In the current debate about apartment design standards, the issue of how to determine height is one that has yet to be be fully canvassed.

During recent submissions on proposed amendments to the planning scheme of a Victorian local council, arguments were presented as to whether its Design Development Overlay (DDO) should express building heights in metres rather than storeys. On one side, expert witnesses preferred heights in storeys to allow some flexibility and encourage the amenity of more generous floor to ceiling heights and clever apartment design.

Opposing this view, the local action group argued that maximum building heights ought to be prescriptively in metres and not storeys. As we know, height is always a touchy point for local residents.

Council also preferred prescriptive measures – metres rather than storeys – as this is simpler to administer and gives less opportunity for applicants to argue the toss.

In short, designers want flexibility, residents want stability and consistency and councils want certainty. Nothing wrong with aspirations for certainty and consistency – if only real life was that simple!

Councils have two types of height control at their disposal; mandatory prescriptive metrics and discretionary controls, which require a planning permit.

Mandatory controls may be specified in a DDO and may nominate an absolute height that cannot be varied, except by an amendment to the planning scheme. A discretionary control, whereby a planning permit is required for development, will often specify building height as a consideration but allows Council to assess impacts of taller buildings via the planning permit process.

Planning policy is ideally couched in terms designed to give guidance but not be so narrow as to discourage or quash creative architectural solutions. A performance-based development control mechanism utilises the planning permit process to make planning decisions and to reduce the need for planning scheme amendments. It works more flexibly than mandatory controls and allows greater innovation and design-led thinking. A prescriptive approach to height is at odds with the stated objectives set out by most councils. These instruments are commonly about interpretive and sometimes subjective values such as context, quality of built form, heritage and sustainability outcomes and the like.

It is understandable that authorities prefer prescriptive measures such as the use of metres rather than storeys as their height controls. A prescriptive requirement is simpler to administer. It may be better understood within the general community and cause less argument. A quantifiable measure engenders a degree of certainty and consistency in the planning process. This is fine if our goal is cookie-cutter design. However, I suggest that this is neither the basis for good policy, nor can it encourage good urban design outcomes.

Consistent pressure is applied on state governments to accept mandatory height controls, especially in areas where density opportunities call for higher buildings. Policy discussion on height at government level seem to start around specification in terms of number of storeys, but then somehow ‘morphs’ into specific metric controls when policy papers are issued. This wouldn’t be so bad if there were at least some consistency in height planning decisions. Unfortunately as the following Victorian examples demonstrate, this is not the case:

• Whitehouse Planning Scheme: residential storeys may typically be three metres between floor levels
• Boroondara DDO Amendment C139: floor to ceiling height of four metres for the ground level, with 3.5 metres for subsequent levels
• Melbourne City Council Design and Development Overlay Amendment C196: minimum ground floor to floor height of four metres at ground floor and a minimum floor to floor height of 3.2 metres in levels above the ground floor.

Disturbingly, amongst the various criteria used by authorities to determine planning height, structure seems to be poorly understood and consistently taken for granted. As the examples above demonstrate, planners don’t seem to grasp the practical realities of building. If they did, there would not be such a wide discrepancy in height allowances.

Best practice in this area currently comes from those authorities who realise that amenity and structure are two entirely different considerations and need to be dealt with separately. The recent NSW Residential Flat Design Guide (SEPP 65) for example has considered its height guidance as two components; minimum amenity standards for floor to ceiling height and the interstitial space comprising floor structure:

A floor to ceiling height of 2.7 metres achieves the floor to floor height of 3.1 metres, which is the minimum to allow for finishes and construction tolerance. Floor to floor heights greater than 3.15 metres allows for acoustic insulation and is considered better practice and encouraged where possible.

Floor to ceiling standards are fairly consistently agreed upon and evidence based, with 2.7 metres being widely adopted as the minimum acceptable height for comfortable habitable areas and 2.4 metres for non-habitable areas.

SEPP 65 then recommends the allowance of a set amount for structure and services. This component should ideally allow for the various structural frame options available and provide for ancillary sound and fire standards compliance measures and services. As these measures are specified in the BCA, it seems to me that setting depth standards for this interstitial zone is more appropriately the province of the BCA, rather than by ad hoc nominations in individual planning schemes.

With the newly announced BCA height standards for timber-framed construction, the interstitial space required for structure and services requires review and standardisation to ensure all current structural systems are catered for. It is certainly about time for the current vagaries and inconsistencies of building height standards to be nationally rationalised from planning laws, such that architects and engineers can work with greater certainty and clarity when designing building envelopes.