VC253 Design Brief — Small Second Dwelling Siting Rules

Eligibility in five facts — the rest of that question lives elsewhere

This page is about where a small second dwelling (what most people call a granny flat) can physically sit on a lot and what the plan must contain, once the planning question is settled. The planning question itself — which zones, which conditions, the 300 m² construction trigger, which overlays bite — is answered in our sister guide Granny flats in Victoria without a planning permit: the VC253 rules and, for the group, by the E2ES VC253 guide at e2es.com.au. DollarBuild and E2ES share a founder; that page is the group’s statutory reference for eligibility. Five facts are enough to carry into this one.

—A small second dwelling is a building of 60 m² gross floor area or less, on the same lot as an existing dwelling, used as a self-contained residence with a kitchen sink, food preparation facilities, a bath or shower, and a toilet and wash basin — Clause 73.03 of every Victorian planning scheme, inserted by Amendment VC253 on 14 December 2023.
—Its use needs no planning permit in the main residential and rural zones provided there is no more than one existing dwelling on the lot, it is the only small second dwelling on the lot, and reticulated natural gas is not supplied to it (each zone’s Section 1 table of uses).
—On a lot under 300 m² in the General, Neighbourhood, Residential Growth, Mixed Use, Housing Choice and Transport or Township zones a planning permit is required to construct it and Clause 54 applies — Amendment VC282, in operation 8 September 2025 (Clause 32.08-6 and its equivalents).
—Overlays can require a permit on any lot; the lot cannot be subdivided to put the unit on its own title; and no car space is required, because Clause 52.06 states that it does not apply to the construction and use of a small second dwelling.
—A building permit from a registered building surveyor is always required — and the rules below are the ones that surveyor applies.

Which instrument writes the plan: Part 5 of the Building Regulations 2018

The Building Amendment (Small Second Dwellings) Regulations 2023 (S.R. No. 132/2023) came into operation on 14 December 2023, the same day as VC253. They inserted into regulation 5 of the Building Regulations 2018 a definition narrower than the planning one: a small second dwelling is “a Class 1a building that is self-contained and has a gross floor area that is equal to or less than 60 m² on the same allotment as an existing building that is a single Class 1 building that is not a small second dwelling”. Class 1a is the house classification, so the unit is designed, inspected and certified as a house, not as an outbuilding.

Regulation 72, as substituted, applies the whole of Division 2 of Part 5 — the single-dwelling siting rules — to a small second dwelling “unless the small second dwelling is specifically excluded”. Only three rules are switched off: the maximum street setback (reg 73(5)), car parking (reg 78(7)) and the house-sized private open space rule (reg 86(4)), which reg 86A replaces. Two rules are added: the behind-the-front-wall setback (reg 74A) and the access path (reg 86B). Everything else — height, side and rear setbacks, walls on boundaries, site coverage, garden area, permeability, daylight, overshadowing and overlooking — applies to the unit exactly as it would to a new house.

The regulations do not say how gross floor area is measured. Council guidance does: Cardinia Shire’s fact sheet (October 2025) reads the 60 m² as measured “from the outside of external walls or the centre of party walls”, including all roofed areas. Drawn that way, a 60 m² plan has roughly 54 to 56 m² inside the walls, and a roofed verandah is not free. Confirm the measuring convention with the building surveyor before choosing a plan that sits at the limit.

“Sixty square metres is not the hard part of the brief. The hard part is one metre of clear path at two metres of height from the street to the front door — measure that before you fall in love with a plan.”
Joey Don, Founder & Managing Director, DollarBuild

Rule by rule: regulation, number, and what it does to the plan

The table is the brief. Every row is a rule the surveyor must see satisfied on the allotment plan or the elevations, with the regulation that carries it and the plan consequence that follows. Where a planning permit is also needed — a lot under 300 m², or an overlay — Clause 54 as rewritten by VC282 applies a parallel set of standards, noted in the second column where they exist.

Rule	Instrument	Number	Design consequence
Position on the lot	Reg 74A(1)–(2); Clause 54 Standard A2-8 where a planning permit applies	Behind the front wall of the existing dwelling facing the front street; porches, verandahs, pergolas, eaves, gutters, sunblinds, fixed screens and decks or steps over 800 mm may not encroach	The unit lives in the side or rear yard. On a corner lot only the front street counts (reg 74A(4)), although Table 74 still sets a minimum from the side street alignment on a corner allotment
Maximum street setback	Reg 73(5)	Does not apply to a small second dwelling	The one-third-of-depth rule that stops a house hiding at the back of a lot does not pull the unit forward
Building height	Reg 75	The zone or schedule height if one is set; otherwise 9 m, or 10 m where the natural ground slopes 2.5° or more across a section wider than 8 m	A single-storey unit is far inside; what matters is holding the wall at 3.6 m or below so the next row stays at 1 m
Side and rear setbacks	Reg 79, Table 79; Clause 54 Standard A2-3	1 m where the wall is 3.6 m or lower; 1 m plus 300 mm for every metre over 3.6 m up to 6.9 m; eaves, fascia and gutters may encroach 600 mm, porches, services and tanks 500 mm	A 3.6 m wall sits 1 m off the fence with its 600 mm eaves inside that metre; a raked or two-storey wall pushes the whole building in
Wall on a boundary	Reg 80	On or within 200 mm of a side or rear boundary: no longer than an abutting neighbour’s wall, or 10 m plus 25% of the remaining boundary; average height 3.2 m, maximum 3.6 m	One long blank wall can sit on the rear or side fence; it is then also within 900 mm of the boundary, so it is fire-rated and has no windows (next row)
Fire separation	NCC 2022 Volume Two H3D3 → Housing Provisions 9.2.1, 9.2.3	An external wall less than 900 mm from a side or rear boundary, or less than 1.8 m from another building on the allotment (a garage or shed appurtenant to the house is excluded), must have an FRL of 60/60/60 or be 90 mm masonry, with openings restricted	Either 1.8 m clear between the unit and the house, or a fire-rated wall facing it — the gap is usually the cheaper answer and it also keeps the path open
Site coverage	Reg 76(2), (5); Clause 54 Table A2-5	Buildings must not occupy more than 60% of the allotment, both buildings counted; eaves up to 600 mm and unroofed decks, terraces, patios and pergolas are disregarded. Where a permit applies, Table A2-5 sets 60% (NRZ, TZ), 65% (GRZ) or 70% (RGZ, MUZ, HCTZ)	House plus garage plus unit must fit inside 60% of the lot — the reason large lots take the 60 m² easily and tight lots take the Studio 30
Garden area	Reg 76A(2), (6)	Where the zone sets a garden area (General and Neighbourhood Residential): 25% of a 400–500 m² lot, 30% over 500 to 650 m², 35% over 650 m²; only ground at least 1 m wide counts, and buildings, driveways and parking are excluded	On a 600 m² GRZ lot, 180 m² of garden at least 1 m wide must survive the unit, its path and its terrace
Permeability	Reg 77(2), (4)	At least 20% of the allotment must have a permeable surface, both buildings counted	Choose pervious paving or gravel for the path and terrace when coverage is tight; the plan must show the impermeable areas (reg 25(2)(f))
Car parking	Reg 78(7); Clause 52.06 (does not apply to a small second dwelling)	No car parking space is required for the unit	The driveway does not have to widen; the plan still shows the house’s existing spaces (reg 25(2)(g))
Private open space — the unit	Reg 86A; Clause 54 Standard A3-3	At least 8 m² with a minimum dimension of 1.6 m and convenient access from a habitable room other than a bedroom (Clause 54: from a living area, dining area or kitchen)	The living-room door opens onto a terrace or lawn at least 1.6 m deep — not onto the path
Private open space — the house	Reg 86(2)(b)	The existing dwelling keeps at least 25 m² with a minimum dimension of 3 m at its side or rear, off a habitable room other than a bedroom	The unit cannot take the whole backyard: a strip at least 3 m deep stays with the house
Access path	Reg 86B; Clause 54 Standard A3-5	A clear, unobstructed path from the front street at least 1 m wide (1.8 m if longer than 30 m), 2 m clear height with no encroachments, gradient no steeper than 1 in 14, cross fall no steeper than 1 in 40, sealed or all-weather	The side passage becomes a regulated corridor: hot-water units, meter boxes, air-conditioner condensers, gates and eaves below 2 m are all encroachments, and a step needs a ramp
Neighbours’ amenity	Regs 81–85; reg 69(2)	The single-dwelling daylight, solar-access, overshadowing and overlooking tests apply, and a small second dwelling next door counts as an existing dwelling	Window positions, sill heights and screening on the boundary sides are drawn to the neighbour, not to the view
Report and consent	Building Act 1993 s 188A and Schedule 2 clause 4A; Minister’s Guideline MG-12 (Gazette S677, 14 December 2023)	A design that misses any siting rule needs the council’s consent, decided only against the MG-12 criteria — for reg 74A: streetscape, building envelope, lot shape, slope, solar access, vegetation	Design inside the numbers; a variation is an application with an adjoining owner to hear, not a formality

Where the building can sit on a typical 600 m² lot (illustrative)

Take an illustrative lot of 15 m by 40 m (600 m²) in a General Residential Zone with an existing single-storey house of 150 m² and a 36 m² garage — every figure invented for the arithmetic, not a site assessment. Site coverage allows 360 m² of buildings, so the 186 m² already there leaves 174 m² of headroom: a 60 m² unit lands the lot at 246 m², or 41 per cent, well inside reg 76. Garden area at 30 per cent asks for 180 m² of ground at least 1 m wide that is not building, driveway or parking; permeability asks for 120 m² of pervious surface. Both are comfortable if the terrace and the path are pervious.

Position follows from the table. The unit sits in the rear yard behind the house’s rear wall, which satisfies reg 74A by a wide margin. With walls at 3.6 m or below it sits 1 m off the side and rear fences, or one long wall goes on the rear boundary under reg 80 — the 15 m rear boundary allows 10 m plus 25 per cent of the remaining 5 m, so up to 11.25 m of wall. Between unit and house, 1.8 m of clear ground avoids the fire-rated wall and keeps the path continuous. The house keeps a strip of its own open space at least 3 m deep along one side of the yard; the unit’s 8 m² terrace, at least 1.6 m deep, opens from the living room on the other.

The path is where lots fail. From the front boundary the route runs down the side passage: 1 m of clear width at 2 m of clear height for its whole length. A 1.2 m side setback loses the test to a 300 mm hot-water unit or a meter box; a passage longer than 30 m needs 1.8 m. The gradient limit of 1 in 14 means a 500 mm rise across the yard needs 7 m of run or a ramp, and the cross fall limit of 1 in 40 rules out a path that simply follows a sideways slope. Sealed or all-weather means paving, concrete or compacted gravel, not lawn.

Corner lots, sloping lots, long lots and narrow lots

—Corner lot: reg 74A(1) measures only from the front wall of the existing house facing the front street, and reg 74A(4) says a lot that touches another only at a corner does not adjoin it. Table 74’s minimum setback from the side street alignment still applies on a corner allotment, and MG-12’s consent grounds for reg 74A are written around side-street setbacks, prevailing setbacks and lot shape.
—Sloping lot: the height limit of reg 75 rises to 10 m where the natural ground slopes 2.5° or more, but the path’s 1 in 14 gradient and 1 in 40 cross fall do not relax. Cut, fill, a switchback ramp or a landing sequence is part of the design, and MG-12 lists slope as a ground on which the council may vary reg 74A and reg 86B.
—Long or battle-axe lot: a path longer than 30 m must be 1.8 m wide (reg 86B(1)(a)), wider than most side passages between a house and a fence. A path from a rear street or lane instead of the front street is available only by report and consent under MG-12 siting requirement 17.
—Narrow lot: with a 1 m path on one side, 1 m setbacks, 1.8 m to the house and the house’s own 3 m deep open space, a 30 m² plan is often the one that fits; the width, not the area, is the constraint.
—Lot with a water easement: no structure over an easement in favour of a water authority, or within 1 m of any other authority’s works (5 m for Melbourne Water), without that authority’s consent — Water Act 1989 s 148, restated in the note to reg 130.

Services and energy: not siting rules, but they shape the plan

Three more instruments decide what a compliant 60 m² plan contains. The no-gas condition is planning, not building: reticulated natural gas must not be supplied to the unit, so the plan is drawn all-electric — induction cooktop, electric or heat-pump hot water, reverse-cycle heating — from the first sketch rather than converted later. Energy is the National Construction Code: Sustainability Victoria records that the NCC 2022 update came into effect in Victoria in May 2024, and under Specification 42 a Class 1 building assessed with house energy rating software must achieve at least 7 stars (S42C2) and a whole-of-home rating of not less than 60 (S42C3), satisfying H6P1 and H6P2 through H6D2. On a unit this small, orientation, glazing and eave depth do most of that work, which is why the siting decision and the energy rating are one decision.

Fire and water complete the set. Interconnected smoke alarms are a Class 1a requirement (H3D6 through Housing Provisions Part 9.5). Stormwater must be designed to the council’s legal point of discharge and the council’s report obtained before the permit (reg 133); an unsewered lot needs the council’s report and consent for the septic system (reg 132); and the surveyor sees every easement on the allotment plan (reg 25(2)(a)). None of these changes where the building sits, but each can add a pit, a tank, a trench or a drain that consumes garden area and path width.

What the building surveyor will ask for

Regulation 25 of the Building Regulations 2018 lists what an application for a building permit must carry. For a small second dwelling, read it as a checklist.

—A copy of any planning permit that applies (reg 25(1)(a)) — or, where none is needed, the evidence of that: zone, lot area and the overlay list from the planning certificate.
—Drawings at 1:100 or better — floor plan, elevations, sections, dimensions and structural members — with 1:20 details where needed (reg 25(1)(b)), and the specification of materials and methods (reg 25(1)(c)).
—An allotment plan at 1:500 or better (reg 25(1)(d) and (2)) showing boundaries and easements, the distance to the nearest intersecting street, the unit’s position relative to the boundaries and to the existing house, levels of the lot, floors, street channel and stormwater drain, drains to the point of discharge, the impermeable surfaces for reg 77, the existing car spaces for reg 78, and the private open space for reg 86 and reg 86A.
—Computations and reports that prove compliance (reg 25(1)(f)): slab and frame engineering, the energy rating certificate, a bushfire attack level assessment where the lot is in a bushfire-prone area, and the fire-separation detail for any wall within 1.8 m of the house or 900 mm of a boundary.
—The council’s legal point of discharge report (reg 133), any water-authority consent to build near its assets (reg 130; Water Act s 148), and the septic report and consent on an unsewered lot (reg 132).
—The permit application form now asks “Does the building work relate to a small second dwelling?” (Schedule 4, Form 2, as amended by S.R. 132/2023); an owner-builder’s certificate of consent is simplified by reg 19A; and the occupancy permit at the end is issued under Building Act 1993 s 39.

How the Studio 30, Three-Bedroom 60 and Three-Bedroom 80 are drawn to these rules

The Studio 30 (30 m², one bedroom) and the Three-Bedroom 60 (60 m², three bedrooms) both sit inside the reg 5 definition: self-contained Class 1a buildings on an engineered slab, single storey with walls that hold the 1 m Table 79 setback, specified without a reticulated gas connection, the 60 drawn at the ceiling of the definition rather than above it. The living room is placed so its door opens onto the 8 m² terrace, and the bathroom and laundry share one wet wall so the plan can be mirrored to suit whichever side of the yard carries the path. The building permit and the occupancy permit are inside the delivery scope.

The Three-Bedroom 80 (80 m², three bedrooms, two bathrooms) is deliberately not a small second dwelling. Above 60 m² it is an ordinary second dwelling on the lot: in the General Residential Zone a permit is required to construct a dwelling where one already exists (Clause 32.08-7), assessed against Clause 55 rather than Clause 54 and VicSmart where it meets the listed Clause 55 standards; Clause 52.06 car parking applies at the Table 1 rate for the land’s category; and because it needs a planning permit, the all-electric requirement Sustainability Victoria records for permit-dependent new homes since 1 January 2024 applies. The surveyor then applies the Part 5 siting rules to it as a dwelling, not through reg 74A and reg 86B. It is the plan for lots and states where that pathway is workable and the second bathroom is worth it; the feasibility read states in writing which pathway a lot is on before a proposal is priced.

Questions people ask

What are the siting rules for a granny flat in Victoria?

Part 5 of the Building Regulations 2018 as amended by the Building Amendment (Small Second Dwellings) Regulations 2023: behind the front wall of the existing house (reg 74A), 1 m side and rear setbacks for walls up to 3.6 m (reg 79), boundary walls within reg 80, 60 per cent site coverage and 20 per cent permeability counted across both buildings (regs 76(5), 77(4)), garden area where the zone sets one (reg 76A), 8 m² of private open space (reg 86A), a 1 m wide, 1-in-14 path from the street (reg 86B) and no car space (reg 78(7)). A registered building surveyor applies them at the building permit.

Does a small second dwelling have to be behind the house?

Yes. Regulation 74A(1) requires it to be set back behind the front wall of the existing dwelling that faces the front street, and reg 74A(2) stops porches, verandahs, pergolas, eaves, gutters, sunblinds, fixed screens and decks or steps over 800 mm from encroaching. Where a planning permit applies, Clause 54 Standard A2-8 says the same. A design in front of that line needs the council’s report and consent, decided against the Minister’s Guideline MG-12 criteria — streetscape, building envelope, lot shape, slope, solar access and vegetation.

How far from the side and rear fence must a granny flat be in Victoria?

Table 79 of the Building Regulations 2018: 1 m where the wall is 3.6 m high or less, then 1 m plus 300 mm for every metre of height over 3.6 m up to 6.9 m, then 2 m plus 1 m per metre above that. Eaves, fascia and gutters may encroach up to 600 mm; porches, verandahs, flues, water tanks and heating or cooling units up to 500 mm. A zone schedule can set a different distance, and a wall that complies with reg 80 may sit on the boundary instead.

Can I build the granny flat on the boundary?

Yes, within regulation 80. A wall on or within 200 mm of a side or rear boundary may be no longer than an abutting neighbour’s boundary wall, or 10 m plus 25 per cent of the remaining boundary length, whichever is greater, with an average height of 3.2 m and a maximum of 3.6 m. Because that wall is also within 900 mm of the boundary, NCC 2022 Housing Provisions 9.2.3 requires an FRL of 60/60/60 or 90 mm masonry and restricts openings — so it is a blank, fire-rated wall.

What is the site coverage limit for a lot with a granny flat?

Regulation 76(2) caps buildings at 60 per cent of the allotment unless the zone schedule sets a different figure, and reg 76(5), inserted in 2023, applies the cap to the two buildings together — house, garage and small second dwelling. Up to 600 mm of eaves and unroofed pools, terraces, patios, decks and pergolas are disregarded. Where a planning permit applies, Clause 54 Table A2-5 sets 60 per cent in the Neighbourhood Residential and Township zones, 65 in the General Residential and 70 in the Residential Growth, Mixed Use and Housing Choice and Transport zones.

Does the minimum garden area apply to a small second dwelling?

Yes, where the zone sets one — the General and Neighbourhood Residential zones. Regulation 76A requires 25 per cent of a lot of 400 to 500 m², 30 per cent over 500 to 650 m² and 35 per cent over 650 m², counting only ground at least 1 m wide that is not building, driveway or car parking, and reg 76A(6) applies it whether there is one building on the lot or two. Sheds up to 10 m², eaves to 600 mm, pergolas and unroofed decks under 800 mm do not count as building.

What does 20 per cent permeability mean for the design?

Regulation 77(2) requires at least 20 per cent of the allotment to keep a permeable surface, and reg 77(4) counts both buildings. The allotment plan must show the location, dimensions and area of impermeable surfaces (reg 25(2)(f)). In practice the unit’s path and terrace are drawn in pervious paving or compacted gravel where a lot is close to the limit, which also satisfies the sealed-or-all-weather test for the path in reg 86B(1)(e).

Does a granny flat need a car parking space in Victoria?

No. Regulation 78(7) of the Building Regulations 2018 switches off the two-space rule for a small second dwelling, and Clause 52.06 of the planning scheme states that it does not apply to the construction and use of a small second dwelling. The allotment plan still shows the existing house’s spaces (reg 25(2)(g)). A second dwelling larger than 60 m² is not a small second dwelling, and Clause 52.06 applies to it.

How much private open space must the unit have, and does the house keep its own?

The unit needs at least 8 m² with a minimum dimension of 1.6 m and convenient access from a habitable room other than a bedroom (reg 86A); Clause 54 Standard A3-3, where a permit applies, asks for the same 8 m² and 1.6 m from a living area, dining area or kitchen. The existing house must keep at least 25 m² with a 3 m minimum dimension at its side or rear, also off a habitable room other than a bedroom (reg 86(2)(b)). Both areas are drawn on the allotment plan (reg 25(2)(h)).

What is the access path rule for a small second dwelling?

Regulation 86B: a clear and unobstructed path from the front street that is at least 1 m wide (1.8 m if the path is longer than 30 m), has at least 2 m of clear height with no encroachments, a gradient no steeper than 1 in 14, a cross fall no steeper than 1 in 40, and is sealed or has all-weather access. Clause 54 Standard A3-5 repeats it for permit cases. Meter boxes, hot-water units, air-conditioner condensers, gates and low eaves in the side passage are encroachments.

Why 1 in 14, and what does it mean on a sloping yard?

One in 14 is a rise of 1 unit over 14 units of run — about 4 degrees, the gradient of an accessible walkway. A 500 mm rise between the street and the unit’s door needs at least 7 m of path or a ramp, and the cross fall limit of 1 in 40 stops the path simply following a sideways slope. On a sloping lot the design includes cut, fill, landings or a switchback, and MG-12 lists slope as a ground on which the council may consent to a variation of reg 86B.

How close can the granny flat be to the existing house?

The National Construction Code sets that distance, not the Building Regulations. Under NCC 2022 Volume Two H3D3 and Housing Provisions 9.2.1, an external wall of a Class 1 building less than 1.8 m from another building on the same allotment — other than a garage or shed appurtenant to the house — must comply with 9.2.3: an FRL of 60/60/60 tested from the outside or 90 mm masonry, with openings limited to fire windows and self-closing solid-core doors. Most plans leave 1.8 m clear instead.

How is the 60 m² measured?

The Building Regulations define a small second dwelling by gross floor area of 60 m² or less (reg 5) but do not define how to measure it. Cardinia Shire’s fact sheet (October 2025) reads it as measured from the outside of external walls or the centre of party walls, including all roofed areas. On that reading a 60 m² plan has about 54 to 56 m² inside the walls and a roofed verandah counts. Confirm the convention with the building surveyor before choosing a plan at the limit.

Do the coverage and garden-area rules count the unit and the house together?

Yes. The 2023 amendment inserted subregulations 76(5), 76A(6) and 77(4), each stating that the rule applies whether there is one building on the allotment or two, one of which is a small second dwelling. The site coverage cap, the garden area and the permeability minimum are therefore tested on the whole lot after the unit is added, not on the unit alone.

Do the overlooking and overshadowing rules apply to a granny flat?

Yes. Regulations 81 to 85 — daylight to existing windows, solar access to north-facing windows, overshadowing of recreational open space, overlooking, and daylight to the unit’s own windows — apply to a small second dwelling as to any new Class 1 building, because reg 72 applies the whole Division unless a rule is specifically excluded. Regulation 69(2) also treats a neighbour’s small second dwelling as an existing dwelling, so the tests run to it too.

What happens if the design does not meet one of the siting rules?

Each siting regulation carries its own report-and-consent power: the council must consent before the surveyor can issue the permit. Under Building Act 1993 s 188A and Schedule 2 clause 4A the council decides only against the Minister’s Guideline MG-12 (Gazette S677, 14 December 2023) and must refuse if a guideline matter is not met. For reg 74A the grounds are streetscape, building envelope, lot shape and dimensions, slope, solar access and vegetation; for reg 86B, lot shape and a more appropriate side or rear street path.

What energy rating does a small second dwelling need?

The National Construction Code rating for a Class 1 building. Under NCC 2022 Volume Two Specification 42, assessed with house energy rating software, the building must achieve at least 7 stars (S42C2) and a whole-of-home rating of not less than 60 (S42C3), satisfying H6P1 and H6P2 through H6D2. Sustainability Victoria records that the NCC 2022 update came into effect in Victoria in May 2024. On a 30 or 60 m² plan, orientation, glazing and eaves carry most of the rating.

Can the unit be connected to gas?

No. “Reticulated natural gas must not be supplied to the building” is a condition of the Section 1 no-permit use in each residential zone, so the plan is drawn all-electric from the start. For a larger second dwelling that needs a planning permit, Sustainability Victoria records that new homes requiring a planning permit have had to be all-electric since 1 January 2024. Either way the compliant plan has an induction cooktop and electric or heat-pump hot water.

What must the building surveyor see before issuing the permit?

Regulation 25 of the Building Regulations 2018: any planning permit, 1:100 drawings with 1:20 details, the specification, a 1:500 allotment plan showing boundaries, easements, distance to the nearest intersecting street, the unit’s position relative to the house and the boundaries, levels, drains to the point of discharge, impermeable surfaces, car spaces and the private open space for reg 86 and reg 86A, plus the computations and reports — engineering, energy rating, fire separation, and a bushfire attack level where relevant.

Do the same rules apply to the 80 m² Three-Bedroom 80?

No. At 80 m² it is above the reg 5 definition, so it is an ordinary second dwelling: in the General Residential Zone a permit is required to construct a dwelling where one already exists (Clause 32.08-7), assessed against Clause 55, and Clause 52.06 car parking applies. It can be VicSmart where it meets the listed Clause 55 standards. The building surveyor then applies the Part 5 siting rules to it as a dwelling; reg 74A and reg 86B do not apply because it is not a small second dwelling.

My lot is under 300 m² — which rules apply then?

Both sets. Amendment VC282 (in operation 8 September 2025) requires a planning permit to construct a small second dwelling on a lot under 300 m² in the main residential zones, assessed against Clause 54 — Standard A2-8 behind the front wall, A2-3 setbacks, Table A2-5 site coverage, A3-3 open space and A3-5 access path — and it is VicSmart where the listed standards are met (Clause 32.08-6). The building permit that follows still applies regs 74A, 76, 76A, 77, 79, 80, 86A and 86B.

Are there easement, stormwater and septic rules that change where it can go?

Yes. No structure may be built over an easement in favour of a water authority, or within 1 m of any other authority’s works (5 m for Melbourne Water), without that authority’s consent — Water Act 1989 s 148, restated in the note to reg 130. Stormwater must run to the council’s legal point of discharge, and the council’s report is obtained before the permit (reg 133). On an unsewered lot the septic system needs the council’s report and consent (reg 132).

What is the maximum height of a small second dwelling?

Regulation 75: the height set by the zone or its schedule if there is one; otherwise 9 m, or 10 m where the natural ground slopes 2.5 degrees or more across any section wider than 8 m. The number that matters for a single-storey unit is 3.6 m — the wall height at which the Table 79 setback stays at 1 m, and the maximum height of a reg 80 boundary wall.

Can a Studio 30 fit where a 60 m² plan cannot?

Often. The rules that defeat a plan are widths, not areas: a 1 m clear path at 2 m of height, 1 m setbacks for walls up to 3.6 m, 1.8 m to the house or a fire-rated wall, and the house’s own 25 m² by 3 m open space. On a narrow or already built-out lot a 30 m² plan can meet all four where a 60 m² plan cannot. The feasibility read draws both on the allotment plan before a proposal is written.

References

1.Building Regulations 2018 (Vic) — Authorised Version No. 031, incorporating amendments as at 1 September 2026 (regs 5, 25, 69, 72–80, 86, 86A, 86B, 130–133) — checked 19 September 2026
2.Building Regulations 2018 (Vic) — in-force version history (Victorian Legislation) — checked 19 September 2026
3.Building Amendment (Small Second Dwellings) Regulations 2023, S.R. No. 132/2023 — authorised version, in operation 14 December 2023 — checked 19 September 2026
4.Victoria Government Gazette S677, 14 December 2023 — Minister’s Guideline MG-12: siting and design of single dwellings under Building Act 1993 s 188A (siting requirements 3 and 17) — checked 19 September 2026
5.Victoria Government Gazette S414, 11 August 2025 — Amendment VC282, in operation 8 September 2025 (Clause 54; 300 m² construction trigger) — checked 19 September 2026
6.Victoria Planning Provisions — Clause 73.03 Land use terms, definition of small second dwelling — ordinance text read through the planning API, 19 September 2026
7.Victoria Planning Provisions — Clause 32.08-6 Construction and extension of a small second dwelling on a lot (VC282; VicSmart standards list) — ordinance text read through the planning API, 19 September 2026
8.Victoria Planning Provisions — Clause 32.08-7 Construction and extension of two or more dwellings on a lot (VC300; Clause 55) — ordinance text read through the planning API, 19 September 2026
9.Victoria Planning Provisions — Clause 54.02 Neighbourhood character (Standards A2-3, A2-5 with Table A2-5, A2-8) — ordinance text read through the planning API, 19 September 2026
10.Victoria Planning Provisions — Clause 54.03 Liveability (Standards A3-3 and A3-5) — ordinance text read through the planning API, 19 September 2026
11.Victoria Planning Provisions — Clause 52.06 Car parking (does not apply to the construction and use of a small second dwelling) — ordinance text read through the planning API, 19 September 2026
12.NCC 2022 Volume Two — Part H3 Fire safety, H3D3 Fire separation of external walls; H3D6 smoke alarms — checked 19 September 2026
13.NCC 2022 Housing Provisions — Part 9.2 Fire separation of external walls (9.2.1 to 9.2.6) — checked 19 September 2026
14.NCC 2022 Volume Two — Part H6 Energy efficiency, H6D2 — checked 19 September 2026
15.NCC 2022 Volume Two — Specification 42 House energy rating software, S42C2 (7 stars) and S42C3 (whole-of-home rating 60) — checked 19 September 2026
16.Sustainability Victoria — Seeing 7 stars: new home energy efficiency standards explained (NCC 2022 in effect in Victoria from May 2024; all-electric for permit-dependent new homes from 1 January 2024) — checked 19 September 2026
17.Water Act 1989 (Vic) — s 148 structures over easements or near water authority works (version 147) — checked 19 September 2026
18.Building Act 1993 (Vic) — s 39 occupancy permits; s 188A and Schedule 2 clause 4A report and consent (version 152) — checked 19 September 2026
19.Cardinia Shire Council — Small Second Dwellings fact sheet, Version 1, October 2025 (gross floor area measurement; no car parking requirement) — checked 19 September 2026

Studio 30 Three-Bedroom 60 Three-Bedroom 80

VC253 as a design brief: what the 60 m² small second dwelling rules mean for the plan on your lot