As IOSH Magazine previously reported, the carpenter worked for Mitchellson Formwork and Civil Engineering, which was subcontracted by St James (part of Berkeley Group), which was principal contractor on the project. The companies were building two nine-storey mixed residential and retail units in Putney, south-west London.
Mitchellson's workers were responsible for building the temporary platforms for the site that were fitted above stairwell and lift-shaft openings, and for constructing formwork for the in-situ cast concrete. They also worked with steel fixers, whose job it was to reinforce the concrete.
On the day of the accident, it is thought that the carpenter and a steel fixer were both standing on one of the 2.45 m x 4.1 m temporary wooden platforms on the ninth floor. It gave way beneath them and they fell five storeys (16 m) on to a concrete staircase that had been part-built to level four.
The carpenter died at the scene and the steel fixer sustained severe injuries that left him unable to work for three years. He has since returned to the construction industry but cannot work at height. An engineer's assistant, who was in the stairwell on a lower level when the accident happened on 29 October 2012, was also seriously injured when he was struck by falling debris.
The Health and Safety Executive (HSE) visited the site and found that the temporary platforms were made of timber joists held up by joist hangers with plywood fixed on top. "Joist hangers are not designed to be used in that application," said HSE inspector Karen Morris. "They are not intended to be used as part of a working platform in this way."
She said that the joist hanger's flange was not fixed or weighted down, in accordance with the manufacturers' instructions. As a result, the steel flange bent upwards under the men's weight and this caused the platform to collapse and fall through the opening.
Morris drew attention to a 2006 alert on the installation of timber joist hangers, published by the Standing Committee of Structural Safety, which highlights that the HSE "reports that a number of collapses have occurred as a consequence of incorrect installation". It identified "building the joist hanger flange into the wall with inadequate masonry restraint above the masonry flange" as one cause of joist hanger failures.
The HSE's investigation also found the platforms had not been built to an agreed safe design. "There were no plans, diagrams, drawings or designs to work from," Morris said. "The key thing is that [the platforms are] designed properly by a temporary works designer, that someone checks the calculations, and that someone then checks that the platforms are built according to the design. There is no point having a design if no one follows it. In this case there was no design anyway."
More than one platform, similar to that which had collapsed, had been fitted on every floor of both structures on the construction site. Mitchellson took all of them out of service immediately after the accident and assured the HSE it would not use that system again.
St James has reviewed the way it manages temporary works. It has revised some of its procedures, given staff more temporary works training, and will appoint an external independent temporary works coordinator for all projects in the future.
St James and Mitchellson were sentenced at Southwark Crown Court. St James pleaded guilty to breaching reg 22(1)(a) of the Construction (Design and Management) (CDM) Regulations 2007 after it failed to safely plan, manage and monitor the work. It was fined £600,000 and ordered to pay costs of £14,935. Mitchellson was fined £400,000 plus £14,935 in costs after it admitted breaching reg 13(2) of the same regulations -- also for failing to safely plan, manage and monitor the work carried out under its control.
According to Morris, the judge said both companies had "systems in place to manage temporary works but they were not sufficiently adhered to" and thus categorised their culpability as "medium". The offence fell into harm category 1 as it resulted in death, and the likelihood was "high". Under the sentencing guidelines, St James was classed as a "large" organisation (£350m turnover) and Mitchellson was "medium" (£31m turnover).
She said the judge recognised their "dignified acceptance of responsibility", as well as their good health and safety records, full co-operation with the HSE and early guilty pleas.
RGF Construction, a "micro" organisation subcontracted by Mitchellson to provide a site manager to oversee its work, had already pleaded not guilty at an earlier hearing on 4 July. It was found guilty of breaching regs 13(2) and 28(2) of the CDM Regulations 2007, the latter of which covers the installation of temporary supports and structures. The company was fined £20,000 as it ceased trading two years ago and is about to be wound up.
