A five-storey, 11,150 sq m Grade A office building plus basement parking and landscaping. The building is on the site of a former council car park and directly adjacent to live rail tracks.
The structural frame is reinforced concrete with post-tensioned floor slabs with a raft foundation at basement level. This form of construction was a highly efficient way of achieving the required 12m x 9m grid. The concrete has been left exposed to maximise its thermal mass properties, and to provide an acoustic barrier between the internal spaces and the adjacent rail line. A cantilevering section over the pavement creates an extra 260 sq m of office space and uses post-tensioned slabs and diagonal steel bracing.
A dominant architectural feature is the glazed entrance facade and external solar shading, supported and restrained using exposed tubular steel columns. The glazing panels are secured back to the columns with a system of steel transoms and mullions, carefully detailed for movement and thermal bridging. All steelwork is exposed, and so particular care was taken to detail an elegant and high-quality finish.
The site had many constraints, including the mainline railway, a petrol station, residential properties, existing mature trees with protected root zones, bat roosting sites, and an existing live sewer crossing the site. All constraints were carefully considered, and we took an active role in managing and liaising with the external stakeholders and project team. At an early stage in the project we negotiated with and gained approval from Network Rail to demolish the existing multi-storey car park and to excavate for the new basement. We gained approval from Thames Water for the existing sewer to be diverted. Our work ensured there were no delays to the programme or unexpected changes required to the design.
The new building car park ramp potentially undermined the neighbouring Network Rail South West (NRSW) line. With the geotechnical specialist and the main contractor, we developed an approach with a cost saving combination of open cut excavation and King Posts with robust monitoring controls. This was achieved through supplementary site investigation, slope stability analysis, temporary works design and exemplary multi-hierarchy protocols for monitoring and trigger level action and contingency planning. As a result, NRSW Asset Protection now adopt this model for monitoring controls as a benchmark on their other projects.
The building achieved an Excellent BREEAM rating.