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Home and Building, Volume 37 Number 6 (1975)

Systems: A sandwich panel technique

page 32c

Systems: A sandwich panel technique

The majority of potential home owners are concerned initially, and often solely, with two factors — price and time (i.e. completion date). Obviously the client is expecting the best quality, planning and finish consistent with his available funds.

In the interests of the best compromise on these factors, manufacturers generally have in recent years paid more attention to developing building systems which have as their aim the maximum performance for the client under the various areas of importance.

The Corcelite Building System — a system which was ten years in the development and refining stage — is one of the techniques gaining growing acceptance both in New Zealand and overseas.

It is not modular housing — in fact, it is truly a system, a technique using factory produced sandwich panels of standard dimensions thus increasing in-factory portion of the house and reducing on-site time.

The main elements of the system are these — the use of a sandwich panel walling system which is integrated to any one of a wide variety of conventional timber, masonry or concrete floor and sub-floor treatments; the utilisation of prefabricated roofing trusses which are tailored as a standard technique to the top of the panels; the nature of these trusses dictates that the finished house features a conventional flat ceiling.

The system has been developed with a view to achieving high factory volume and then distributing the houses for final erection to a range of approved outlets. One motivating force behind the system was a continuing pressure from several overseas markets for houses which could be supplied and quickly erected from a 'package' containing all elements.

Whilst the system is available in a series of standard designs the individual has flexibility both through the wide range of sizes of house and many areas of finish where personal preference may be given rein. Houses are available from 1000 to 2000 sq.ft. approximately varying in the particular requirements of sleeping and living areas catered for.

Central to the system is the 50 mm thick panel itself — standard exterior walls feature asbestos cement sheet on one side with a continuous polystyrene core and hardboard inner surface. Alternative exterior finishes available are marine grade vertically grooved plywood cladding and PVC extruded vertical sheathing.

The interior partition walls are double faced with hardboard on honeycomb cellular core. The asbestos cement exterior is available in either of two standard colours; however, at the interior stage scope is allowed for personal preference — in addition to paint and paper treatment various other textured fabrics, vinyls etc., are attractive alternatives. One other flexibility available to the purchaser is that within the scope of the module window and door positions in the exterior walls may be altered.

The external wall sandwich panels have excellent acoustic and thermal insulation figures which are popular in today's energy and pollution conscious market. The polystyrene core has the inherent fire ratings of the material but tests prove it to be in no way inferior to many walling systems. However, current exploration shows the possibility of a core utilising urea formaldehyde — a material with improved fire ratings.

This introduces the point that the manufacturers stress — that continuing tests in product evaluation are under way with a view to maintaining the quality and performance of the system.

The essential companion to the laminated panels in the Corcelite system is the specially developed range of sections for interior and exterior use. These mouldings, many of which are extruded PVC, play a crucial part in the streamlined erection of the panels whilst at the same time they ensure complete waterproofing at all points.

In addition to couplings to join the panels themselves and the latter to floor and roof supports, other sections supply skirtings, architraves, door jambs and window finishes.

The installation of services in this system is very simple. Electrical cabling benefits from being placed within the vertical coupling cavity free from studs and nogs. Plumbing connections have been well catered for by the development of special fittings. Experience shows that it is preferable in all buildings, to have plumbing joints and piping where direct access is possible. Thus when pipework from below the floor enters the kitchen, bathroom, laundry and other wet areas it is concealed in standard cupboard and unit enclosures which these days are almost always added to kitchen, bath and sink areas.

Special aluminium joinery has also been developed for this system to ensure a reliable marriage between the panels and sash members. In fact, the interface between windows and walls must be the equal of any window on the market.

The system has obvious advantages on account of its factory control and reduced on-site time. A two-man team can erect a house in under 50 percent of the time taken on a conventional dwelling. Apart from other factors, even the weather has less scope for interference.

The versatility of the system is such that it can be equally applied in either one or two storey properties.

The export potential, already being realised, could be one of the big advantages in building maximum economies of scale in the production of the basic panels.

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