NZ Prefab CoLab 2019

It’s a curious fact that our trans-Tasman cousins are more advanced that Aussies in many ways. Prime Ministers, yachting, mountains, and off-site manufacturing. Why this is so is a field of enquiry I would like more time to explore, but for now let’s concentrate on just the prefabrication of buildings.

We often complain about the tyranny of distance combined with a relatively small market size in Australia holding back investment in the tooling to make off-site fabrication more cost effective. While Aotearoa is a lot smaller, the winding roads don’t exactly lend themselves to trucking big modules across hilly terrain, so that argument seems not to have been a barrier there. Weather – and let’s face it, they really do get ‘four seasons in one day’ (thanks Crowded House, surely my favourite Kiwi export), so building under a factory roof has obvious advantages. So much so that it is now almost standard practice there to scaffold over the whole building – roof and all – and shrink-wrap in plastic, keep the elements at bay. This must add considerably to conventional site-build costs, so is one factor tipping the scales to off-site building.

But there is more to it than that. There seems to be an underlying enthusiasm for innovation that drives designers and builders to always look for smarter, better, faster, cheaper, higher performance systems and detailing. One company in Wellington makes prefabricated bathroom modules that slot into whatever building shell you like, with finishes and fixtures the equal of anything I have ever seen, yet at a cost of about $15,000 for a typical small bathroom. While not all that much cheaper than a conventional bathroom fitout, add in the speed of installation – 2 hours – and you have some real savings.

We inspected a multi-unit housing development being built for the NZ Sept of Housing, using a combination of prefinished CLT exterior wall panels, CLT floors, and conventional timber framed internal walls. The developer opted for the least cost system for each component, without being wedded to any particular system or tribal design-thinking. That’s innovation right there! All doors and windows are air tight and double glazed of course, and proper building science has been applied to controlling water and moisture flows through walls, by installing truly breathable water barriers rather than standard foil sarking, which has a dreadful record of causing condensation and mould problems in NZ. While most Australian climate zones are a bit more forgiving, the physics is the same, and in recent years and to this day we are still building mould time bombs.

It’s great to see so much cooperation across The Ditch, and the conference name ‘CoLab’ was an intentional double entendre. The Kiwi experience of leaky building syndrome, and mould problems have informed their detailing such that the way they build now is very different to a decade ago. We need to get the mainstream Australian industry up to speed with the same knowledge, quickly. But more than that, the degree of innovation in off-site construction techniques is quite inspiring to be part of. Come on, Aussie, come on – catch up to the Kiwis!