Building on the side boundary (zero lot line)
13 The three dwellings are built to the side boundary with two-storey high walls. In my opinion, this is the worst feature of the proposal, and it is a necessary consequence of the 5m-width. There is, of course, no problem with the party walls that straddle the boundaries within the development as these have impact only on each other. The problem occurs where the dwellings at the eastern and western end are built on the boundary and thus impose an impact on Nos 48 and 56, both of which have set back from their own side of the common boundary, with the exception of the single-storey garage on No 48.
14 Detached dwellings in Sydney are usually built with a setback of 900mm or more from the side boundary. The major exception to this is the traditional terrace house, most examples of which are in the inner suburbs. Terrace houses are usually separated by party walls, which straddle the common boundary.
15 Building to side boundaries has been re-introduced into modern town planning with townhouse and villa home development, as well as with a form of housing that is usually referred to as zero lot line. In zero lot line housing one side wall (usually without windows) is built on the boundary while the setback on the other boundary is increased. The advantage is that instead of two narrow setbacks, each dwelling enjoys one spacious and therefore more useable setback.
16 For the above examples to provide good amenity, they require the coordinated development of a group of dwellings. Where the wall of a dwelling is built on the side boundary, the adjoining dwelling should either be built on the boundary (as in town houses and villa homes) or alternatively it should be built a sufficient distance from the boundary to provide a useable outdoor area. The question arises whether building on the side boundary is appropriate at the ends of such developments, where the adjoining site is under another owner's control. In most such cases, building on the boundary is not appropriate.