be taken, and what must be documented before the scaffold is used?
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Immediate action: remove all workers from the scaffold, barricade the base, and tag it as not approved for use. Do not let the crew finish the top frames until the scaffold is tied or otherwise stabilized per the manufacturer's or engineer's instructions. If wind exceeds the manufacturer's limit, stop erection entirely.
Before reuse, the competent person must:
- Verify the base is level and stable, with proper mud sills and no frost damage.
- Confirm ties are installed at the required intervals and connected to a structure that can resist the loads.
- Check guardrails, planks, access, and fall protection.
- Document the inspection and the corrections made.
If the scaffold cannot be tied as required, it must be dismantled or redesigned. The crew's plan to tie off only at the top is not acceptable because the scaffold is already at risk of tipping.