Construction World November 2015

Bridge category winner: Kirstenbosch Canopy Walkway (‘The Boomslang’)

The brief could be summarised in a few words: to design a pedestrian bridge between the tree tops of the Arboretum at Kirstenbosch. But the project was indeed a challenging one and is the ‘story’ of how well the whole project team worked together to realise the brief. The walkway was designed to be ‘organic’ and blend unobtrusively into the forest, while minimising damage to the trees. To achieve this, a delicate structure, carefully located between the trees, and finished in a colour that would blend in was required.

“Steel was clearly the material of choice, to satisfy these criteria,” the project team said. To minimise disruption and damage to the vegetation, a comprehensive survey of the area was undertaken. Columns were located relative to trees, and were not necessarily placed at the most efficient structural support positions. Where it was not possible to avoid a particular tree, it was either allowed to pass through the structure, or was tied back to ensure that it experienced minimum interfer- ence from the structure.

Winner – residential category: Zinkwazi Beach House Located on the steep eastward facing slopes above the Zinkwazi beach, the judges said that this gem, using glass window walls framed by an exposed structural steel structure, has unimpeded views from the living spaces. The expression of this building is derived directly from the usage require- ments – enclosed spaces are built in concrete and masonry and open or trans- parent spaces are constructed from steel and glass. “These structural systems define the aesthetic language of the building and speak directly to the functional aspects of the spaces that they enclose,” the project

Residential category commendation: Hennie De Clercq House The key notion behind the De Clercq house in Cape Town on the slopes of Table Mountain is that of outside living, with ‘outside’ incorporating essentially everything on the ground floor, with as few boundaries as possible. Thus the single, large living room, encompassing the kitchen dining and lounge area, opens to the patio on the one side and onto a wide ‘stoep’ without columns on the other, bordering on the fynbos garden. A structure consisting of I-section beams and columns enables the open plan and the cantilever ‘stoep’, while carrying most of the storey above. Much attention was given to the details and finishes of this structure as it constitutes a key architectural feature.

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House De Clercq and cottage, Mount Verde Set in an agricultural estate, surrounded by sugar cane, this house is a perfect example of what LSFB methods are meant for. “It is true to the material and does not look like a LSF house trying to look like a brick home and the early involvement of the contractor with the design team enabled them to push the limits of LSFB,” the judges said. “With a clever mix of a LSF system, with plated LSF joists and some hot rolled steel they were able to achieve the client’s desire for an industrial look with thin sharp lines to produce a world class, beautiful up-market home,” said the judges Mediclinic, Midstream Due to the early involvement of the LSF contractor and profile supplier, the architect was convinced that the design should include a LSF roof structure to reduce the total load on the supporting structure. The Ultra-Span (a pre-fabricated light gauge steel roof truss system by MiTek) roof structure covers 9 100 m² of the roof structure and weighs in at almost 68 tons of steel. This comes to just below 7,5 kilogrammes per square metre, including purlins, which is extremely light considering some of the roof trusses span 19 metres with considerable live load and bottom cord loading requirements. The design also allowed for supporting 100 mm-thick FBI insulation between the truss top chords and the purlins. Joint winners – Light Steel Frame Category: House De Clercq and Cottage and Mediclinic

CONSTRUCTION WORLD NOVEMBER 2015