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Plant Display House and Herbarium
The Wilds, Johannesburg, Gauteng
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Click to view map Coordinates: | The Plant Display House and Herbarium sits lightly on the high-lying western periphery of The Wilds. The formal architectural layout and design of the building comprises four closely spaced timber framed structures. A contemporary newspaper article published shortly after the buildings had been completed recorded that the four plant display houses were planned to accommodate the following precious plant types: Ferns and Orchids, Aquatic Plants, Tender Shrubs and Desert Plants. The underlying geometry of the plan layout of four separate structures is of particular interest. Each structure was based on a square plan with eight tall composite timber columns supporting a delicate ‘origami’ style roof — the same newspaper article described the roofs as ‘flying saucers’. Each of the four high-level roofs has four ‘folded’ lightweight roof planes with a corrugated translucent fibreglass sheeting to maximise the light ingress. The roofs of the four structures overlap each other on their common edges, making use of the sloping ground level. Common structural gridlines defined the precise layout and spacing of all four structures — see the suggested plan layout accompanying the text. The two diagonal axes of each square building formed four roof ridges — each ridge rising from the centre and extending well beyond the square plan outline to form four dramatic cantilevered projecting ‘prows’. The four corner columns supporting these ridge rafters were all set out at a 45 degree angle to the square plan. The shorter rectilinear axes of each square plan formed four sloping valleys, but with each valley rafter having a lesser projection beyond the square plan. The four columns supporting the valley rafters were set out perpendicular to the square plan. The complex central intersection of the four valley rafters and the four ridge rafters was made with bolted steel plate connectors. The structural timber columns were all fabricated from a pair of substantial glue-laminated Saligna planks separated by narrower recessed laminated Saligna infill plank. This simple construction detail enabled the structural ridge rafters to pass through the centre of the upper ends of each composite column to create a well resolved structural junction. The valley rafters were a composite construction allowing a narrow box gutter to be accommodated between the two main planks. The base of each column was attached to the concrete base with a structural steel plate connection, attached with bolts through the timber column. At each valley column, the recessed infill plank of the column was reduced in thickness to accommodate a recessed square section galvanised sheet-metal down-pipe. The down-pipes continued into a splayed concrete base and discharged through one of the the side faces. Each of the square plant display houses were secured - between adjacent columns - with a full height steel-framed glazed screen or with a lower level steel-framed mesh screen. The Minutes of the Johannesburg City Council record that the Plant Display House and Herbarium was donated in 1966 by Johannesburg Consolidated Investments Co. Ltd (JCI) to commemorate their 75th anniversary — which had taken place two years prior to this. The name of the architect and structural engineer remain to be established. Years of minimal maintenance have unfortunately taken their toll on the building fabric, but the Plant Display House is fortunately still substantially intact. References:
Submitted by: William Martinson, 2020 |
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