Manufacturing and consent: Issues with prefabrication at scale
This month in our Prefab series we take a glimpse at how the current building consent regime applies to prefabrication at scale – manufacturing at home or offshore.
Manufacturing homes at scale – Multiproof
The Building Act 2004 provides for what is commonly referred to as MultiProof approval. If a manufacturer plans to replicate the same or similar standardised building design many times, sections 30A-20H of the Building Act cover a national multiple-use approval statement by the Ministry of Business, Innovation and Employment (MBIE). MultiProof approval is well placed to provide an efficient consent process for prefabricated buildings.
Conditions for MultiProofs include building an approved MultiProof design at least 10 times over two years.
While each prefabricated building still requires building consent from a local authority, the MultiProof speeds up the consent process. Section 19(1)(ca) of the Building Act provides that a building consent authority must accept a MultiProof as establishing compliance with the Building Code if all relevant conditions of the relevant MultiProof are met. A MultiProof can cover variations in design, so long as they are accounted for in the MultiProof.
Consent for offshore
In Auckland Council v Liaw  NZDC 13532 the District Court was asked whether a code compliance certificate can be issued by a building consent authority that permits the use of prefabricated components for a building where a significant portion of the prefabrication occurred offshore. The buildings were both substantially prefabricated with manufacturing of these components occurring offshore. In both cases, the prefabricated components were specified in the building consent application to be subject to the relevant MultiProof approval.
The Court said there should not be a difference in the consent process whether the prefabricated component is made in New Zealand or offshore – either way the manufacturer should submit to inspection regimes or face not getting a consent or code compliance certificate.
Unfortunately for consenting authorities, the Court did not provide any insight into the circumstances where a consenting authority is asked to certify as code compliant building work containing components manufactured offshore that have not been the subject of an inspection regime.
At scale prefabs and consenting authorities
The possibilities of offshore prefab also pose some interesting questions for the industry and building products:
- What is the compliance cost for importers, and the competitive advantage to importers if compliance is not achieved or enforced?
- What is the cost and risk to consenting authorities and ratepayers of ensuring compliance?
- If a consenting authority owes a duty to purchasers of buildings in New Zealand, does that extend to buildings built offshore but purchased in New Zealand?
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