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New report: Unintended consequences of mandatory height controls excludes timber

Home » New report: Unintended consequences of mandatory height controls excludes timber

For the property development industry, the benefits of using timber building systems can lower costs and produce faster build times. For sustainability-driven local governments, it can reduce greenhouse gas emissions and increase carbon storage. So why isn’t it being encouraged?

A new report has found that mandatory height controls in the Victorian planning system have unintentionally penalised timber building systems, favouring the use of expensive, energy-intensive concrete and steel alternatives.

People familiar with the property sector will have noticed the growing popularity and visibility of timber in both the international and Australian markets. From innovative new mass timber systems such as cross laminated timber (CLT) to traditional stick framing, timber as a material is undergoing something of a renaissance, particularly in mid-rise developments (although it should be noted it’s often the much taller timber projects that seize the headlines).

A new report, Timber Construction and Building Height Planning Controls – The unintended consequences of the Planning System by Melbourne town planners, urban designers and landscape architects Tract, investigates the role of the Victorian planning system in determining the choice of materials used for construction projects. In the report, Tract conclude that predominant use of ‘metres’ rather than storeys in planning requirements is likely to constrain the uptake of timber in building construction. This is due to the additional height often required for the floor/ceiling system and the reluctance of developers to challenge the planning process.

“An inflexible height limit, in some cases, means that a project will be designed in concrete because it becomes one storey less in timber and therefore less viable for the developer,” said Robert Pradolin, former General Manger for Frasers Property Australia and now a strategic advisor in the affordable housing space. “The typical driver for a developer is yield. A timber structural solution generally requires a greater floor thickness. This increases the overall height of the building and, in some cases, may exceed the existing height controls. The loss of a floor due to using timber can make it unviable for the developer and therefore the other benefits of using timber, including affordability and sustainability, are lost to the broader community.”

The advantages of timber, from the Tract report, include; it’s a natural material with low embodied energy that also stores carbon; it can be easily recycled; it has excellent insulation, thermal and fire performance; it is durable and easy to maintain; it offers design flexibility and workability while also potentially tapping into the benefits of biophilic (or ‘nature-centric’) design for the building’s occupants.

Timber building systems also deliver benefits during the construction phase of a project. Pradolin says “Typically, when compared to concrete, much of the structure is premanufactured offsite. This results in improved OH&S, better quality control as manufacturing is done under cover and in controlled conditions and increased neighbourhood amenity as fewer truck movements are required, significantly reducing the impact to local residents during construction. Timber structures are generally one third lighter than concrete and have lower foundation costs. From the financing aspect, using timber results in a faster build time which reduces the financing costs. When considering all these advantages, I believe the case for developers to use timber is very compelling”.

Timber however, suffers from a problem not anticipated by those who first stipulated mandatory height controls; a deeper floor system. As the Tract report explains:

“Because timber has different strength and weight properties to concrete, the depth of the timber floor system will generally need to be deeper than those required for a concrete floor. Therefore, the actual overall height of timber buildings will need to be slightly higher to accommodate the additional depth requirements for buildings with the same number of stories. 

A comparison of the floor systems for concrete and timber construction techniques indicate a variation of the floor system depth of approximately 250mm for each floor… for a 5 storey building, a timber building will be typically 8% higher than a concrete building.”

According to Tract, under the Victorian Planning Provisions (VPP), the local authority does not have the discretion to approve an increase in height to promote the use of a more sustainable material like timber, despite wanting to encourage its use and consequent benefits. This puts timber at a competitive disadvantage.

A situation further compromised when a planning permit has already been granted for a concrete building and the developer would like to consider converting the building to timber. Any height increase (even with the same number of floors), triggers a permit amendment process. These are typically subject to notice (public advertising) and review provisions, which can be both costly and time consuming. This acts as a further disincentive to change the material to timber.

“Most developers will not go through another long, difficult and problematic amendment process just to change from concrete to timber. They will always take the easiest route and stay with concrete” Pradolin says.

The comprehensive report also includes; examples of multi-storey timber projects, case studies of planning permission processes and an analysis of the variations in planning requirements of Australian States and a comparison of several Melbourne councils.

Tract conclude that “It is clear that changes to planning schemes are needed to: Allow for timber constructed buildings to marginally exceed height limits, and provide a fast tracked permit amendment process to specifically allow an approval process by the responsible authority if it is purely a material substitution. This would allow much more timely conversion of concrete construction to timber where there is an existing permit.”

They also recommend changes at the State level through the VPP, as the alternative, individual changes to planning schemes at the local Council level are likely to be time consuming and ineffective.

But as with all planning changes, it is important that the community and local government is educated about these “unintended consequences” so they can discuss, debate and resolve what they should do, if anything, as a community.

Ric Sinclair, Managing Director of Forest and Wood Products Australia Ltd (FWPA) the industry organisation that resources WoodSolutions said “We believe local governments need to be aware of these unintended consequences and discuss this with their constituency. We know that climate change is real, we know we need to become more sustainable, and we know that timber should at least be considered as an option, especially given its sustainability benefits. We just want to let the public know and start the discussion”.

With his many years in the development industry, Pradolin knows that the government and the community need to be consulted.

“Ultimately, any changes will come down to what the local government, and its community, want to encourage. The requirements to be more sustainable in our built form will only increase with time. We have a building material that captures carbon, is cheaper to build and is sustainably grown. It creates real value for all stakeholders. It’s probably the ultimate renewable. It seems everybody wins using timber.”  

Timber Construction and Building Height Planning Controls – The unintended consequences of the Planning System

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Timber Construction and Building Height Planning Controls report.

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