Temporary Roof Edge Protection Over a Live Loading Bay
A two-storey distribution warehouse is having its roof replaced. The principal contractor wants a 1.2 m high guardrail erected along the full 60 m roof edge above a loading bay that must stay operational for deliveries between 06:00 and 14:00. The scaffold contractor proposes a tube-and-fitting edge protection system founded on the bay's concrete apron, with standards at 2.0 m centres and ties into the roof structure at 4.0 m horizontal and 4.0 m vertical spacing. The apron has a 1:40 cross-fall toward a drainage channel, and the bay canopy projects 1.5 m beyond the building line below the roof edge. Deliveries include articulated vehicles reversing to within 3 m of the proposed standards. The client asks whether the protection can be classed as 'scaffolding' under the site's permit regime and whether the tie pattern is acceptable.
1. Assess the proposed tie pattern and foundation arrangement against the structural needs of edge protection that will be struck by wind and vehicle-induced vibration. What changes would you require before work starts?
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Tie pattern: A 4.0 m × 4.0 m tie grid is far too sparse for a free-standing edge-protection scaffold on a 60 m run. Wind loading on a 1.2 m high, 60 m long face is significant, and the structure has no diaphragm other than the tubes and fittings. I would require ties at no more than 2.0 m horizontal and 2.0 m vertical (i.e. at every standard and every lift) in the vicinity of the exposed corner and at least every 2.0 m along the run, with the pattern designed by a competent person and recorded on a drawing.
Foundations: The 1:40 cross-fall means base plates will not sit flat. I would require either (a) a designed sole-plate/base arrangement that accommodates the fall, or (b) a leveling grillage. The drainage channel must not be used as a bearing surface. Base plates must be on firm, drained ground with no ponding.
Vehicle impact: With articulated vehicles reversing to 3 m, I would require a physical impact barrier (e.g. concrete blocks or a designed vehicle restraint system) set out from the standards, plus a banksman and a revised traffic management plan. The 1.5 m canopy projection means the scaffold standards cannot be founded directly under the roof edge, so the design must account for the eccentricity of the roof-edge loads relative to the standards. This is a design change, not a site adjustment.
2. The client asks whether the edge protection falls under the site's scaffolding permit regime. Advise them, and state what documentation you would insist on before handover.
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Classification: The permit regime should apply. The structure is a temporary works structure erected from tubes and fittings to provide edge protection; it carries wind load and must be designed, erected, inspected and handed over like any scaffold. Classifying it as 'just edge protection' is the classic route to an un-designed, un-inspected structure. I would insist it is registered under the scaffolding permit, with a named design check and a named erection supervisor.
Documentation before handover:
- Design drawing and design check certificate from a competent person, including tie pattern, foundation detail and vehicle-impact provision.
- Risk assessment and method statement covering erection over the live bay, working at height, and materials handling.
- Evidence of competence of erectors (e.g. CISRS or equivalent) and supervisor.
- Inspection record at handover, signed by a competent person, with the tag fitted at the access point.
- A schedule of inspections (at least every 7 days and after any event) and a named person responsible.
- Confirmation that the loading bay traffic management plan has been amended and briefed to drivers.