The first question on the property developer's mind is house and lot size then followed by "how many bedrooms?"

The developer can then estimate the cost to build the project, the selling price, and the profit they might make.

The size of the house on the block- be it a single dwelling, a dual occupancy or townhouse development- will rely on the Council’s planning scheme ( the “rules”).

Calculate the size of each dwelling from the zoning, the schedule to the zoning, any other planning scheme overlays, the garden area requirements, the site coverage allowed and other factors which play a role on the size of the dwelling.

Those factors could include the neighbourhood character to be met, Councils strategic plan for the area, vegetation on the land, on the nature strip and on abutting property to name a few.

The key items to consider for a fast appraisal of building size are:

The Site coverage

Building Setbacks

Garden Area

Permeability

Landscape

Open Space

Parking

Driveways in Strata lot subdivision

Roads in Torrens title subdivision

Strata lots

This are how the block of land is subdivided in townhouse, dual occupancy, industrial or apartment projects. In townhouses the driveways are maintained and owned and shared by each unit owner and known as common area (like a lobby or lift in an apartment block). The townhouse owners walk up the narrower driveway to leave the garbage bins or collect mail from a bank of letterboxes located at the front boundary.

Torrens title

In these lots there is a wider public road in front of the lot which is owned and maintained by council. The postie drops the mail in the letter box at front, the garbage trucks collect the bins left on the kerbside, there is a footpath and nature strip with streetlights.

Site coverage

Councils will generally allow (in theory) 60% of the land to be developed by the building footprint.

That means if your land is 1000sqm, the building’s ground floor including garage and porch can occupy 600sqm.

However, by the time you cover the other planning requirements, the 60% number diminishes in property developments for townhouse or dual occupancy.

In some zonings that 60% number reduces to 50% or even as low as 40% and 30%.

Setbacks

Each dwelling must be setback from the front (street) boundary, side, and rear boundaries as per Rescode or Clause 55 of the Planning Scheme.

The front building line should be the average of the buildings on either side or as specified in the Schedule to the Zoning.

Setbacks can reduce building footprints!

Garden Area

This new requirement kills the development size.

The Garden area depends on the land size.

In typical developments on land over 650sqm, 35% of the land must be dedicated to the Garden Area.

In property developments, we have found this factor itself can reduce the number of townhouses. In one project it reduced the units from five down to four townhouses to satisfy the Garden Area requirement! In another the number of bedrooms and size of each townhouse shrank significantly.

Garden Area plays a key role in deciding the size of the house for a property developer.

Permeability

This relates to collection of rainwater. Hard surfaces like driveways collect stormwater and divert it to the stormwater drainage system which are mostly in poor condition or were not designed for urban growth.

Permeable surfaces allow the stormwater to soak through the ground instead of it being collected and diverted to the drains.

Councils specify the amount of land which cannot contain hard surfaces like driveways.

Landscape

Some Councils have specific landscape requirements. Some go as far as specifying how many new trees must be planted and how much land must be allocated to each new tree on a block ripe for property development or subdivision!

Landscape is usually required in the front and rear of the block being subdivided and along the sides of the driveways or roads in the subdivision.

Open Space

This is a standard requirement for all property developments.

They fall under two types.

The open space per dwelling and the secluded open space per dwelling.

In its simplest form you can think of the secluded open space as being a private courtyard for each house where it is fenced for privacy and security.

The size of it can vary from 20 sqm. in a Growth Zone, 25% in a General Residential Zone and up to 60sqm per dwelling with minimum dimensions!

They should ideally face north and be located at the side or behind each townhouse and not in the front yard.

The open space is all the unbuilt space per dwelling including the secluded open space. This size can vary between 40sqm and 80sqm per house!

This planning requirement also impacts the size of each dwelling.

In some Zonings the secluded open space can be a balcony or roof garden accessed from a living area.

Parking

Each house must be provided with one or two car spaces.

Car spaces can be open to sky or under cover like carports and garages.

Each of these spaces will occupy a specific size.

A two bedroom house requires one space which can be open to sky but a 3 or more bedrooms requires two spaces of which one must be under cover.

Visitor parking is required for property development containing 5 or more townhouses.

Parking consumes a chunk of the developable land.

Driveway

For the typical property development in an established suburb, driveways are provided for dual occupancy or town house projects.

They need to be a specific width with 3m width being the lowest.

In more intense developments the width could increase to 6.4m to allow cars to turn within the developments and not reverse out. Reversing out the vehicle can be dangerous for pedestrians and animals.

In large subdivisions, the driveway is replaced by a wide public road with footpaths, kerbs, and nature strips on either side. These roads can occupy 18m in width chewing up valuable land.

Swarup Dutta, AuArchitecture’s Founder, is a Registered Planner and affiliated with the Australian Institute of Architects, Planning Institute of Australia and Victorian Planning and Environmental Law Association. While consulting to real estate developers and Architects he managed over 250 planning permits in Victoria.