Two Systems, One Project
The NCC sets minimum technical standards for building performance across Australia. But building and planning are constitutionally state and territory matters. This means every prefabricated module installed under a planning scheme has to navigate a second — sometimes third — layer of regulatory requirements that sits entirely outside the NCC.
This is where most prefab projects run into trouble. Not because the rules are unclear, but because applicants assume the NCC is the whole story. It isn't.
In Victoria, a prefabricated dwelling or module must navigate two parallel frameworks that operate independently of each other.
Administered under the Building Act 1993 and Building Regulations 2018. This governs building permits, mandatory inspections, and the technical standards a structure must meet. A Registered Building Surveyor (RBS) is the statutory authority within this system — responsible for issuing the building permit and ensuring compliance at each mandatory inspection stage.
Administered under the Planning and Environment Act 1987 and the Victorian Planning Provisions (VPP). This governs land use and built form — whether what you want to build is permitted on that specific piece of land, under that specific zone and overlay.
A building permit does not override a planning requirement. A planning permit does not substitute for a building permit. Both must be satisfied, in the right sequence, before a compliant structure can be erected.
Planning Overlays — The Invisible Filter
A planning overlay is a layer of additional requirements mapped over specific areas of land. They are publicly searchable through the Victorian Planning Information System — but most buyers and many smaller developers don't check them before committing to a prefab product.
The overlays most commonly encountered in Victorian prefab projects:
Imposes specific construction requirements under AS 3959, based on the Bushfire Attack Level (BAL) rating for the site. This has direct implications for cladding specifications, glazing, and external wall assemblies in prefab modules. A module designed to a standard specification may not comply with BMO requirements without modification — and that modification needs to be engineered and documented.
May require minimum floor levels and specific structural assessments affecting module design and anchoring systems. A volumetric module with a fixed floor level may need to be redesigned or elevated to satisfy flood overlay requirements on a given site.
Can restrict height, setbacks, and built form in ways that affect how a volumetric module can be configured on a specific site. A module that works perfectly on one residential lot may require significant design modification — or may be entirely impermissible — on a lot subject to a DDO.
May trigger permit requirements that add assessment time and conditions to the project programme. This affects timeline planning, not just cost.
The Sequencing Problem
Conventional construction has a natural checkpoint for overlay compliance: the design process. An architect or draftsperson designing a house from scratch will typically check the planning scheme as part of site analysis.
Prefab introduces a different risk. A buyer selects a product — a module, a bathroom pod, a volumetric dwelling — and then attempts to install it on a specific site. The product was designed independently of that site's overlay requirements.
This sequencing mismatch is one of the most consistent sources of compliance failure in the Australian prefab market. The product is compliant. The site has requirements the product doesn't meet. The buyer finds out after the contract is signed.
The solution is site-first compliance analysis — understanding what the planning framework requires for a specific site before selecting or committing to a prefab product. In conventional construction, this is standard practice. In the prefab market, it is still the exception.
A Practitioner Note
As a Registered Building Surveyor practising in Victoria, I encounter this sequencing problem regularly. The building permit application arrives with a module specification that hasn't been checked against the planning scheme. The overlay issue surfaces at the permit stage — at which point the project is already committed, the product is often already ordered, and the cost of correction is real.
The question I'd encourage any prefab buyer or developer to ask before signing anything: what overlays apply to this site, and has the product been assessed against them?
If the vendor can't answer that question, someone else needs to.
A condensed version of this series was originally published on LinkedIn on 31 March 2026.
The views expressed are solely those of the author in a personal capacity. This does not constitute legal, building, or professional advice. Readers should seek independent professional advice regarding their specific circumstances.