One enters the floating building by means of a weathering steel bridge with a timber deck walkway. The lowest floor contains a living area and kitchen, with two double volumes and a circular stair linking the living area visually and physically to the bedroom level above. Large sliding doors, 6m high, open up the living level to a balcony overlooking the estate’s gardens
A circular stair, with sculptural treads carved from solid standing laminated oak, and supported on weathering steel reaches, lead up to the bedroom level (with bathroom), and then further up to a roof deck with views over the Constantia Valley.
The structural system was executed in laser-cut weathering steel plate, bent to form facetted columns, branch-like arms and rings. There are 4 structural column clusters, each consisting of 4 weathering steel columns held together with the arms and rings, to support spruce and western red cedar floor beams. The columns are bolt fixed by means of a large circular baseplate on conical concrete pad footings.
There is no steel connection between any of the steel structural columns but the timber floor plate construction. The stair “drum” consists of a half circular lattice framework of mild steel hollow tubing and angles – bracing the structure as it is bolted down onto a concrete drum at ground level (where the building’s utilities are concealed behind a slatted timber screen). All shapes cut from the weathering steel plate had to fit into the laser cutter’s maximum size restriction, as well as the allowance for shapes that can be folded. All components of the steel structure needed to be transported to a site with narrow driveways. The house is situated high on a slope without any direct vehicular or crane access. Components were pulled to the site on a sleigh with a winch, and then hoisted up by means of a gantry supported by scaffolding surrounding the house site. Getting building components to a remote part of the site that is inaccessible by road proved challenging.
Some of the larger components were winched up an embankment to the position of the construction site. The site was enclosed ina scaffold structure that was covered with a tarpaulin and hail netting so that work could take place during the rainy season. Chain blocks were attached to two I-beams at the top of the scaffold structure to raise and lower components into position.
The slender nature of the vertical steel structural elements meant that there was flex in the structure when loaded and the steel structure had to be braced prior to the timber being installed. What makes this project special is the high level of customization and detail required, with very small manufacturing and assembly tolerances. Steel was used to express the natural structural systems of the trees surrounding the house.
|Tons of steel used||Corten 0.9184 tons | Mild Steel|
|Structural profiles used||76x76x3.5 square hollow section | 76x38x3.5 rectangular hollow section | flat plate of various thicknesses|
|Project Team Role||Company|
|Client/ Developer||Graham Paarman|
|Architect||Malan Vorster Architecture Interior Design|
|Structural Engineer||Henry Fagan & Vennote|
|Quantity Surveyor||DA Quantity Surveyors|
|Main Contractor||T. Naude|
|Steelwork Contractor||Link Engineering|
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