Home and Building, Volume 37 Number 6 (1975)
This strongly product oriented report from Australia provides an interesting comparison for readers this side of the Tasman. The potential market size must inevitably lead to some larger product ranges being available in certain areas. However in general terms the market developments seem fairly similar to New Zealand although a few items will be of particular interest.
The variety, made possible by market size, would undoubtedly be of interest to many New Zealand specifiers.
Australia has just been through a period of intense activity in the building industry. One result has been that a highly developed, sophisticated building supplies industry has evolved.
Australia produces building materials which meet world standards of quality and design, and building industry manufacturers export their products to markets all over the world, whilst meeting local requirements. As well as the actual goods, companies have built up world markets for techniques and know-how developed in Australia.
Significant techniques have been developed in Australia, for example, in the field of high-rise buildings. The construction of buildings from the roof down, which is claimed to cut construction time by at least one third and reduce building costs by about ten per cent, has played an important role in several cities.
No conventional cranes, scaffolding or hoists are used. The building is erected from the top down, the roof being constructed first at ground level and jacked up to its final position off vertical elements. Within the roof structure, form work is set up and the service core and columns are cast. Each subsequent section of the work is jacked into position.
Pre-stressed concrete which allows the construction of larger unsupported areas and also makes possible lighter, shallower and more graceful structures without sacrificing strength, has been used to a high degree by the Australian building industry.
Pre-cast concrete, with its savings on erection time, has been called the most exciting of structural materials, and an unlimited variety of structural frames, beams, columns, floor-units and wall-panels for single and multi-storey buildings are currently in use. Additionally, significant use is being made on some buildings of light-weight concrete.
The useful life of pre-engineered formwork can be ten years or more, and the number of re-uses offers tremendous savings when measured against the costs of site-made, tailored form work. This factor has lead to broad use of pre-engineered form-work.
Prefabricated components have come to hold an important place in many types of construction. One Australian company producing modular panelised house offers nine different basic plans which can be constructed from the 22 standard panels in the system.
Designs are in keeping with modern home thinking and finishes are attractive. The homes can be taken from the completed floor to the lockup stage using only factory components.
The only stage of construction where a skilled tradesman is really required is for the layout of the sub-floor channel. Both the channel and the floor must be square and level, with the required degree of accuracy being comparable with that for a conventional home.
The channel, around the perimeter of the floor, is either bolted through to a joist in the case of a timber floor, or cast with splayed bolts into a concrete slab. With the sub-floor channel installed, the next stage in construction is the installation of bottom plates, following the sub-floor channel for external walls, and located according to the plan for internal walls.
The bottom plate for internal walls is a simple channel with skirting for either side of the panel wall already incorporated. External wall bottom plates have the same ready formed skirting for the indoor side of the wall, and a down-turned flashing to the outside. To prevent the ingress of rainwater, a rib more than 20 mm high and facing upwards is formed to create an impermeable water barrier.
The wall panels are installed next followed by the top plate. Final strengthening of the structure, which is already quite rigid because of the inherent stiffness of panels and corner fixings, is achieved with the tightening of integral top and bottom bolts. Since the sub-floor channel is bolted to the floor, the finished structure is highly resistant to wind pressure.
Final step in the construction process is the installation of the prefabricated roof system, which has been widely used on all types of housing and commercial buildings for many years.
The company provides a complete set of documents covering all aspects of construction, so that all the builder has to do is add a site and drainage plan and the drawings are ready for submission to local authorities.page 52