Inspection Findings and Load Limits on a Working Scaffold
During a weekly inspection of a 12 m scaffold, the inspector finds: three missing guardrails on the third lift; a toe board displaced on the second lift; two standards bearing on soft ground with no sole pads visible; and a stockpile of 40 concrete blocks (each about 18 kg) plus two bundles of bricks on the fourth lift. The scaffold design allows a uniformly distributed load of 2.0 kN/m2 and a concentrated load of 1.5 kN. The lift is 2.0 m wide and 12 m long. The site manager says the blocks are 'only there for an hour' and asks the inspector to sign off with the defects noted.
1. Assess the load on the fourth lift against the design limits and state whether it is acceptable.
Read the worked answer
The stockpile must be checked against both the distributed and concentrated limits.
Distributed load. Forty blocks at about 18 kg is roughly 720 kg, or about 7.1 kN. Two brick bundles are not quantified, but even the blocks alone spread over a 2.0 m by 12 m lift (24 m2) give about 0.30 kN/m2, which is within the 2.0 kN/m2 allowance. However, the blocks are almost certainly not spread evenly; if they are stacked in one area of, say, 2 m by 2 m, the local intensity is about 1.8 kN/m2, close to the limit before the bricks are counted.
Concentrated load. A stack of blocks on a pallet or bearer can exceed the 1.5 kN concentrated limit locally. Forty blocks is about 7.1 kN, well above 1.5 kN if borne on a small footprint.
Conclusion. The load cannot be accepted as presented. The inspector needs the actual weight and footprint of the bricks, and the stockpile should be spread or reduced to stay within both limits. 'Only there for an hour' does not change the load the scaffold is carrying now.
The inspector should require the material to be redistributed or removed before sign-off, and should record the calculated figures.
2. List the defects found and explain the correct inspection decision, including what the inspector should do about the sign-off request.
Read the worked answer
Defects:
- Three missing guardrails on the third lift - a fall-protection failure at height. This is a serious defect and the lift should be taken out of use until guardrails are replaced.
- Displaced toe board on the second lift - a dropped-object risk to people below. It must be refixed before the lift is used.
- Two standards on soft ground with no sole pads - a foundation failure that can cause settlement, loss of level, and progressive instability. The standards must be founded on adequate sole pads or base plates on firm ground, and the scaffold rechecked for plumb.
- Overload risk on the fourth lift - as assessed, the stockpile must be redistributed or removed.
Inspection decision: the scaffold should not be signed off as fit for use. The inspector should record the defects, specify the actions and the lifts affected, and require re-inspection after correction. Signing off 'with defects noted' would misrepresent the scaffold's condition and could expose the inspector and others to liability.
The inspector's duty is to report honestly and not to be pressured by the 'only an hour' argument. The correct answer is a refusal to sign off until the defects are corrected and the load is brought within design limits.