TOPEC, the modular slab formwork system from SGB, has enabled north west based concrete frame specialist SGG Construction Ltd to meet a demanding fast-track programme for the construction of a major new office development at Stephenson Square in Manchester. The system, used on site at The Hive in the city centre successfully achieved the concrete quality finish specified by HKR Architects where large areas of soffits were left exposed on the completed building.
The £11.5 million, 110,000 sq ft sustainable office building in Stephenson Square is designed to meet the needs of a new breed of commercial market that demands low environmental impact and optimum flexibility of tenancy. With a project completion date of January 2010, main contractor Bardsley Construction set testing deadlines for all their package subcontractors and SGG Construction were required to complete the primary concrete frame in a build period of less than nine months.
Due to the logistical constraints of the city centre site, SGG Construction had to source a suitable alternative to traditional formwork methods. It was at this stage that SGB were approached and they proposed the TOPEC® slab panel system, a simple and cost-effective modular formwork solution, comprising of just two basic components. The system is designed to achieve high output rates in conventional building applications.
For ceiling heights of up to 3.5m, TOPEC® is easily erected from below, thereby reducing the requirement to work at heights. At The Hive, HKR Architects designed ceiling heights to less than 3.4m in order to reduce building volume and facilitate a more efficient heating and ventilation system. On the ground floor, which is to be utilised for retail space, the ceiling height exceeded this and reached an increment of 4.5m. Here the TOPEC® LIFT, which is a custom-designed remote-control scissor lift, ensured quick, efficient and safe installation of the slab formwork.
From SGG Construction’s point of view, the simplicity and speed of the TOPEC® system achieved the goal of fast erection and dismantling while also reducing the space required for storage and assembly. The TOPEC® system met all the key criteria, including the overriding need to safeguard the health and safety standards of the workforce. Furthermore, it proved to be compatible with traditional formwork, which reduced the cost outlay.
SGG worked closely with SGB’s management team for several weeks prior to commencement of the works in November 2008. SGB supplied sample drawings and panels, as well as organising visits for the contractor and architect to see TOPEC® being used on live sites.
One of main architectural concerns was the quality of the surface finish sometimes produced by panel formwork systems. “The concrete will be exposed and the need to achieve an architectural grade, smooth finish is paramount to the quality of both the materials and the success of the design”, explains HKR project architect, John Crellin. “The TOPEC® panels can deliver this requirement, achieving the desired finish” he adds. “However, we had to work closely with SGB to co-ordinate the alignment of the formwork seams”.
The design challenge provided by the system was that the large-format TOPEC® panels measure 1800mm x 1800mm whereas the building had been designed on a 1500mm planning module. “The formwork and the planning grid did not correspond and therefore required design coordination and manipulation of the TOPEC layout establishing a modulated and considered soffit that expressed the building’s structural grid”, stated John Crellin.
Working directly with HKR, SGB engineers developed a design which optimised the TOPEC® panel layout, using a small volume of traditional formwork to express the structural grid around the column penetrations. Close communications between SGB and the architect also helped co-ordinate the lighting layout in line with the original concept.
By the time SGG started work on site in November 2008, all the design details had been laid out and work could progress without delay. Ease of manual handling reduced the manpower required as well as avoiding the need to crane-in any of the formwork sections, as traditional methods would have required.
By the end of June 2009, SGG Construction Ltd had completed the concrete frame on the programme, allowing Bardsley Construction to progress on schedule for hand-over to the client in January 2010.