Dwelling structure (STRD)

Latest release
Census of Population and Housing: Census dictionary
Reference period


This variable records the structure of private dwellings.


Private dwellings


11Separate house
21Semi-detached, row or terrace house, townhouse etc. with one storey
22Semi-detached, row or terrace house, townhouse etc. with two or more storeys
31Flat or apartment in a one or two storey block
32Flat or apartment in a three storey block
33Flat or apartment in a four to eight storey block
34Flat or apartment in a nine or more storey block
35Flat or apartment attached to a house
92Cabin, houseboat
93Improvised home, tent, sleepers out
94House or flat attached to a shop, office, etc.
&&Not stated
@@Not applicable

Number of categories:  14

Not applicable (@@) category comprises:

  • Non-private dwellings
  • Migratory, off-shore and shipping SA1

Category definitions

Question(s) from the Census form

This variable is not collected from a question on the Census form.

How this variable is created

Initially, this data is sourced from the ABS Address Register. For more details, refer to the ABS Address Register, Users' Guide.

In some cases the Dwelling structure is updated after information is returned from ABS field officers during their visits to dwellings.

New dwellings added by Census staff can have their Dwelling structure added by the field officer or imputed from the surrounding dwellings during processing.

Depending on Dwelling structure type and the method by which the Address Register is updated, the private dwelling’s structure can be derived from the Address Register (with Building Approvals data also assisting in some cases) or information obtained by Census field officers. Structure for Non-private dwellings (NPDs) are set to ‘not applicable’.

Certain types of dwelling structures, such as 'Improvised homes, tent, sleepers-out' are given particular attention during data processing to quality assure the homeless population.

History and changes

Some information on the structure of Private dwellings has been collected for all censuses since 1911, though the specific types of classification used have varied significantly.

Cabins and Houseboats

Prior to the 1986 Census, occupied craft in marinas were treated as Non-private dwellings, however occupied houseboats and occupied small boats are now treated as Occupied private dwellings.

Collection methods before 2016

From 1976 to 2011, the information on Dwelling structure was collected by Census Field Officers in the Collector Record Book at the time the Census forms were delivered instead of being on the Census form.

In 2016 there was a change in the way the data was collected. It was initially recorded by ABS Address Canvassing Officers in the lead up to the Census, as part of establishing the Address Register as a mail-out frame for designated areas (93% of Australian addresses). In areas enumerated using the traditional approach of delivering forms, the information was collected by ABS Field Officers during the Census collection period. Location of private dwelling data was also updated as required by ABS Field Officers during the Census enumeration period. Dwellings in remote areas continue to have their structure collected solely by field officers.

In 2021, the Address Register is considered the main source of Dwelling location data, and real-world frame amendments are made when appropriate, by Field and Office staff.


For the 2016 Census, there was a change to one of the response categories for this variable. The previous category of 'Caravan, cabin or houseboat' was separated into two categories:

  • Caravan
  • Cabin, houseboat

In 2021, there has been further disaggregation of the flat/apartment categories to align with different building rules in place for buildings with a height greater than 25 metres and to meet increasing stakeholder demand for more data about high rise apartment buildings. The previous category ‘In a four or more storey block’ is separated into two categories:

  • In a four to eight storey block
  • In a nine or more storey block
Separate house and semi-detached definitions

For the 2021 Census, there is a change to the half a metre rule that had previously distinguished separate houses from semi-detached dwellings. The new definition is purely structural in which a separate house (constructed in the last 20 years) must be structurally independent, regardless of separation from adjacent dwellings. This change aligns with the way structure data is provided for the Building Approvals collection. See Housing variables for more information.

Missing dwelling structure

For the 2021 Census, addresses that do not have Dwelling structure recorded from observation or by the ABS address register can have the information populated by imputation.

Data use considerations

Data on Dwelling structure is used to monitor changes in housing characteristics, to help formulate housing policies and to review existing housing stock.

Minor inconsistencies in Dwelling structure counts may exist between censuses due to updated information on structure to the ABS Address Register and the subjective interpretation of structural definitions between individual Field Officers.

Although a review has been conducted to update Dwelling structure in light of changes to the half a metre rule for buildings constructed in the last 20 years, some older dwellings may still reflect the old definition.

Flats attached to houses are at a high risk of being missed as they are hard to identify, this is also the case for flats above shops.

The non-response rate for Dwelling structure (STRD) was 0.3% in 2021. This is a decrease from 0.5% in 2016.

Non-response for this variable was largely caused by previously unidentified dwellings being added to the census frame. This can occur when a member of the public submits their form online for an address that is not on the ABS Address Register or contacts the Census Inquiry Service. This results in dwelling structure not being recorded and is therefore left as a not stated response. 

Dwellings with no dwelling structure coded went through an imputation process to try and assign a structure code based on surrounding dwellings. Where a structure was unable to be assigned, the dwelling structure remained as not stated. 

Related variables and glossary terms

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