frequently asked question
What's the problem with building setbacks?
Building setbacks, whilst often argued for with good intentions, have a large number of negative ramifications that make our housing outcomes worse.
The issues with setbacks fall into two main categories: increasing building complexities and decreasing amenities.
To put it simply, buildings with a traditional “boxy” shape are just simpler (and cheaper) to build and maintain whilst more complex shapes do the exact opposite. The more setbacks required the more complexity goes to the building foundations, waterproofing, service/infrastructure, etc. All these factors add up and not only just significantly increase the construction costs, they make the long term performance of buildings likely to be worse.
This is backed up by research from the City of Toronto Planning and Development Department, who found that the elimination of setbacks would lead to "the greatest reductions in both embodied and operational carbon and have the additional benefit of simplified structures and envelopes - a move that would allow a wider range of structural materials to be employed and greater energy efficiency in envelope systems".
There is research to suggest that setbacks—via the extension of internal floor slabs—can cause buildings to lose thermal efficiency due to thermal bypassing. This is in addition to them being less thermally efficient from the onset due to having a larger surface area to their volume, compared with buildings without setbacks. These two factors combined means that setbacks cost more and produce more emissions due to their much higher energy requirements. These increased amounts of points of potential water ingress also create more unnecessary risk for timber rot and for the growth of mould.
Whilst the rationale for setbacks is often based around improving the amenity of the streetscape (i.e. how tall the building appears on the street level) this often comes at the cost of amenity of the residents of the building and relies on the assumption streetscapes are inherently better when the building height is obscured.
The nature of setbacks means that the bottom levels of the building needs to be long enough to meet the required setback requirements of the upper levels. However, this means that the housing on lowest levels are built deep into the building with more limited access to light and airflow when there are other buildings surrounding the rear. This issue is one exacerbated by setbacks and could be solved by removing setbacks and allowing for a thinner rectangular building with plenty of rear open space.
On the upper levels, the long setbacks completely block residents' views of the streetscape, cutting off their connection with the street whilst removing the safety benefits of “passive surveillance”.
Moreover, setback requirements force developments to have reduced floor area ratio (FAR)—otherwise known as ‘density’. In practice this means the number of homes a project can supply is either reduced or the apartment sizes/number of bedrooms are reduced. The former has implications to housing affordability whilst the latter limits the type of housing diversity that can be delivered by these projects.
Many advocates for the current setback regime argue that they play a vital role in preventing urban canyoning or wind tunnelling—which are fair concerns and worthy of addressing through policy and planning tools. However, the height buildings need to be for these concerns to be valid is significantly disconnected from when setbacks requirements kick in. For example with wind tunnelling, buildings need to be around 20 stories or 76 metres tall before it becomes an issue whilst setback requirements can start as low as 2 storeys or 8 metres!
Another notable argument for setbacks surrounds overshadowing and sunlight. The current controls operate under the assumed supremacy of goals to minimise the amount of shadow cast and maximise the amount of sunlight. However, this assumption is falling under greater scrutiny in a world where heat is seen as a great threat to urban public health. Is minimising shade in urban spaces worth prioritising above all other amenity concerns? In Melbourne—a city famous for its cloudy weather—is overshadowing such a major concern for a majority of the year if the sunlight is mostly diffused? These are questions that have yet to be explored thoroughly in Melbourne.
When considering the number of trade offs associated with mandating setbacks, it’s hard to see why they’re worth it for the limited scope, and questionable nature, of the perceived benefits. Setback controls in Melbourne are in desperate need of a rethink.