Methodology · Glossary

Glossary.

Plain-language definitions for every metric, acronym, and convention used across the Atlas.

Section 1

Scope & geography

Greater Capital City Statistical Area GCCSA: The official metropolitan region for each capital, defined by the Australian Bureau of Statistics. It’s wider than our 20km analysis area—especially for Sydney and Melbourne—and we use it for the whole-of-metro figure shown beside each 20km headline, so you can see how the result changes across the wider region.
Significant Urban Area SUA: The connected built-up area of each city—its suburbs and town centres—stopping before the semi-rural fringe, also defined by the ABS. Our city maps are drawn to this boundary and our housing-approvals figures are measured at this level. Headline restriction shares are still measured within the 20km analysis area.
20km analysis area: The standard scope for every headline figure. All eight capitals are measured within a 20km radius of a central city landmark, so each is measured the same way regardless of where its council boundaries happen to fall.
City-centre landmark: The single point each city’s distances are measured from—usually a main railway station (Sydney’s Central, Adelaide Station, Brisbane’s Roma Street) or, where there’s no central station, the city’s General Post Office (Hobart, Darwin).
Ring: A one-kilometre-wide band around the city-centre landmark, used to show how restriction changes with distance from the centre. Rings run from the innermost 0–1km band outward; headline figures stop at 20km, while the rankings and comparison tools reach 30km.
Suburb SAL: An official ABS suburb boundary (formally a “Suburb and Locality”). We cover 2,374 suburbs across the eight capitals—behind the per-suburb leaderboard and the suburb detail pages.
Statistical Area Level 2 SA2: A standard ABS statistical area, each roughly 3–25km². We cover 1,322 of them across the eight capitals—a level that lines up cleanly with other official datasets such as the census.
Local Government Area LGA: A council boundary. We cover 137 council areas across the eight capitals—the level at which most planning and zoning decisions are actually made.

Section 2

The headline metric

Highly restricted: Our flagship measure. A parcel of residential land is highly restricted if at least one of four planning controls applies: a cap of no more than 2 storeys, low-density-only zoning, a detached-houses-only rule, or a heritage overlay. (The detached-only rule almost always overlaps the other two, so it rounds out the definition without changing the number much.) Rural-residential land on the city fringe is removed from both sides of the calculation, so the figure reads as “of metropolitan residential land, X% is highly restricted”. It’s deliberately conservative: a parcel only counts as height-capped where a limit is actually published, so land with no published height rule is treated as not capped. The headline therefore under-counts restriction where height data is sparse (notably Perth, and parts of NSW and the Northern Territory)—it never over-counts it.
Excluding heritage: The same measure with heritage-protected land set aside, so you can see how much land is locked up by zoning and the 2-storey cap alone—the land where simply lifting planning controls would directly permit townhouses and mid-rise apartments.
All residential land (including rural): An alternative cut that keeps the rural-residential fringe in the calculation, on both sides. It’s available on the data and comparison pages, and in most cities differs from the headline by only about a percentage point, since rural land is a small share of the total.
Cumulative share: When several 1km rings are combined into one figure, this is the land-area-weighted share—total restricted land divided by total residential land across the rings—rather than a simple average of each ring’s percentage. The two differ because each ring is a 1km band, and bands further out enclose more land.

Section 3

The four controls behind the headline

Cap of no more than 2 storeys: The share of residential land where local planning rules cap buildings at no more than two storeys. A parcel only counts as capped where its height limit is actually published; land with no published limit is treated as if it allows more—so this is a deliberate undercount, not a guess. It’s where our headline most cautiously understates restriction, and the effect is largest where height data is sparse, such as inner Perth and central Darwin.
Low-density only: The share of residential land zoned for low-density use only—the lowest-intensity tier of each state’s residential hierarchy. Exactly what’s allowed varies by state, but the common thread is rules that keep buildings small and spread out: height caps, large minimum lot sizes, and limits on how many homes per block. We map each state’s low-density zones onto one consistent definition so the eight capitals compare fairly.
Detached-only dwelling mandate: The share of residential land where only detached houses are permitted—nothing denser, such as a townhouse or two homes side by side. We count a parcel as detached-only only where there’s no legal route to build anything denser (granny flats and secondary dwellings don’t count as denser). Because this land sits almost entirely within the low-density and 2-storey controls, it adds little to the headline on its own.
Heritage overlay: The share of residential land under any heritage overlay, whether listed by the state or the local council. A parcel counts as heritage when its centre sits inside a heritage area rather than merely touching the edge—a deliberately conservative test that avoids over-counting heritage at the margins.
Rural-residential land: A subset of the low-density bucket covering rural-living and rural-settlement zones—the large-lot “hobby farm” fringe rather than the suburban land most relevant to housing supply. Cities differ enormously: rural land is roughly 78% of residential land in Darwin, around 59% in Hobart and 36% in Brisbane, but close to none in Melbourne and Canberra. Our headline removes this fringe from both the restricted land and the residential total, so the figure describes ordinary suburban land rather than being skewed by large blocks. It’s also a toggle on each city’s zoning map.
Mid-rise permitted: The opposite view of the 2-storey cap: the share of residential land where buildings above two storeys are allowed. Same underlying data, framed as what’s permitted rather than what’s restricted.

Section 4

Reforms

Townhouse Code: A hypothetical national reform that would make three-storey housing legal on residential land currently held back by either a cap of no more than 2 storeys or low-density-only zoning. Heritage overlays would stay. One lever lifts both limits where they apply, so it unlocks every parcel held back by either rule—but not parcels protected by heritage. On the reforms page we report the net new homes this would permit over today’s rules, scored lot by lot.
Mid-rise everywhere: A reform that would make eight-storey mid-rise legal on all residential land not under a heritage overlay—lifting the 2-storey cap and low-density-only zoning together. We report the net new homes over today’s rules, scored lot by lot; the calculator’s custom mode also lets you set your own homes-per-hectare assumption.
Mid-rise on transit: A reform that would make eight-storey mid-rise legal only on non-heritage residential land within 800m of a rapid-transit stop, concentrating new capacity along well-served corridors. We report the net new homes over today’s rules, scored lot by lot.
Public-transport proximity: How restrictive zoning lines up with access to frequent public transport. We measure residential land within 800m of a rapid-transit stop that’s also restricted—by a 2-storey cap, low-density-only zoning, or a heritage overlay—and ask: of all the residential land near rapid transit, how much is locked up? It captures the policy question of how much well-located, transit-rich land is kept off-limits to more homes.
Rapid transit: Stops frequent enough to count toward our public-transport-proximity measure. A stop qualifies if services arrive on average at least every 15 minutes across the weekday daytime window (7am–7pm). How that’s counted depends on the mode. For buses, trams and ferries, a single route at the stop must hit the threshold on its own—riders heading to different places can’t just board whichever vehicle turns up. For trains and metro, all arrivals at a station are treated as one combined service, reflecting how people actually use a busy line. Coverage varies: rail-heavy cities (Melbourne, Sydney, Brisbane) capture more of their network than bus-reliant ones (Canberra, Hobart).
Brisbane rail (data note): A legally protected strike on Queensland Rail from May 2026 cut services by roughly 20% (a Saturday timetable, until further notice). The timetable currently published reflects that reduced service, which would overstate waiting times and understate Brisbane’s frequent-rail coverage. To keep the rail figures representative of normal operations, we use a pre-disruption timetable for Brisbane and will switch back once normal services resume.

Section 5

Reforms & capacity

Reform unlock (net new homes): The headline figure on the reforms page: the net new homes a reform would legalise on top of today’s rules. It’s scored lot by lot—each lot is capped by the largest building its size and street frontage can physically take—and where several reforms overlap, the shared land is counted once so homes aren’t double-counted. It measures what becomes legal to build, not what will be built: in practice only a small share of newly legalised capacity is taken up each year (roughly 0.7–1% in comparable upzonings, drawn from California, Auckland and New York).
Zoned capacity: How many homes a city’s current zoning already allows—taken from the state government’s own published estimate where one exists. On the reforms page it’s the baseline a reform’s unlock is measured against, not a figure we model ourselves. Darwin is the exception: with no published estimate, it uses a proxy scaled from its current number of homes.
Potential dwellings increase: A reform’s unlock expressed as a share of what’s already there or already permitted—today’s homes (2021 census) plus the zoned-capacity baseline. “+150%” means the reform would legalise about one and a half times that combined base in net new homes.
Heritage and the capacity headline: Heritage-listed land is left out of every reform-unlock figure, because upzoning doesn’t remove a heritage listing—so it would be wrong to assume those lots get rebuilt. The unlock is scored on residential land with heritage excluded.

Section 6

Data versions

Snapshot: Every figure here is a dated, fixed copy of the data behind the site rather than a live feed. Planning schemes, property boundaries, heritage listings and transit timetables all change over time, so each release captures them as they stood when collected. A line at the bottom of every page shows which snapshot is currently in use.

Spotted a missing term?

Tell us

Send us a suggestion—additions take minutes.

Suggest an entry