Streamline OSM systems and details

By - , Build 186

There is a strong case for system and detail standardisation in off-site manufacture (OSM) of timber-framed dwellings, according to Johann Betz, Director of Offsite Design.

THE BENEFITS of off-site manufacture (OSM) are increasingly acknowledged, but despite the housing crisis, New Zealand has few prefabricators capable of supplying the residential market with timber-framed panellised buildings at scale. The failure of some early start-ups shows the complexity of achieving commercial viability as a panellised timber prefabricator.

Moving from the traditional model

The traditional model of building timber-framed houses to NZS 3604 evolved over many years in the absence of modern off-site factories. Now, as interest in prefabrication grows, there are questions to be asked. Is there a prefabricated mode of construction based on NZS 3604 that can offer the benefits of advanced prefabrication? What does advanced prefabrication to NZS 3604 look like? How can New Zealand capitalise on the benefits of off-site manufacture?

New Zealand currently lacks a nationally recognised system, suite of details and construction process that supports panellised prefabrication to NZS 3604.

Barriers for start-ups

Becoming a successful panellised prefabricator is a lengthy process. Apart from developing a market, it requires substantial R&D:

  • Developing a suitable prefab system (open and closed multi-layer panels) with compliant standard details that must be efficient in factory prefabrication and on-site assembly.
  • Developing a suitable operation including prefab manufacturing processes, factory blueprint, factory specifications, machine and software selection and technical feasibility.
  • Developing an in-factory quality assurance (QA) regime to achieve compliance across territorial authorities.
  • Educating developers and designers about the system.

Unfortunately, the residential construction market is fragmented, predominantly comprising small to medium-sized building companies inexperienced in off-site manufacture. These businesses are at a disadvantage when trying to overcome barriers to entry.

Standardise key system and design details

A factory compliance/QA regime and panellised standard details should be developed and disseminated at a national and industry level. This would ensure the wider industry is working to a common standard rather than individual prefabricators each reinventing the wheel.

Standardising some underlying systems and details of panellised prefabrication would help to focus the design, production, assembly and compliance of light timber-framed components.

Designers and developers would know what to design for, including system constraints, and how to optimise their projects for a universal system. Prefabricators would be confident in how their product would look and build a factory accordingly. Compliance would be easier since the prefab systems and QA regime across factories would be streamlined.

As an analogy, just as site-based construction of light timber-framed buildings is focused on NZS 3604, so too the off-site manufacture of closed light timber-framed panels should be standardised as an extension to NZS 3604.

To be clear, I do not propose standardisation of house designs or plans but that standard details and certain aspects of systems in design and manufacture should be developed collaboratively and standardised nationally.

Benefits to the construction industry

Focusing panellised design and prefabrication of timber-framed buildings would have multiple benefits. Short term, it would:

  • enable and speed up prefab start-ups
  • streamline QA and compliance across prefabricators and territorial authorities
  • enable large developers such as Kāinga Ora to optimise their projects for OSM panellised construction, creating topdown demand for a universal system that can be supplied by a variety of fabricators.

Long term, this would transform the industry, moving it into the industrialised production of a diverse range of prefabricated products.

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