Granny flats by the rulebook: what WA, NSW, Victoria and New Zealand now allow

Why the rules moved at once

Governments in Perth, Sydney, Melbourne and Wellington arrived at the same tool for the same reason. Secondary dwellings use land and services that already exist, they can house an ageing parent, an adult child or a tenant, and they can be built by homeowners rather than developers. Every one of the recent reforms is framed around housing supply and choice. None of them, however, is a free pass. Each strips out a particular approval — planning, resource consent or building consent — while keeping the others, and the exemptions are tied to dimensional rules that shape the architecture as much as any site constraint.

The practical consequence for designers is that the first question on a granny-flat brief is no longer “how big can it be?” but “which approval are we trying to avoid, and what does that cost us in design freedom?” A plan that sits one square metre over a threshold, or a deck enclosed on the wrong side, can move a project from a two-week certificate to a months-long assessment.

Western Australia: 70 m² and no planning approval

In WA, revised Residential Design Codes (R-Codes) Volume 1 took effect on 10 April 2024, and from that date an R-Code-compliant ancillary dwelling — the WA term for a granny flat — no longer needs planning approval if it meets the deemed-to-comply provisions and the local scheme’s setbacks, and does not exceed 70 m². The State removed the previous minimum lot size of 350 m², allowed ancillary dwellings on grouped-dwelling and strata lots in all Volume 1 density codes, and dropped the requirement for a separate parking bay except in some densities and car-dependent locations.

The quietly significant change for architects is the deletion of the deemed-to-comply clause that required an ancillary dwelling to be “compatible with the colour, roof pitch and materials” of the main house. A backyard studio in Canning Vale or Fremantle can now be a deliberately different object — a timber pavilion behind a brick-and-tile house — without triggering a design-principles assessment on that point alone. What remains are the deemed-to-comply tests the State lists: setbacks, site cover, height, visual privacy and access. A building permit and National Construction Code (NCC) compliance are still required, and anyone may live in the dwelling, related or not.

WA also connects granny flats to its short-stay regime. The Department of Planning’s guidance treats an ancillary dwelling on the same title as the main house as hosted accommodation, and all short-term rental accommodation in WA has had to be registered since 1 January 2025. For clients who want a guest studio that occasionally earns its keep, that is a useful distinction — but it is a registration obligation, not a design exemption.

New South Wales: 60 m², 450 m² and a long schedule

NSW has the most mature framework and the most arithmetic. Under State Environmental Planning Policy (Housing) 2021, a secondary dwelling is permitted in residential zones R1 to R5 and can be approved either through a development application or, if every standard in Schedule 1 is met, as complying development certified by council or a private certifier. The floor area of the secondary dwelling, excluding an attached ancillary structure, is capped at 60 m² unless another planning instrument allows more.

The complying pathway needs a lot of at least 450 m² (unless the secondary dwelling sits entirely within an existing house), only one principal and one secondary dwelling on completion, and minimum frontages that scale with lot size — 12 m for lots of 450–900 m², 15 m up to 1,500 m², 18 m above that, or a 3 m-wide access handle for battle-axe lots. Site coverage across all buildings is limited to 50, 40 or 30 per cent depending on lot size, and the combined floor area of both dwellings plus attached structures is capped at 330, 380 or 430 m². Schedule 1 also sets landscaped-area minimums, and no additional parking is required.

Two definitions matter at the drawing board. Floor area is measured within the outer face of external walls at 1.4 m above floor level, so wall build-up counts against the 60. And an “attached ancillary structure” — a deck, verandah or pergola enclosed by a wall higher than 1.4 m — joins the floor-area tally, while an open deck does not count towards site coverage. The design lesson is that thick, well-insulated walls and semi-enclosed outdoor rooms both have a measurable price in NSW. If a site falls short on any standard, the project is not dead; it moves to a council development application and a merit assessment.

Victoria: 60 became 80 this month

Victoria’s reform arrived in two steps. Amendment VC253, gazetted on 14 December 2023, introduced the “small second dwelling” and removed the planning-permit requirement for most homes up to 60 m², alongside matching changes to the Building Regulations 2018. In the General Residential, Neighbourhood Residential, Residential Growth, Mixed Use and Township zones, no permit is needed unless the lot is under 300 m²; in the Low Density Residential Zone, none is needed at all. There can be only one existing dwelling and one small second dwelling, the new home must not connect to reticulated gas, and it cannot be subdivided off. Heritage, Neighbourhood Character and Design and Development overlays do not trigger a permit if the building stays under 5 m high and is finished in muted tones; flood and bushfire controls still do, and Green Wedge and Rural Conservation zones always require one.

Then, on 15 October 2026, Amendment VC306 raised the planning cap from 60 m² to 80 m², changed how floor area is measured, and deleted the planning requirement for an access pathway. Under the revised definition the 80 m² is measured from the outside surface of external walls and excludes attached patios, pergolas, porches, terraces and roofed decks or verandahs. Under VC253, the 60 m² was gross floor area including roofed areas — so a covered verandah once ate into the allowance and now does not. That is a genuine design gift: deep verandahs and covered outdoor rooms are back on the table without shrinking the interior.

The caution is timing. Planning Victoria says the corresponding changes to the Building Regulations 2018 and Minister’s Guideline 12 are to follow. Until they do, a 60–80 m² design may qualify as a small second dwelling for planning but not yet under the building regulations, and a building permit is always required. For projects in that band, get the building surveyor’s pathway confirmed in writing before the client signs a construction contract.

New Zealand: no building consent, with conditions

New Zealand went furthest by removing the building consent itself. The Building and Construction (Small Stand-alone Dwellings) Amendment Act 2025 came fully into force on 15 January 2026, and on the same day the Resource Management (National Environmental Standards for Detached Minor Residential Units) Regulations 2025 made a detached minor unit of up to 70 m² a permitted activity — no resource consent — in residential, rural, mixed-use and Māori-purpose zones, provided the standards and any applicable council rules are met.

The building consent exemption is tightly drawn. According to MBIE’s guidance the dwelling must be new, stand-alone and single-storey; no more than 70 m² measured to the finished internal faces of external walls, including any internal garage; at least 2 m from other residential buildings and legal boundaries; framed in light timber or light steel or, since 8 October 2026, a certified composite structural product; clad with walls weighing no more than 220 kg/m²; and without a level-entry shower that needs a waterproof membrane. Design and restricted building work must be done or supervised by Licensed Building Practitioners, and plumbing, drainage, gas and electrical work by licensed trades. The owner applies for a project information memorandum (PIM) before starting, notifies council on completion with records of work and certificates, and may pay a development contribution. The build must be completed within two years of the PIM, unless council grants an extension.

MBIE estimated the exemptions could save up to NZ$5,650 in direct costs and up to 14 weeks. The trade-off for architects is clear from the conditions: no second storey, no heavy masonry skins, no membrane-dependent level showers, and setbacks measured — following a September 2026 amendment to the national standard — from the exterior face of wall cladding. Anything more ambitious goes back through the consent system, which remains available.

What this means at the drawing board

Read side by side, the four regimes reward the same disciplines. Measure early and measure the way the rule measures: external face in NSW and Victoria, internal faces in New Zealand, internal floor area in WA. Decide where outdoor rooms sit, because a verandah is free in Victoria since VC306 but an enclosed deck can count in NSW. Treat setbacks as a design generator rather than a residual — the NZ 2 m rule and WA’s local scheme setbacks will often fix the footprint before anything else does. And check hazard overlays first: bushfire and flood controls are the most common reason a “permit-free” granny flat ends up with a permit after all.

Pros: faster, cheaper approvals for compact, well-detailed buildings; more freedom of expression in WA now the compatibility clause is gone; covered outdoor space no longer penalised in Victoria; a national, consistent framework in New Zealand.

Cons: thresholds that do not align across borders; building and planning rules out of step in Victoria for 60–80 m²; narrow construction and storey limits in New Zealand; and, everywhere, the NCC or NZ Building Code still applies in full. The exemptions remove paperwork, not responsibility — which is exactly why a small building with an architect behind it still matters.