A Plywood House in Australia

Conventional timber house building in Australasia relies upon the construction of a gravity-bearing frame of‘sticks’ that is then clad with an exterior surface. The use of plywood reduces reliance upon the sticks and utilises the engineering properties of the ply to carry loads as well as act as bracing.

Plywood construction requires less material by volume than conventional construction, and if designed on plywood modules, minimises wastage. These assumptions will be measured and in due course once the data has been analysed.

The cost of the house of 120m2 covered area, and 29m2 of verandah was around A$40,000 (NZ$50,000). This excludes builders labour costs, site purchase cost, internal finishes, and electricians labour. It does include foundations, kitchen whiteware, plumbing subcontract and materials including the septic tank system. It is not yet clear how this will compare to traditional construction techniques.

A great advantage of using plywood in construction is that it enforces the discipline of right angles, an advantage for owner builders, as it makes inaccuracies evident whilst there is still time to correct them.It was originally intended to use 7.5mm three veneer bracing ply inside and out. Advice from Boral Handcock Pty Ltd. suggested that there would be unacceptable ‘rippling’ of the surface, and the cost penalty of using 10mm five ply was not excessive. Fixing internal fittings to 10mm ply would, moreover, be more robust thanfixings to 7.5mm.

Experience suggests that the optimum construction might prove to be studs at 0.9m centres using 10mm plywood sheets. This construction appears to be quite rigid and eliminates buckling. 0.9m wide plywood sheetswould be more easily man-handled on site.A plywood stressed skin floor is not necessary unless minimising floor to floor heights is important. It involves a great deal of additional work over conventional constructions.

The Plywood Association of Australia have made a A$10,000 research grant to the Environmental Design and Technology Program at the University of Queensland in which the School of Architecture at the University of Auckland will collaborate. The grant is for a comparison of a number of advanced timber house building techniques, including this, developed by researchers.