Turn up at a construction site using offsite manufacturing, and it can sometimes look like everyone’s on their lunch break. It’s clearly a very different place to conventional sites. Firstly there are just far fewer people – maybe just 30-40, for example, rather than 100 on a project to build a new school. It’s also quieter, cleaner and safer.
This new atmosphere isn’t the only thing that’s changed. Using offsite methods creates fresh site challenges that require a different mindset to navigate. Get it wrong, and one of offsite’s key benefits – shorter construction time – is at stake. Get it right and the quality and schedule gains are tremendous.
“Rather than thinking of the proposed building’s location as a construction site, think of it as part of a manufacturing facility that just happens to be in the client’s location”
Building using offsite methods is not necessarily harder, but it is different. It requires a completely new approach to construction, one that breaks down traditional barriers between disciplines and project stages into one cohesive operation.
Rather than thinking of the proposed building’s location as a construction site, think of it as part of a manufacturing facility that just happens to be in the client’s location. It’s not so much construction but assembly – the final part of a process that began in the factory.
In turn, contractors should envisage the factory as an extension of their construction site. They need to be trained accordingly to really understand the offsite manufacturing process and get involved. This crossover is already starting to happen as construction companies develop their own manufacturing facilities and installation teams.
When the build does start on site, proper upfront planning, including 3D site scans and virtual builds, are essential if you want to avoid any nasty surprises. None of the offsite construction types, whether panelised cross-laminated timber (CLT), pre-cast concrete, or structural steel, are hard in themselves to get right in the build. But you really do need to have done your homework because offsite construction with its inherent tight tolerances can be far less forgiving than building traditionally, where there is greater flexibility to make things work on site.
“There are no short cuts. There’s only one way to get the most out of it and that’s planning, planning, and when you’ve finished planning, planning just that little bit more.”
Once the prefabricated box arrives, it’s totally finished. You can’t nudge it, notch it or do anything to it. If there’s a problem, it’s not just a matter of thinking on your feet and reaching for the hammer. Your ability to react is not during the build but far earlier on during the design process. And with volumetric construction, if one module is wrong, they all will be, and you’ll need to find a properly engineered solution with all the implications that means for the schedule and logistics.
So yes, the potential gains on-site using offsite manufacture are impressive but only if you put the work in upfront to ensure it goes smoothly on site. There are no short cuts. There’s only one way to get the most out of it and that’s planning, planning, and when you’ve finished planning, planning just that little bit more.
Authored by William Johnston, Senior Director, Structures in Canada and Richard Anderson, Technical Director, Project & Commercial Services in the UK.
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