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Study shows prefabrication reduces site hazards by 20%

14 Apr 22 A study of two timber frame building systems has shown, perhaps unsurprisingly, that the less activity done on site, the lower the risk of an accident on site.

Crane-based GEN 3 systems transfer some of the health and safety risks from the construction site to the factory

The study, commissioned by Stewart Milne Group for the Advanced Industrialised Methods for the Construction of Homes (AIMCH) research project, found that crane-lift panelised building methods provide 20% less exposure to health and safety risks on site than open panel timber frame construction using a forklift.

The £6.5m AIMCH research project, backed by Barratt and L&Q,  seeks to industrialise housing production by making panelised methods mainstream. Previous AIMCH research has demonstrated how panelised systems result in homes being built faster, more cost effectively, to a high quality and with a lower carbon footprint. This latest study finds they are also safer (for site workers, at least).

Panelised systems are increasingly used to build houses that have progressively more manufactured components such as prefabricated floor cassettes, ready fitted windows, and pre-insulated closed walls. These systems require a crane to offload and position the components on site.

The study, Health and Safety Risk Profiling of MMC Solutions, prepared by Stewart Milne Group, with support from Limberger Associates, assessed the difference in risk exposure between two timber frame systems: one built on site using manual assembly techniques with the aid of a forklift (GEN1), also typical of masonry-built homes; the other a more advanced system (GEN3), using higher levels of prefabrication, requiring the use of a crane on site.

Stewart Dalgarno, AIMCH project director and director of innovation & sustainability at Stewart Milne Group, said: “This is the first study we have undertaken to compare the health and safety risk exposure of both construction methods and it is gratifying to see that the crane-erect panelised MMC methods championed by AIMCH reduce safety risks and hazard exposure by 20% on site, where the injury rate per 100,000 workers is 42% higher than in manufacturing, and where 50% of deaths are attributed to falls from height, compared with 16% in manufacturing.”

Site assembly involves manual handling, which carries injury risks

The study evaluated working practices and techniques in two areas, floors, and windows, where increasing the pre-manufactured value (PMV) is getting more common. The study developed a methodology for assessing risk, aligned with Health & Safety Executive (HSE) hazard classifications, and consequential risk profiles were developed for each. These covered hazards such as falls from height; slips and trips; moving and handling loads; and lifting operations and were used to compare the effect of on-site working practice differences between GEN1 site assembly and GEN3 prefabricated construction methods.

The study of floors compared loose joists and forklift (GEN1) against prefabricated floor cassettes and crane (GEN3). Loose joists rely on more manual labour and material movement on site and the installation of a safety decking system, whereas floor cassettes dispense with the need for safety decking and speed up the installation process, removing many of the health and safety exposure risks such as trips and falls, manual handling, material movement associated with loose joist and flooring installation.

The report concludes 20% less H&S hazard exposure using advanced crane erect timber systems

Comparing site-fitted windows (using a forklift) against factory-fitted windows lifted in with a crane, the latter was found to reduce health and safety hazard exposure due to reduced manual handling.

In both areas the use of GEN3 systems transfers some of the health and safety risks from the construction site to the factory, “where workplace safety systems are generally better managed,” it is asserted.

However, with GEN3 systems, if something does go wrong, it is more likely to go wrong in a big way – floor cassettes might break their slings and slip off the end of the bearing when being placed. So despite safety risks being lower, strict safety protocols must still be in place.

To ensure that the transfer of risk from the construction site to the factory does not lead to an abdication of risk management, the report emphasis the important of suppliers investing in machinery and tools that reduce manual handling and injury risks.

The full report can be downloaded from www.aimch.co.uk

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