Construction Details

Construction Materials

The complex consists of two rectangular buildings with their ridge lines at right angles. The exhauster engines are covered by a simple, barn-shaped, three gables section, the middle gable being the oldest. The middle and eastern gables are about 20 metres long, the shorter western gable about 13 metres and the building is about 21 metres wide. The walls are triple brick, plastered inside in the middle gable and the floors are concrete. The roofs of the two outer and younger gables are slate, but the older central gable has probably been re-roofed, as it is covered with corrugated iron. The two outer gables have wooden trusses inside holding up the roof and simple square industrial windows of 16 panes with wooden glazing bars. The older central gable has a frieze of terracotta tiles on what would have been the exterior walls and are now interior to the flanking gables. Its roof is held up by slender cast-iron trusses with fleur-de-lis shaped brackets. The interior lining of the roof is divided into squares by the rafters and cross beams and each square is lined with diagonal tongue and groove boards alternating in direction in adjacent squares. The windows which still face outside have 12 square panes and arched fanlights with a simple sunburst pattern in green and brown glass. The interior plaster still has the old paint pattern and colours. Barry Brickell has described the machinery in the exhauster house or engine room as follows:- 'The engine room of the Dunedin City Gasworks is typical of those which existed throughout the country in the larger centres. It contains the machinery for low pressure (exhausting) of the raw coal gas from the retorts, via the hydraulic main, through scrubbers, washers and purifiers to the gas holder. This work is done by horizontal steam engines of the old slide-value type doing slow revolutions and directly coupled to a vane type rotary exhauster pump (three examples) or to a reciprocating variety (one example). The latter is a rare and handsome piece of machinery. The equipment was supplied by the British firms of Bryan Donkin (the reciprocating and two vane exhausters) and Waller and Sons (one vane type). The latter is fitted with the usual meyers cut-off valve gear and is a very handsome example of a horizontal engine. The machinery has been respected over the years by gasworks staff who have developed a remarkably respectful and caring attitude towards it. As is shown by the cleanliness and good order of the working parts. There are two other machines of interest in the engine room complex. One is a high speed gas pumping unit driven by a Reader brand, vertical, enclosed-crankcase, piston-valved, steam engine, and the other is a similar unit driven by a 400 volt, DC, open type, electric motor of early design. The rotary converter and impressive, old type, control gear for this unit is also present. The section covering the boilers consists of two higher gables, the northern one having been lengthened at the western end judging by the roof line. The longitudinal interior wall may once have been an exterior wall, judging by the incomplete frieze of terracotta tiles on its north side. The southern gable has corrugated iron on the roof and the north gable has slates. The floors are concrete. The building is about 22 metres long by 16 metres wide. There are two boilers - a fairly modern green cylindrical Anderson boiler and an older, under-fired, multitubular, shell-type boiler, set in brickwork and designed for hand firing with surplus coke. It is fed by a Weirs vertical double-acting steam pump and is a much preferred type of boiler as far as maintenance is concerned. It was built by Dunedin Engineering and Steel Company. It is not the original boiler judging by the trace of an older flue entering lower down on the chimney stack. Each boiler is in a separate room and there is another store room under the addition at the western end. The chimney stack is free standing, has a plastered pediment 1.2 metres high and 3.2 metres square, and a square base rising 25 feet to a concrete cornice. The brickwork is mitred back to run up into the hexagonal chimney, which had steel bands placed up it at regular intervals about two years ago. There are small fire doors at the base of the stack on each of the four sides, all but one of which are bricked up. The chimney is about 80 feet high overall.

Notable Features

The buildings' age and their relatively unmodified condition, along with the range of steam engines and the old boiler. There is no other installation of this kind in Australasia.