Arrow: Design for Manufacture and Assembly in action

111 Dixon Street, Wellington

Costs are rising sharply in many of New Zealand’s construction markets – New Zealand saw a national average increase of 7% compared to last year and a 17% increase in Auckland. These increased costs are really starting to bite into the viability of new apartment developments, particularly as property prices appear to no longer be increasing at rates that mitigate against increases in construction costs.

Corelogic, NZ’s leading provider of property information and analytics services, in their latest research report shows that New Dwelling Consents continue to trend down in Auckland and are flat lining elsewhere. “There are many reasons why the construction industry in Auckland is struggling to build enough houses fast enough, capacity constraints and high costs to build are among them and the problem is not easily or quickly resolved.”1

The capacity constraints Corelogic refer to are only going to get worse given the plans to build tens of thousands of social and affordable units, particularly in Auckland.

PrefabNZ and Arrow believe that innovative technology and offsite manufacturing have a significant and valuable role to play in meeting the challenges the New Zealand construction industry faces in meeting the demand for quality, warm and affordable housing.

However for prefabrication to be successful, from day one of the design process, the use of prefabricated technology needs to be a key consideration – a process referred to as DfMA or Design for Manufacture and Assembly. This design approach optimises the use of offsite manufacturing capability so that building components are delivered on site not to be built, but to be assembled or installed.

Arrow’s latest development project at 111 Dixon Street is an example of where the DfMA approach has been used – albeit in a 20-storey apartment tower. Designed by PrefabNZ member Archaus Architects, the project’s principal prefabricated component will be 228 high quality, manufactured bathroom pods. The building has been designed to optimise their installation.

The structural design eliminates the need to prop the floors for 14 days after they are poured. This means that the bathroom pods can be lowered directly into place and connected, before the next floor above is poured – a huge programme saving in terms of both floor and apartment fitout cycles.

At the very first design meeting, Arrow set the goal of designing the building for the use of volumetric components, and are now looking to benefit from the programme, cost, quality and safety advantages prefabricated construction brings.

In addition to the bathrooms, all 47 balconies will be manufactured offsite and craned into place. The plumbing system will also be modular.

With 100 of the 120 apartments sold Arrow are expecting to start construction in September.

1 Corelogic New Zealand Monthly Property Market & Economic Update, July – August 2017

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