Is a duplex the same as a semi-detached house?

Often people use the words for the same thing: two homes sharing one wall. The ABS counts both as semi-detached, row or terrace homes. The difference to check is whether the two halves sit on one lot or two. A NSW dual occupancy is two dwellings on one lot, so separate titles require subdivision.

Can you buy just one half of a duplex?

Only if that half has its own title, either a Torrens lot or a strata lot. A dual occupancy starts out as two dwellings on a single lot. A title search shows whether subdivision has been registered, and a conveyancer can explain what the title means for repairs, insurance and rules.

Do duplex owners pay body corporate fees?

It depends on the title. A Torrens duplex with no shared property has no scheme and no levies. A strata duplex has a scheme, and levies cover its insurance and common property costs. In Victoria, an owners corporation arises where the plan creates common property, so the plan is worth reading.

Do I need to insure a duplex myself?

Where there is no scheme, the owner arranges building insurance. Where there is one, Moneysmart says the body corporate may insure the building, and you still need contents cover for your belongings. Read the policy wording for what it covers.

Is a duplex a townhouse?

Not in NSW planning terms, where two dwellings on a lot is a dual occupancy and three or more is multi dwelling housing. In ordinary speech the words overlap, and townhouses are often in groups of three or more. Check the title and the plan rather than relying on the label.

What is the difference between a townhouse and a duplex?

A duplex is generally two homes on one block that share a wall, while a townhouse is usually one of a row or group of attached homes. "Duplex" is an everyday word rather than a planning term: NSW planning documents call the arrangement a dual occupancy, defined as two dwellings on one lot of land. For a buyer, the difference that matters most is title, because it decides who maintains what and whether any levies apply. The planning definitions below were checked in October 2026.

Checked October 2026. Rules, rates and prices change, so confirm anything that matters with the source linked below.

What the terms mean in planning rules

NSW's planning department defines a dual occupancy (attached) as two attached dwellings on one lot of land, and a dual occupancy (detached) as two detached dwellings on one lot. Neither includes a secondary dwelling such as a granny flat. NSW's low-rise design guide describes multi dwelling housing as three or more dwellings, attached or detached, on one lot. On those definitions the split is a head count: two dwellings is a dual occupancy, three or more is multi dwelling housing, which is where most townhouse groups sit. The NSW Planning Portal's BASIX page, by contrast, lists dual occupancy, villa units and attached townhouses together under one multi dwelling heading, so the grouping depends on the document.

Other states use different words. Western Australia's Residential Design Codes use "grouped dwelling" for a group of two or more dwellings on a lot where no dwelling sits above another, so a two-home duplex is a small grouped dwelling there. Victoria's Townhouse and Low-Rise Code applies to "two or more dwellings on a lot", again without a separate duplex category.

For statistics, the ABS puts both in the same bucket if they have their own private grounds, nothing above or below, and are attached to a neighbour: "semi-detached, row or terrace house, townhouse". The line between the two is a marketing and planning one, not a statistical one.

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Title is the real difference

A dual occupancy starts out as two dwellings on one lot. To own one of them separately, the lot has to be divided, either into two Torrens lots or into strata lots. Councils handle this in different ways. Sutherland Shire Council lists both Torrens and strata subdivision as options for a dual occupancy. Randwick Council's page sets minimum lot sizes for subdivision, such as 275 square metres per lot in the R2 zone outside heritage areas and 400 square metres inside them. Those figures belong to those councils and zones, not to NSW as a whole.

	Torrens duplex	Strata duplex	Townhouse in a group
What you own	Your own lot and the building on it	A lot, plus a share of common property	Either, depending on the scheme
Shared wall	The boundary may run on or through the wall	Boundary set by the strata plan	Same questions apply
Scheme levies	None unless an association exists	Yes, set by the scheme	Yes if strata or community
Insurance	Owner arranges building cover	Scheme usually insures the building	Depends on title

The wall question varies by state and by plan. In Queensland, under a standard format plan the boundary usually runs down the centre of a shared structural wall, and the Queensland Government says the body corporate generally has no responsibility for it because no common property is involved. In Victoria, an owners corporation is created when a plan of subdivision creates common property, so a two-lot subdivision with none may have no owners corporation. The title search and plan show what applies. The guide to Torrens and strata title for townhouses explains the two systems.

Costs, insurance and repairs

Where no scheme exists, you are responsible for the building and its upkeep. Moneysmart says building insurance covers the structure and fixtures, and that you should check with the body corporate to see whether it insures the building. Where a scheme exists, ask for its budget, insurance details and by-laws, and see the guide to townhouse body corporate fees.

A shared wall brings shared risk. A fire in one half or a structural problem with the wall affects the other, which is why it is worth understanding party walls and shared walls before you sign. The National Construction Code's Housing Provisions (2022 edition) set rules for separating walls between attached Class 1 buildings, which cover both duplexes and townhouses. One requirement is a fire-resistance level of 60/60/60 or masonry at least 90 millimetres thick.

If the duplex is new or planned

Approval pathways differ by council. Randwick says new dual occupancies need a development application and a construction certificate. Sutherland says a complying development certificate is available in its R2 and R3 zones through an accredited certifier, with a development application needed elsewhere.

NSW also introduced a Low and Mid-Rise Housing Policy from 28 February 2025, which brings new controls for dual occupancies, terraces and townhouses near town centres and stations. It excludes heritage items, among other areas. Rules for any particular lot depend on its zone and council, so the council's planning team is the place to confirm.

Common questions

Is a duplex the same as a semi-detached house?: Often people use the words for the same thing: two homes sharing one wall. The ABS counts both as semi-detached, row or terrace homes. The difference to check is whether the two halves sit on one lot or two. A NSW dual occupancy is two dwellings on one lot, so separate titles require subdivision.
Can you buy just one half of a duplex?: Only if that half has its own title, either a Torrens lot or a strata lot. A dual occupancy starts out as two dwellings on a single lot. A title search shows whether subdivision has been registered, and a conveyancer can explain what the title means for repairs, insurance and rules.
Do duplex owners pay body corporate fees?: It depends on the title. A Torrens duplex with no shared property has no scheme and no levies. A strata duplex has a scheme, and levies cover its insurance and common property costs. In Victoria, an owners corporation arises where the plan creates common property, so the plan is worth reading.
Do I need to insure a duplex myself?: Where there is no scheme, the owner arranges building insurance. Where there is one, Moneysmart says the body corporate may insure the building, and you still need contents cover for your belongings. Read the policy wording for what it covers.
Is a duplex a townhouse?: Not in NSW planning terms, where two dwellings on a lot is a dual occupancy and three or more is multi dwelling housing. In ordinary speech the words overlap, and townhouses are often in groups of three or more. Check the title and the plan rather than relying on the label.

Keep reading

Sources

This is general information, not financial, tax or legal advice. Get advice that suits your situation before you buy.