Clean COLORBOND™ ULTRA steel, a pre-painted AZ200 roofing material manufactured by BlueScope Steel, was recently used in the demolition and re-building of the Blue Route Mall. The mall is a popular shopping destination in Tokai, a southern suburb of Cape Town. BHF de Jager was appointed as the project manager and he worked closely with Aveng Grinaker LTA, the main contractor for the project. Louis Karol Architecture was responsible for the design and Scheltema was appointed as the roofing contractor.
In total, 58 000m2 of double-level shopping area was added to the mall, and a further 29 000m2 of parking was added in the basement. The project took 23 months to complete the building work. Construction of the parking area is now underway, and will be followed by the completion of the demolition work of the old structures.
Pre-painted white steel was formed into Ziptech 420 by Hulamin for the main roof covering of 30 000m2. The product was also formed into Ziptech XT cladding and used as Cladtech F350 panels for the eaves and soffits.
According to Lance Wilson from Hulamin Building Specialists, Clean COLORBOND™ ULTRA steel was specified for its cost-effective corrosion resistance, the durability of the substrate and superior coating. A list of criteria was used to design and specify roofing materials that would hold up in the windy and often stormy wet conditions that rake the South Peninsula.
The roofing systems had to have a water carrying capacity and the roof needed to offer sufficient resistance to the ingress of water, due to the profile height and standing seam lap design that was used in this project. The product specified for this project needed to have the ability to reverse smooth curves and meet the criteria via single long reverse smooth-curved sheets. The roofing systems had to add to the aesthetic features of the roof and should produce negative wind resistance due to the seaming of upstands.
In the end, white pre-painted roofing material was chosen for energy conservation reasons, due to the high solar reflectance index (SRI) value of BlueScope Steel’s colour, Amazing White. “The white colour chosen by the designers of the Blue Route Mall upgrade provides an ideal cool roof,” says Wayne Miller, the BlueScope Steel head of operations in Southern Africa.
He further explains that the unique paint system used on all colours of the entire Clean COLORBOND™ steel range incorporates various essential sustainability features such as high reflection of incoming solar radiance, exceptional colour retention, anti-chalking and dirt resistance. “Similar material was used in the construction of the South Africa Container Depot near the Cape Town Harbour – the industrial category winner in the Southern African Institute of Steel Construction Steel Awards 2010”, says Miller.
Roofing systems that optimise levels of performance
To enhance a project’s rating under the Green Star system or simply in promoting sustainable building practices during refits, as a Green Building Council of South Africa (GBCSA) member company, BlueScope Steel recommends that roofing systems should optimise levels of performance and lifespan, in addition to minimising their carbon footprint.
BlueScope Steel defines sustainability in roofing as a system that has a long service life and is ultimately recyclable. “Dematerialisation of the substrate and the coating that has a lower coating mass, but also produces better performance, is an important factor,” says Miller. “A sustainable roofing system should also reflect the maximum amount of incoming solar radiation via an advanced infrared coating system,” he adds.
Under harsh climatic conditions, especially within the sensitive 5km coastal zone, Miller advises clients to use only premium grades of alloy-coated steel such as ZINCALUME® and pre-painted steel such as Clean COLORBOND™, all manufactured with a 55% aluminium, 43,5% zinc and 1,5% silicon coating (AZ150 coating), or to gain a much longer service life. This advice is based on the company’s multiple years of experience in the aggressive climatic conditions of Southeast Asia, Australia and over 12 years product performance in South Africa. “If you are building in severe industrial environments where there are aggressive fumes or particulate fallout within a 200 meter radius or if the location is within 100-400 metres from the sea, we would recommend using our Clean COLORBOND™ ULTRA. This has an AZ200 coating, in this case coated to a mass of 200g/m2 over the steel substrate.” He concludes by saying that if correctly applied, their products should give a lifespan of up to four times longer than the standard pre-painted galvanised steel roofing systems.
BlueScope Steel Southern Africa (Pty) Ltd.
Wayne Miller, general manager
Tel: 021 442 5420