As many within the building sector throughout Australia would no doubt be aware, the 2016 edition of the National Construction Code (NCC) came into effect on May 1.
As with previous editions, the 2016 version of the Code contained a number of changes about which practitioners throughout the country need to be aware. Accordingly, an outline of the main points is presented below. For those seeking further detail, a complete list of amendments can be found in the back of each edition of Code.
Before describing the changes, a number of points regarding the context under which they are taking place should be acknowledged. First, as with previous years, the amendments are occurring as part of a broader agenda of reform on the part of the Australian Building Codes Board (ABCB) which is aimed at ensuring that the manner in which the Building Code of Australia (BCA) is being provided is conducive to delivering higher levels of productivity across the sector. This has led to a number of changes including the NCC being provided online at zero cost and a transition toward a three year amendment cycle for the Code which will see the next edition of the NCC being delivered in 2019 instead of next year as would have been the case under the previous twelve month amendment cycle.
These changes are important, ABCB boss Graham Moss says. Since making the BCA free online, the number of registered users of the document has jumped from around 12,000 to more than 80,000, he says. Citing a Centre for International Economics report, he adds that the aforementioned reform agenda was delivering cost savings to the Australian economy of around $1.1 billion per annum. Going forward, that report suggested that a further $1.1 billion can be saved – 70 percent of which would be achieved through greater use of performance solutions.
In addition, Moss says, there is an ongoing movement away from a prescriptive mindset when thinking about the Code toward one whereby the primary focus revolves around performance. Toward this end, the board is trying to emphasise the performance based mindset of the Code in 2016 along with the fact that whilst the Code does contain rules, the only requirements within the Code that are mandatory are in fact the performance based requirements. Whilst these can be achieved by a deemed to satisfy (DTS) solution (formerly referred to in previous NCC versions as a DTS provision), they can also be achieved by a performance solution (formerly known as an alternative solution).
Finally, whilst some of the changes indeed represent new additions to the Code, the large focus of a number of others revolves not so much around introducing new rules but rather clarifying areas of previous provisions contained within the Code where confusion had been experienced.
With that in mind, an outline of the amendments is as follows:
Application and General Provisions
In order to facilitate clearer understanding of the principles which underlie the core workings of the Code including its performance based nature, a number of the administrative and general provisions have been re-written and reworded (AO in Volume 1 and 1.0 in Volume 2). This is a ‘policy neutral’ change which does not alter the operation of the Code but rather clarifies how indeed it already operates: that is, that (a) the BCA is a performance based document in nature; (b) the only requirements contained in the Code which are mandatory are the performance based requirements; and (c) that these requirements can be met through either (i) deemed to satisfy solutions (formerly referred to as DTS provisions) or (ii) performance based solutions (formerly referred to as alternative solutions).
Mid-Rise Timber Buildings
By far and away the most talked about change revolves around the allowance of the use of timber in the construction of mid-rise hotels, apartment complexes and office towers under a DTS solution.
Previously, it has been possible to construct these types of buildings using timber, but this has only been able to be achieved via a performance solution as the maximum height allowable under a DTS solution for timber buildings was three storeys. The well-known ten-storey Forte apartment complex built by Lend Lease which used cross laminated timber (CLT) in Melbourne’s Docklands precinct, for instance, achieved compliance with the Code via a performance solution. Under the new Code, mid-rise timber buildings will be able to be built using a DTS solution and developers will no longer need to rely upon performance solutions.
At a technical level, whilst a number of clauses had to be added or amended in order for this to happen, the core of the new provisions are set out in the new C1.13 (Vol 1), which enables use of ‘fire protected timber’ for class 2, 3 and 5 buildings that reach no more than 25 meters (eight storeys) in effective height on the proviso that sprinkler systems are provided throughout, any insulation is non-combustible and cavity barriers are provided. Whilst the building can be a stand-alone building, the provision also allows for timber parts of buildings which can sit above or below other parts: for instance a timber apartment complex could be built on top of traditional concrete and steel construction used for retail space on lower floors within a mixed use setting.
A critical new concept in this area revolves around that of ‘fire protected timber’, as the timber in question needs to be ‘fire protected’ in order for the new provisions to apply. This is a defined term under a new specification (A1.1) and essentially can be either general timber construction or mass timber construction such as CLT.
For general timber construction (e.g. top plate, bottom plate and stud construction) to be considered to be fire rated, it must (a) achieve the required FRL as specified for the element and must either (b) have a covering which resists the incipient spread of fire for at least 45 minutes or (c) contain two layers of 13 mm fire grade plasterboard. Mass timber, meanwhile, must likewise (a) meet the required FRL but instead of the spread of fire test, the timber must also either (b) be protected with fire rated plasterboard as per requirements for general timber or (c) achieve a temperature of less than 300 degrees Celsius for a time specified in a new table outlined in specification A1.1. Generally, the requirements of massive timber are less stringent compared with those which apply to general timber because of its inherent fire resistance of mass wood.
A further concept revolves around a ‘cavity barrier’ which can either be solid wood or a polythene sleeved mineral walls and which are installed in parts of the cavities around the building in order to prevent the spread of flame and hot gasses beyond the compartment of origin. As outlined above, the existence of cavity barriers is part of the conditions which are required to be met in order for the new timber mid-rise DTS solution to be allowed. As outlined in a new specification (C1.13), these barriers are required in cavities next to separating walls, at separating floors, around doors and windows and according to specified minimum spacing requirements.
Finally, as part of all this, a new concession applies to allow timber staircases in timber mid-rise buildings (D2.25) provided certain conditions are met including sprinkler protection throughout and fire protection below flights and landings at lower levels. This concession applies to mid-rise timber buildings only and is not allowed in the case of traditional concrete and steel buildings.
Ed Knight, a director of Queensland based building certification and building code consultancy outfit Knisco Development Solutions, says the significance of this cannot be understated, especially in light of costs associated with traditional concrete and steel construction in commercial building in terms of concrete workers and labour as well as the number of concrete truck deliveries involved. In their Forte’ apartment building referred to above, for example, Lend Lease used cross laminated timber which was prefabricated, shipped to site and then assembled in a flat pack type of manner. Through using this process, the company says it not only achieved cleaner and safer building processes but also shaved several months off construction timeframes and thus made enormous savings on costs.
Definition of Effective Height
Arguably one of the most important areas of clarification contained within the new Code revolves around the definition of effective height in A1.1 – a critical concept with regard to mid-rise buildings due to onerous fire safety requirements which kick in once the effective height of a building reaches 25 meters or more.
Under the previous definition, the effective height of a building represented the vertical distance from the floor of the lowest storey which provided direct egress to a road or open space up to that of the topmost storey which was something other than merely a plant room. Whilst the lowest storey to be identified under this definition had generally been understood to represent the level at which pedestrians would walk out into the street (typically the ground floor), a Supreme Court ruling in New South Wales several years back interpreted the notion of the lowest storey which provided direct egress to in fact be the point from which vehicular egress was possible. Consequently, whereby buildings contained a basement carpark which provided direct vehicular egress to the street, that would be the point from which building height would be measured – not the ground floor as had been intended under the BCA.
In order to overcome this, the new definition specifies that the lowest storey which must be identified in calculating effective height is now the lowest storey which is used in a calculation of the rise in storeys. Given that BCA C1.2 already contains clear instructions on how the rise in stories is to be calculated and that the guide to Volume 1 indicates how to identify the lowest storey when finding the rise in stories, the effect of this change is to remove the ambiguity which existed under the previous definition especially following the aforementioned judgement.
Knight said the importance of the certainty provided by this ruling cannot be understated. Amid the current apartment boom, he says there are a lot of projects currently in design which are 24 meters in height which previously faced the prospect of becoming 27 meter buildings under the Court’s interpretation of the definition which would essentially see effective height calculated from the basement as opposed to the ground floor. This of course would trigger the additional requirements referred to above and would thus add in all the costs associated with those requirements.
A fourth area of important change relates to the notion of tolerances for staircases.
In 2015, the BCA required constant risers and goings throughout each flight of stairs. According to an information video published on the Australian Building Codes Board web site, this meant that every riser had to be exactly the same height and every going needed to be the same length – a phenomenon which was creating problems associated with atmospheric moisture changes that affect material dimensions or movement in materials that affect stair dimensions.
Under the new rules (D2.13 in Vol 1 and 3.9.1 in Vol 2), a variance of 5mm in now allowed between the height of adjacent risers or the width of adjacent goings whilst a variance of up to 10mm is allowed between the height of largest and smallest risers and between the width of the largest and smallest goings within a given flight.
A further area of clarification contained within the BCA2016 revolves around the use of unisex toilets, whereby separate toilets for men and women must be provided outside of cases where concessions are available whereby less than ten employees work at the premises in question.
This has addressed a situation whereby a number of harassment claims had arisen from cases whereby only unisex toilets had been installed in buildings, Knight says.
Changes relating to provisions for farm buildings have been made in order to address a situation whereby some of these which should really have been classified as class 7 or 8 buildings on agricultural land have instead mistakenly been classified as belonging to class 10a in order to avoid what were in some cases considered to be unduly onerous requirements which were applicable to the former two classifications.
In order to address this, new DTA provisions in a new Part H3 provide concessions relating to egress provisions, stairways, thresholds, services and equipment (e.g. hydrants and hose reels), lighting and sanitary facilities. These apply to two types of buildings, both of which are now specifically defined for this purpose: ‘farm sheds’ which are single storey, generally unoccupied buildings such as stock shelters; and ‘farm buildings’ such as packing sheds which do not qualify as ‘farm sheds’ and are buildings in which people work but which still meet conditions relating to the number of people who typically occupy the building, building size and density of people who typically occupy the building. Because farm buildings contain a higher level of hazard compared to a farm shed, the concessions available to this type of building under the new provisions are less generous compared to those which apply to a farm shed.
New Verification Methods (Structural Robustness and Ventilation)
Finally, in order to further assist with the achievement of performance requirements, verification methods relating to structural robustness and ventilation have been added. Of course, neither of these is compulsory but instead they provide a new option by which compliance with the performance requirements can be demonstrated.
The new method for structural robustness accompanies a new method which was in 2015 for structural reliability, and relates to the performance requirement outlined in BP1.1 (a)(iii) in Volume 1 and V2.1.2 in Volume 2 that where one part of the structure either brakes or becomes seriously damaged, the effect upon the overall building or structure should be limited to that which is reasonable.
According to the new method, compliance with the requirement can be demonstrated whereby a structural engineer is able to demonstrate that the building will remains stable and that the any resulting collapse extends no further than immediately adjacent storeys when any supporting columns, beams or segments of load bearing wall of length equal to the height of the wall are removed. Where a component carries more than 25 percent of the structure, the method specifies that special attention is required to ensure that critical load paths are identified and that the structural robustness of these are considered.
The other new verification method revolves around ventilation and the performance requirements regarding ventilation in order to achieve acceptable standards of indoor air quality (performance requirement FP4 in Volume 1 and P2.4.5 in Volume 2). Under this new method, specific requirements regarding quantities of individual pollutants allowed have been set out in a new table contained in both volumes of the Code which sets out the name of the pollutant, the average time over which concentrations of the pollutant in question are to be measured and the maximum amounts of the individual pollutants in question which are allowed.