The report concludes that using advanced crane erect timber MMC systems reduces H&S hazard exposure by 20%.
Deep dive H&S risk profiling methodology and assessments were developed and undertaken on the following build techniques:
- GEN1 forklift & loose joists vs GEN3 crane & floor cassettes
- GEN1 forklift & site fitted windows vs GEN3 crane & pre-fitted windows
These assessed the safety requirements and risk profiles associated with the differing techniques and working practices to HSE risk exposure categories.
AIMCH focus is on building a weatherproof, insulated, and secure structural shell in one day, ideally with no scaffolding and a pre-tiled roof. This requires the use of a crane and the scaling up of panelised MMC solutions.
The work provided two key conclusions:
1. Advanced MMC can reduce risk exposure on-site by 20%, with a changed risk profile compared with more traditional methods
GEN3 crane erect advanced MMC systems can provide a generally safer on-site working environment, although the H&S risk profile differs from traditional systems. This is because many smaller, more frequent, and lower impact risks, which can over time lead to health issues like musculoskeletal disorders (MSD), are reduced or eliminated in GEN3. However, there is an increase in risk of very low likelihood but high-impact safety events due to the use of a crane for heavy lifting operations.
2. Some risks associated with advanced MMC methods are displaced to MMC factory
There is a transfer of some safety risks from the construction site to the factory environment. While this is beneficial to constructors, it is recognised that the MMC supply chain must drive safe factory operations to ensure that there is no net increase in risk for more advanced MMC-built homes. Risks can be more easily mitigated within the factory environment, where workplace safety systems are generally well managed. The procurers of MMC systems must ensure that effective controls are put in place to ensure net safety gain is realised, and risk is not merely abdicated.
The following approach was developed to undertake H&S risk profiling studies of MMC systems, trialled by AIMCH partners:
- Review MMC definitions & HSE safety classifications
- Identify MMC systems to be assessed
- Develop assessment methodology
- Carry out a subjective assessment of risk impact
- Final report
An early part of the work was to narrow down the risk profiling assessments, since it is evident that there are a wide range of safety changes when using MMC systems.
Crane-erect panelised MMC systems are favoured by AIMCH developer partners, providing a scalable outcome from the project. Within this approach, it was agreed to undertake deep dive desktop risk assessments of two areas of increased prefabrication that are likely to become commonplace.
Two deep dive case studies were developed:
GEN3 crane erect, MMC floor cassettes vs GEN1 forklift & loose joists
There is a fundamental safety improvement between the two methods. GEN 1 loose joists rely on manual labour and material movement on-site and the installation of a safety decking system. GEN3 floor cassettes significantly speed up the process and remove many of the risks associated with it. However, the installation of pre-manufactured cassettes brings with it new risks associated with the movement of large heavy loads.
GEN3 crane erect, factory-fitted windows vs GEN1 forklift & site fitted windows
In the eyes of the constructor the use of factory-fitted windows reduces associated H&S risks/hazards on the building site. This approach also changes the risk profile on the site by removing many lesser risks, but introduces a few high impact risks.
The shift in risk profile requires constructors to have early engagement with MMC suppliers/installers, to ensure the net safety benefits are retained through the pre-construction safety planning stages.
However, it is important to realise that some risk is displaced to the MMC supplier’s factory environment. It is therefore important to ensure that the net safety gain is fully achieved by ensuring the safety systems in the factory environment are managed more effectively than they can be on site.
Longer term, further hazards can be eliminated by MMC suppliers investing in automation and robotics to reduce the manual working and handling practises that are common within MMC factory facilities.