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Special Article - A View of Housing Density in Perth
RESIDENTIAL BUILDING APPROVALS, Perth Statistical Division
To compile an alternative broad measure of medium density housing, house approvals identified from the analysis as constituting grouped dwellings were combined with semi-detached-type dwelling approvals to derive the category "clustered dwellings". The figure below depicts this process and shows the number of clustered dwellings approved in each of the reference years as well as the contributions made to this category by grouped dwelling and semi-detached-type dwelling developments.
Of the 42,708 dwelling units approved from 1998-99 to 2000-01, 80% (or 34,067) were houses. Analysis of these house approvals established that:
Clustered dwelling developments (grouped dwelling and semi-detached-type dwelling approvals) over the three study years totalled 9,696. Grouped dwellings comprised half of the clustered dwellings category, their number being slightly higher than semi-detached-type dwellings in two of the three years.
As a result of applying the methodology to new residential approvals over the three years:
Flats, units and apartments make up the remainder of approvals.
CLUSTERED DWELLINGS - DENSITY AND GROSS SITE AREA (GSA)
The ability to identify clustered dwelling approvals provides the opportunity to examine the number of dwellings associated with each approval (a broad measure of medium density housing) as well as variations in the average gross site area per dwelling in clustered dwelling developments.
As shown in the following table, the highest proportion of clustered dwellings comprised approvals of 5 or more dwelling units (41%) and 2 dwelling units (30%).
CLUSTERED DWELLINGS, Perth Statistical Division, 1998-99 to 2000-01
While the number of clustered dwellings provides a broad measure of medium density housing, a more informative view can be obtained by examining these developments in conjunction with their reported Gross Site Area or GSA (i.e. the site area or size of the block, in square metres, on which the approved building work is being carried out). The results are shown below.
There were known deficiencies in the quality of GSA data as supplied by local government authorities - GSA is a mandatory item which is not well reported by some councils. Nevertheless, these results serve as a general indication of variations in housing density within the clustered dwellings category.
CLUSTERED DWELLING APPROVALS, Average GSA per dwelling
2 CLUSTERED DWELLINGS
3 CLUSTERED DWELLINGS
4 CLUSTERED DWELLINGS
5 OR MORE CLUSTERED DWELLINGS
The average GSA per dwelling decreased as the number of dwellings within each clustered dwelling development type increased. The largest proportion of dwellings for various development types fell in the following average GSA per dwelling range:
By comparison, the largest proportion of single house approvals (31%) had an average GSA in the range 600 to 699 square metres as depicted in the figure below.
SINGLE HOUSE APPROVALS, Average GSA Per Dwelling
CLUSTERED DWELLINGS - GEOGRAPHICAL DISTRIBUTION
The degree to which clustered dwelling developments are occurring across the Perth metropolitan area is depicted in the following map.
In 22% of Perth suburbs, clustered dwelling approvals comprised 48% or more of total dwellings approved over the reference period. In another 25% of suburbs, the proportion ranged between 21% and 48%.
There were four notable suburb groups within which clustered dwellings comprised 48% or more of new dwelling approvals:
All are established residential areas, suggesting that there is an increase in urban infill occurring across the Perth metropolitan area.
CLUSTERED DWELLING APPROVALS AS A PROPORTION OF TOTAL DWELLING APPROVALS
STUDY METHODOLOGY AND DEFINITIONS
Functional Classification of Buildings - Residential Component
The FCB is used by ABS to code buildings according to the intended main purpose of the building. For residential buildings, the codes and their descriptions are:
FUNCTIONAL CLASSIFICATION OF BUILDINGS, Residential component
From 1 July 2001, the ABS commenced coding building approvals using a revised FCB. The residential sector of the classification has remained unchanged. More details are provided in the August issue of Building Approvals, Australia (Cat. no. 8731.0).
Identifying Multiple Dwelling Developments
Building approvals classified to a house (i.e. FCB code in the range 011 to 019) and consisting of 2 or more dwelling units (reported Number of Dwellings greater than 1) were separately identified as grouped dwellings.
Other multiple dwelling developments
Other types of multiple dwelling developments appeared to be represented in the approvals data but could not be conclusively identified. Examples include:
General Description - 3 dwellings: 2 attached and 1 detached
ABS FCB - 1 house: 2 semi-detached-type dwellings
Study description - 2 approvals: 1 house and 2 clustered dwellings
Definitions of Building Categories Devised for this Study
The following building type categories devised for this study are based on concepts or terms generally accepted in the Western Australian user community.
A detached building primarily used for long term residential purposes and consisting of one dwelling unit on a single parcel of land. This is essentially the ABS definition of a house (FCB codes 011 to 019) qualified to indicate the approval/construction of only one house on a parcel of land.
Formed when two or more detached dwellings (houses) are grouped together as a single approval and constructed on a single parcel of land (as depicted in the figure below). These development types are an increasingly popular alternative method of construction to duplex- and triplex-type housing (FCB codes 021 and 022). Survey strata schemes are often used with these developments as an alternative means of lot subdivision to provide for an exclusive area to be occupied by, and used by, each dwelling. This analysis was able to identify such developments which correspond with the WA housing industry's description of grouped dwellings.
General Description - 3 detached dwellings
ABS FCB - 3 houses
Study description - 3 clustered/grouped dwellings
Comprise grouped dwelling developments (as defined above) and semi-detached-type developments (FCB codes 021 and 022). This category represents a broad indication of medium density dwelling development. It is an extension of the currently available indicator represented by semi-detached-type developments. The figure included under the heading "Number of Dwellings" above depicts the process of deriving clustered dwelling developments.
The above analysis has expanded the range of ABS measures of housing density. Building approvals data have been used to identify and reclassify grouped dwellings from low to medium density.
For clustered dwellings, the results illustrate the trend toward a smaller average gross site area per dwelling as the number of dwellings in such developments increases. The results also point to an increase in urban infill occurring across the Perth metropolitan area, particularly in the more established residential suburbs.
For further information on this analysis, please contact Robin Dalby on Perth (08) 9360 5254 or email: firstname.lastname@example.org. For general information on Building Approvals, including requests for data, please contact Andrea Woods on Adelaide (08) 8237 7350.
Building Approvals, Western Australia (ABS Cat. no. 8731.5)
Building Approvals, Australia (ABS Cat. no. 8731.0)
Australian Standard Geographical Classification (ASGC) (ABS Cat. no. 1216.0)
ABS Functional Classification of Buildings
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