Page 60 - Build 161

Building controls
Although the code provides some details, for example, a table of allowable stresses permissible for structural timbers by timber species, it is mostly prescriptive. One example is, Wood studding shall be not less than 2 by 4 inches and spaced not to exceed 16 inches on centers.
It is likely the BCC expected those likely to use the code would be well trained, experi- enced and likely to know their construction materials. These expectations would be buttressed with a good dose of inspection and the potential for legal consequences.
The 1922 code was possibly the rst code anywhere that included exploration of going beyond the minimum. It used the research to identify the need for a range of requirements in response to local conditions including wind, snow, earthquakes, moisture, sound, vermin, insects and the correct use of thermal insulation.
Base for other codes, including NZ’s
The BCC code found a major use in the development of the 1927 Uniform Building Code prepared by building o cials on the temperate west coast. This, along with other BCC publications, supported the develop- ment of the 1945 Standard Building Code widely used in the southern states and the 1950 Basic Building Code used mainly in the north central and eastern states.
In 1997, these three codes merged into the International Building Code, making the 1922 code the grandparent of the modern US building code.
This 1922 US building code also travelled to New Zealand, where it was used to create the rst New Zealand national Building Code in 1924 – but that is another story.
Note This research was funded by a Fulbright New Zealand Scholarship and supported by Victoria University of Wellington.
Building Code turns 25
This year marks 25 years since the New Zealand Building Code came into effect.
BEFORE THE early 1930s, many New Zealand councils had their own building bylaws, although some had no requirements at all. Often adjacent councils had di erent rules, causing di culties for architects, builders and material suppliers. While some local issues were considered, the bylaws were often based on overseas experience – notably Britain.
Changes after Napier earthquake
The 1931 Napier earthquake changed everything. Overnight, it became evident that construction methods that worked well half a world away and had locally for some years were unsuitable for use in the Shaky Isles. The poor performance of heavy unreinforced masonry that was widespread around the country but had caused signi cant loss of life in Napier was cause for particular concern.
The country clearly required some form of building standard. In 1935, NZSS 95 Standard Model Building Bylaw provided a uniform but prescriptive basis for local bylaws. It was followed in 1964 by NZSS 1900, but local changes still led to unnec- essary di culties.
It was an easily enforced cookbook-style of building control, but many believed it sti ed innovation and the use of new mate- rials. Nevertheless, the system remained in place until the early 1990s.
1992 saw performance-based building controls introduced
The Building Act 1991 was a remarkable departure from the old way of doing things. Not only did it merge many of
the existing Acts and regulations, it intro- duced the concept of performance-based building controls. At the centre of this sea change were the Building Regulations 1992, in particular, Schedule 1 – the New Zealand Building Code.
The Building Code marked the begin- ning of a new way of thinking about quality for the building industry. The old, prescriptive guidance was gone. In its place was a new set of minimum performance requirements that all new buildings had to meet.
Local authorities became the day-to-day administrators of the new system, taking responsibility for ensuring that all building work in their jurisdiction met or exceeded the new performance requirements. For a period, the owner could choose to use a private building certi er to check technical proposals and perform inspections.
Guides helped to overcome confusion
In the absence of practical guidance explaining how to build, the change caused some confusion. A series of guides explaining performance-based building controls and how to implement the Building Code went some way towards helping the industry embrace the new system.
Over the last two and a half decades, the Building Act and the New Zealand Building Code Acceptable Solutions and Veri cation Methods have been changed and updated many times. However, the Building Code, with its forward-thinking performance-based requirements and focus on occupant health and safety, remains in place to this day.
58 — August/September 2017 — Build 161
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