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Superstructures Steel – smartly built

Superstructures and sister company Agristructures fall under the umbrella of The Steel Building Company (Pvt) Ltd. Agristructures, as the name suggests, specialises in catering for the agricultural industry, in particular providing storage, sorting sheds and drying tunnels for tobacco growers. Other applications for their steel buildings include massive storage sheds for farm implements like tractors and harvesters, workshops, greenhouses for horticulture, and poultry sheds. Previously known as Car Guard Construction, Agristructures was formed in 1984, so they have over 30 years experience in building steel structures.

In 2006 Agristructures diversifed into supplying steel structures for the mining industry including plant workshops, material stores, administration buildings and laboratory buildings. They have completed several successful projects for First Quantum Minerals and other mining companies in the DRC and Zambia. In 2014 The Steel Building Company was formed with Agristructures continuing to focus on the agricultural industry and Superstructures focusing on more commercial and industrial projects.

While continuing to build commercial and industrial projects locally Superstructures has also completed a number of shopping centres in Mozambique (including in Pemba, Tete and Nampula), the Waterfalls Mall in Lusaka, and Solwezi City Mall in Zambia. Their work in the region with a wide variety of international companies has allowed them to gain valuable experience and keep up with the most current construction trends. Recent projects in Zimbabwe include the new Bathroom Boutique warehouse in Bulawayo, and Halsted’s warehouse and retail centre on the corner of Harare Drive and Alpes Road.

Their latest highly successful structure is the 14,000 sq. m. warehouse situated at 41 James Martin Road in Workington, Harare – a private equity investment managed by INVESCI Asset Management (Pvt) Ltd on behalf of a number of local Pension Funds. The warehouse was offcially opened in June this year and took around 13 months to complete, including the demolition of the existing offces and workshops on the site. This was a complete turnkey project with Superstructures managing every aspect of the build, including the initial ground works and the concrete foor slab, and sub-contracting other service providers for the plumbing, the electrics and the lighting, and the fre sprinkler system and offce ft out.

The warehouse employed Superstructure’s new Seamlok 745 concealed fx roofng system which is a ground-breaking innovation for the construction industry in Zimbabwe. (Currently Superstructures is the only company to have a machine based out of Zimbabwe.) The Seamlok 745 system has a number of important advantages, most importantly the concealed fastening system means that there are no holes punched through the roofng sheets for the fasteners. Secondly, the currently used system of fxing roof sheets with conventional “pierced fx” fasteners into the underlying lip channel purlins locks the roof sheets to the purlins.

The roof sheets expand at a different rate to the purlins, and the underlying structure supporting the roof, and something has to give, so the holes for the fasteners get bigger and/or the fasteners come loose, inevitably leading to leaks as the building ages. This is not apparent on our old angle iron purlin structures with hook bolt roof fasteners as the hook bolts could move with the roof allowing the roof the expand independently from the structure. The roof sheets can move up to 1mm per metre so over a large span the movement can be quite signifcant. On longer spans, the concealed fastening system uses sliding clips so that the roofng sheet can expand over the purlins freely tO allow for the contraction and expansion of the sheets at different rates to the structure in response to weather conditions.

The system employs a mobile rolling machine so that roof sheets are rolled on site to the required length. The rolled forming mill can make sheets up to 60m in length so there are no horizontal joins where shorter sheets would normally overlap. This method reduces wastage and overlaps. The machine can roll steel roofng coil from South Africa or from other international suppliers in thicknesses ranging from 0,47mm to 0,8mm using galvanised steel, Chromadek (manufactured by ArcelorMittal), Colour Bond or Zincalume. Zincalume has a zinc and aluminium coating which makes it up to 20% more resistant to corrosion than galvanised steel. This makes it ideal for use in coastal regions where the sea salt causes oxidation.

Roof sheets are accurately cut by a CNC (Computer Numerical Control) guillotine reducing the chances of rust forming on the ends of the sheet, cutting the sheets with an angle grinder burns the galvanised protective coating which is then susceptible to corrosion. The side laps are mechanically joined as the roof is laid, using a crimping machine that runs along the two sheets. The crimping machine creates a 360 degree double lock seam that is extremely weatherproof, with the concealed fxing clips are folded within the seam.

The seam is higher than the roof panels and the profle has deep troughs so the fnished roof can cope with higher volumes of water with no chance of leaks. Because the sheets are so water tight the pitch of the roof can be signifcantly reduced – even down to 3 degrees over 60m spans – and still perform better than most conventional roofng systems. This results in further savings on material costs and also reduces the height of the apex on large span structures.

Another innovation in the design of the warehouse at 41 James Martin is that there are no skylights cut into the roof sheets. Conventional skylight panels have a tendency to leak, deteriorate faster than the roof sheets and are responsible for 90% of serious or fatal roof accidents. The 41 James Martin roof has a central ridge of translucent sheets that runs down the length of the building. The translucent sheets are UV stabilised polycarbonate. From the ridge the roof sheets extend outward on both sides for 15m to a vertical section of more translucent sheets which are 1,2m high. The roof was deliberately designed to have a step in the middle of the roof slope with translucent sheets ftted to the vertical section allowing for good natural internal lighting. By doing this there are no translucent sheets within the roof as is the conventional practice. The roof then extends a further 33m to the edge of the structure where it meets another vertical section of translucent sheeting that runs around the whole building.

Thus the interior has more than adequate natural light. This pioneering architectural design has been exclusively developed by Superstructures and is a new concept in Zimbabwe for roofng and lighting solutions. Interestingly, from the outside the translucent sheets are almost exactly the same colour as the Chromadek cladding so they blend together seamlessly. All of Superstructure’s steel buildings are fabricated in modular form in their 6,000 sq m workshop in Willowvale in Harare. They have the cutting, welding and jig equipment to manufacture fabricated I-beams (taper fange plate buildings), castellated or cellular beams, heavy rolled plate structural tubes, lattice trusses and portal I-Beam structures. Installation and erection of their structures is undertaken by skilled and experienced teams using Superstructures’ own cranes and equipment. If customers want to undertake their own installation Superstructures can provide a skeleton crew to assist.

Superstructures use Tekla BIM (Building Information Modelling) for all our shop detailing drawings– a programme that provides detailing facilities and quality control procedures, providing a 3D model for clients before manufacturing starts. The programme also helps to simplify, control and speed up the construction process reducing project costs. For more information contact: The Steel Building Company 74 Woolwich Road, Willowvale Call cell 0721 221 207 Land lines 621540/621584 or 8677000698/9 Website: Email:

text by Michael Nott

photos and plans supplied by The Steel Building Company and Invesci Asset Management (Pvt) Ltd

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