When Nissan South Africa conceded that the 54 000m² roof of its assembly plant in Rosslyn, Pretoria, had reached its end of life and needed to be replaced, the question was how to go about it.
Since the plant produces more than 50 000 vehicles annually and houses specialised equipment, the disruption of manufacturing processes and incidental damage to machinery during the reroofing operation posed a significant financial risk to Nissan. In addition, the company was concerned about the health and safety of its staff, and considered the risks associated with conventional roof replacement too much of a risk
After extensive consultation with R&D Contracting, Nissan opted for an over-roofing solution, deciding to place a new roof on top of the existing structure.
Practical concealed fix roofing system
For the covering Pro Roof’s Prolok 700 concealed fix roof sheeting system was specified.
According to Stefan Marx, concealed fix manager at Pro Roof, the company’s choice of 0,55mm high-tensile steel sheeting does not weigh as much as many other roofing options. What sets the ProLok 700 system apart, is the unique clip system. “The clips incorporate a steel base and durable TECHNYL®C 216C V30 (a type of Nylon 6.6) extruded anchor towers. The ProLok 700 clip facilitates thermal expansion and contraction of the roof sheet so that the length is not restricted. Also, since “nylon” is non-abrasive there is no chance of damaging the corrosion protection of the sheeting and prevents failure of the long spanning sheeting normally caused by friction.
“Our clip fasteners are attached to the Ashgrid spacers, and the new roof sheeting is clipped onto these brackets. No piercing of the sheeting means that the original roof is completely concealed and the whole system is water tight.”
“We also introduced R&D to COLORPLUS, a steel product from Safal Steel that is produced by a unique, efficient process whereby rolled steel is continuously hot dipped into a 55% Aluminium, 43.5% Zink and 1.5% Silicon Alloy. Delivering a durable coating that has superior corrosion resistance when compared to normal galvanised sheeting,” he adds.
Lightweight over-roofing system
Ash & Lacy’s Ashgrid lightweight steel spacer system proves ideal to provide a structural connection between the existing roof structure and the new outer roof covering. The lightweight steel system creates a defined cavity above the old roof covering and provides a second row of purlins to which the new outer weather sheets can be attached. The project scope required some 30 000 AshGrid spacer bars to be installed.
Bull nosing was done extensively – not only for an aesthetic purpose but also because it eliminates the need for guttering.
“In order to avoid disruption to both R&D’s team and the Nissan workers, the roll-forming and bull nosing was completed at our factory. We delivered it ready-to-use on site. In total, some 7 200 bullnoses were manufactured,” says Marx.
In addition to the main plant, the 16 200m² roof of the stamping plant storage warehouse was also re-roofed with ProLok 700 and Ashgrid spacer system.
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Caption: Nissan South Africa’s assembly plant in Rosslyn, Pretoria, boasts a new roof.