Part 5 Siting Calculator

Before you rely on a figure

What these calculators do and do not decide.

Scope. Division 2 of Part 5 applies to the construction of a single Class 1 building — including a small second dwelling — and any associated Class 10a buildings (reg 72). Two dwellings on one allotment, other than a small second dwelling, are a planning matter and outside these provisions.
The reg 68 gate. A regulation in Part 5 does not apply at all where a planning permit is required for the construction and the planning scheme regulates the same siting matter (reg 68). These calculators assume no planning permit is required for the work.
Zone schedules come first. For minimum street setbacks, building height, site coverage, permeability, side and rear setbacks, boundary walls and private open space — regs 74 to 77, 79, 80 and 86 — a schedule to a zone specified in Schedule 6 can set its own figure, and where it does, that figure replaces the default calculated here. Regs 73, 74A and 78 carry no such override. Check the schedule to the zone before the default.
Approved building envelopes. A design consistent with an approved building envelope is taken to comply with the regulation that deals with the same siting matter (reg 71(1)). But under reg 71(2), where an adjoining allotment is not subject to the same agreement or certified plan of subdivision, the override does not apply to regs 79 to 84 (or the fence equivalents) against that allotment — the estate-edge trap.
How the measurements run. A setback is a horizontal distance (reg 5). Height is measured from natural ground level — for a wall, from natural ground level at the base of the wall to where the outer wall meets the plane of the top of the roof covering or the top of the parapet, whichever is higher (reg 5). Not from the slab, the pad or the finished floor.
"Habitable room" is not defined in regulation 5. In practice the BCA Volume Two sense is applied — living areas, bedrooms, kitchens and the like, as distinct from bathrooms, laundries and storage. Where the classification of a room is arguable, treat it as a question for the relevant building surveyor.
Tolerances. Regulation 7 requires prescribed numerical values to be applied subject to tolerances according to any adopted code or standard, normal trade practice or good practice. A design sitting within a few centimetres of a threshold is a judgement, and the calculators flag it rather than declaring a side.
Non-compliance is usually not a dead end. With one exception, every provision on this page carries its own consent route: the report and consent of the relevant council must be obtained to an application for a building permit for a design that does not comply. The exception is reg 76A — minimum garden area has no consent route, so a shortfall there is a redesign, not an application. Our report and consent guide covers how that runs.

These are calculations over what the Regulations say, read against the figures you enter. They are not a determination under the Building Act 1993, they do not appoint a building surveyor and they do not create a client relationship. Whether a design complies is determined by the relevant building surveyor on the drawings, the site plan and the title.

Regulation 79

Side and rear setbacks.

Table 79 pairs the height of the building at a point with the minimum setback at that point — a profile along the wall, not one number per building. Enter the height at the point you are checking. Walls that comply with reg 80 are excluded entirely (reg 79(5)) — test those in the boundary-wall calculator below.

The calculator needs JavaScript, but the rule does not: the full Table 79 figures and the encroachment lists are written out below.

Regulation 80

Walls and carports on boundaries.

Reg 80 reaches a wall on or within 200 mm of a side or rear boundary, and a carport on or within 1 m of one that is open on the side facing the boundary. It caps the length against each boundary and the height of what is built there. The length limit includes any existing wall or carport already on that boundary — the cap is on the combined length.

The calculator needs JavaScript, but the rule does not: reg 80's length and height limits are written out below.

Regulation 84

Overlooking.

Reg 84 is a geometry test with escape routes, not a setback. A habitable room window or raised open space must not give a direct line of sight into a neighbour's habitable room window or onto their secluded private open space within the regulated envelope — and if it does, one of the compliance routes has to close it. Answer the questions and the checker names the routes that remain open.

The checker needs JavaScript, but the rule does not: the sight-line geometry and every compliance route are written out below.

The rules themselves

The three provisions in full.

The same figures the calculators use, written out — so the page answers with scripting off, and so you can check the calculator against the rule rather than the other way round.

Reg 79 — side and rear setbacks

Unless a schedule to a Schedule 6 zone specifies its own minimums (reg 79(1)), a building must be set back from a side or rear boundary not less than Table 79 (reg 79(2)):

Table 79 — side and rear setbacks
Building height at any point	Minimum setback from a side or rear boundary at that point
3.6 m or less	1 m
More than 3.6 m but not more than 6.9 m	1 m plus 300 mm for every metre of height over 3.6 m
More than 6.9 m	2 m plus 1 m for every metre of height over 6.9 m

May encroach into the setback (reg 79(3)): landings with an area of not more than 2 m² and less than 1 m high, unroofed stairways and ramps, pergolas, shade sails, eaves, fascia and gutters where the encroachment is not more than 600 mm, and carports that comply with reg 80. May encroach by not more than 500 mm (reg 79(4)): porches and verandas, masonry chimneys, sunblinds, permanent and fixed screens under reg 84(5)(d) or (6), flues, pipes and rainwater heads, domestic fuel and water tanks, and heating and cooling equipment and other services.

Reg 79 does not apply to a wall that complies with reg 80 (reg 79(5)). For a design that does not comply, the report and consent of the relevant council must be obtained (reg 79(6)).

Reg 80 — walls and carports on boundaries

Applies to a wall of a building on or within 200 mm of a side or rear boundary, and to a carport on or within 1 m of a side or rear boundary that is open on the side facing the boundary (reg 80(1)).

Length. Unless a zone schedule sets its own maximum (reg 80(2)), the length of the wall, or the carport, or the wall and carport — or any of those combined with an existing wall or carport — must not exceed the greater of: the length of an existing wall or carport on the adjoining allotment within 200 mm of the boundary, where the proposal abuts it; and 10 m plus 25% of the remaining length of the boundary of the adjoining allotment (reg 80(3)).

Height. An average of not more than 3.2 m — calculated after excluding any length of wall less than 2 m in height — and a maximum of 3.6 m (reg 80(4)). A wall or carport abutting an existing wall or carport may instead be built to the height of what it abuts (reg 80(5)).

Two consequences elsewhere: a wall complying with reg 80 is outside reg 79 altogether (reg 79(5)), and under reg 75(3) any part of the building within 1 m of the boundary adjacent to the wall must stay under the plane from the top of the wall to 3.6 m at a 1 m setback. For a design that does not comply, the report and consent of the relevant council must be obtained (reg 80(6)).

Reg 84 — overlooking

A habitable room window or raised open space of a building must not provide a direct line of sight into a habitable room window, or onto a secluded private open space, of an existing dwelling on an adjoining allotment (reg 84(1)).

The envelope. From a window, the line of sight is any line from a height of 1.7 m above floor level, within a space enclosed by vertical planes at 45° from each side of the window, a horizontal plane 1.7 m above floor level, the ground below, and a horizontal distance of 9 m from the window (reg 84(2)). From a raised open space, any line from 1.7 m above floor level along its perimeter to any point within 9 m, extending 45° beyond any point where the perimeter meets a wall (reg 84(3)). For a secluded private open space, the 9 m is measured from ground level (reg 84(4)).

A window complies if (reg 84(5)): it is offset at least 1.5 m, edge of one window to edge of the other; or its sill is at least 1.7 m above floor level; or it has obscure glazing in any part below 1.7 m above floor level — openable only where opening it does not restore the direct line of sight (reg 84(7)); or the line of sight is obscured by a permanent and fixed screen with no more than 25% of its area open. A raised open space complies if the line of sight is obscured by the same kind of screen (reg 84(6)).

New work facing a boundary is outside the regulation where there is a visual barrier at least 1.8 m high at the boundary and the floor level of the room or raised open space is less than 800 mm above the ground level at the boundary (reg 84(8)). Raised open space means a landing of more than 2 m², a balcony, a terrace, a deck or a patio; secluded private open space is private open space screened for at least 90% of its perimeter by a barrier at least 1.5 m high with no more than 25% of its area open, primarily intended for outdoor recreation (reg 84(10)). For a design that does not comply, the report and consent of the relevant council must be obtained (reg 84(9)).

The rest of the Part

Part 5, Division 2 and 3 at a glance.

The default figures where no zone schedule intervenes, one line each. Every one of these provisions except reg 76A carries its own report and consent route for a design that does not comply — minimum garden area alone has none.

Part 5 Division 2 and 3 defaults
Reg	Matter	The default rule
73	Maximum street setback	Not more than one-third of the allotment depth from the front street alignment, unless the allotment is 0.40469 ha or more. Battleaxe allotments measure from the common boundary with the front allotment.
74	Minimum street setbacks	Table 74: the average front setback of existing dwellings on the adjoining allotments facing the same street, or 9 m, whichever is less; with one adjoining dwelling, that setback or 9 m, whichever is less; with none, 6 m on a declared road and 4 m on any other street. Corner side street: match the adjoining dwelling facing the side street or 2 m, whichever is less; else 2 m. Porches, verandahs and pergolas under 3.6 m, eaves, sunblinds, screens, and decks or landings under 800 mm may encroach up to 2.5 m. For this regulation, street excludes a lane, footway, alley or right of way.
74A	Small second dwellings	Set back behind the front wall of the existing dwelling facing the front street.
75	Building height	Not more than 9 m — 10 m where the slope of natural ground level at any cross-section wider than 8 m is 2.5° or more. Beside a reg 80 boundary wall, parts within 1 m of the boundary stay under the plane from the top of the wall to 3.6 m at 1 m.
76	Site coverage	Buildings not more than 60% of the allotment. Up to 600 mm of eaves, and unroofed pools, spas, terraces, patios, decks and pergolas, are disregarded.
76A	Minimum garden area	Only where the zone specifies it: 25% of allotments of 400 m² or more up to 500 m², 30% over 500 m² up to 650 m², 35% over 650 m². The one Division 2 provision with no report and consent route.
77	Permeability	At least 20% of the allotment permeable.
78	Car parking	Two spaces for a new Class 1 building: one at least 6 m × 3.5 m, one at least 4.9 m × 2.6 m; 5.5 m total width where they adjoin in a garage or carport; a building may project over a space at 2.1 m clearance or more.
79	Side and rear setbacks	Calculated above.
80	Walls and carports on boundaries	Calculated above.
81	Daylight to existing habitable room windows	A light court of at least 3 m² with a 1 m dimension clear to the sky — the neighbour's land can count. A wall or carport averaging over 3 m high, within a 55° arc of the window's centre, sits back at least half its height; the arc may swing to not less than 35° from the window's wall plane.
82	Solar access to north-facing windows	Where an existing north-facing habitable room window is within 3 m of the boundary and below the proposed eaves or parapet: 1 m setback at heights to 3.6 m, then 1 m plus 600 mm per metre over 3.6 m, then 3 m plus 1 m per metre over 6.9 m — held for 3 m each side of the window. North-facing means the window's axis points between true north 20° west and true north 30° east.
83	Overshadowing	The required minimum area of a neighbour's recreational private open space — the lesser of 75% of it, and 40 m² with a 3 m dimension — keeps at least 5 hours of sunlight between 9 a.m. and 3 p.m. on 22 September. Where it already gets less, no further reduction.
84	Overlooking	Checked above.
85	Daylight to new habitable room windows	Each new habitable room window faces an outdoor space or light court of at least 3 m² with a 1 m dimension clear to the sky on the same allotment, or a verandah, porch, deck or balcony open for at least a third of its perimeter, or a carport with two or more open sides open for at least a third of its perimeter.
86	Private open space	At least 80 m² or 20% of the allotment, whichever is less, including a side or rear area of at least 25 m² with a 3 m dimension and convenient access from a habitable room other than a bedroom. With a small second dwelling on the allotment, the existing dwelling keeps the 25 m² side or rear area; a small second dwelling itself needs 8 m² with a 1.6 m dimension (reg 86A).
87	Class 10a siting	A Class 10a building appurtenant to a building of another class sits on the same allotment as it, unless approved under the Subdivision Act 1988.

Every figure on this page — the three calculators, the provisions in full and this table — was read against the Building Regulations 2018, Authorised Version No. 030 (as at 1 July 2026), from the authorised PDF, regulation by regulation. Division 4 (fences, regs 88 to 97) is not covered here. Part 5 is amended from time to time — if you are reading this well after that date, ask us to confirm the current text.