Plot Ratio Controls
The Victorian Planning & Environmental Law Association (VPELA) recently held a seminar where the theme was 'To plot ratio or not to plot ratio?' Industry experts discussed the recent introduction of an interim plot ratio control in the Melbourne CBD (Schedule 10 of the Design and Development Overlay) that has taken the industry by surprise.
Mark Sheppard from David Lock Associates presented 'Plot Ratio Controls: amenity, infrastructure and other consequences’. His presentation examined whether the new plot ratio control is justified, and looked at other consequences that may arise from it.
The reasons for the plot ratio control put forward by the Department of Planning relate to internal amenity, equitable development opportunity (the internal amenity of future adjacent development), public realm amenity and character, and infrastructure capacity.
In order to test whether the plot ratio control results in improved amenity and equitable development, Mark investigated the range of different building forms possible on typical small and large properties in the CBD using a 24:1 plot ratio. This demonstrated that it is possible to have both good and bad amenity and equitable development outcomes whilst still complying with the plot ratio control. In other words, there isn’t a direct relationship between density and amenity. The plot ratio control does not ensure good amenity or equitable development and, therefore, cannot be justified on these grounds.
This is not to say that controls to ensure good amenity and equitable development opportunities are not required. But a plot ratio control is not the way to achieve these outcomes.
Increased density generates increased demand for open space and other community facilities (and utility services). The plot ratio of a development is, therefore, a useful way to measure the need for additional infrastructure. As a result, it may be a useful mechanism for determining development contributions.
However, there do not appear to be any ultimate infrastructure capacity constraints. In terms of transport capacity, it could not be said that Melbourne's wide streets are at their limit. The footpaths are not full, and there is far more movement capacity to be released by reallocating road space from cars to pedestrians and trams.
Therefore, the plot ratio limit is not justified by infrastructure capacity either.
Mark identified a number of other potential consequences of the plot ratio control that might provide a justification for it, and should at least be considered in the refinement of the control.
Certainty - Plot ratio controls provide greater certainty in relation to land value, which may reduce speculation and adversarial planning permit processes. However, this certainty is not always justified, because not all sites can achieve the maximum plot ratio. Further, a plot ratio control does not provide certainty to the community about building form or amenity.
Transferable development rights - The ability to sell the floor area entitlement of a property may encourage the preservation of heritage and characterful buildings. However, this may also lead to excessive height on the property for which the floor area is purchased.
Basement parking and services - Because the plot ratio is only calculated on above-ground floor area, it may encourage the location of parking and services at basement level where ground conditions allow, resulting in better street activation.
More diverse built form - When used without height limits, plot ratio controls foster a more diverse built form because there are so many different building forms that can be adopted on a given property. However, Melbourne already has a diverse built form pattern owing to the highly varied site characteristics. A uniform plot ratio control also runs counter to the idea of shaping the built form pattern to create a more legible place.
Plot ratio controls are not the best way to ensure good internal amenity, equitable development or good public realm amenity. Nor is one necessary to manage demand for street space in Melbourne.
Where a plot ratio measure and/or control could be useful is:
- to measure the need for additional infrastructure (and form part of a development contribution mechanism)
- to provide greater certainty in relation to the value of land
- to incentivise the preservation of heritage/ characterful buildings
- to discourage above-ground parking and services.
To view Mark’s presentation please click here.