The challenge: Designing a 15m high colonnade to run over the top of a working sewer for an office building at the entrance to Slough Trading Estate
The context: The building has been constructed by Wates as a new HQ for property firm Segro, which is developing a series of plots along the road.
On the surface, 234 Bath Road looks like a sleek new-build, characterised by an external structure of white tapered fins, plinths and parapets projecting out from glass curtain walls. However, the three-storey scheme is in fact built around the existing pre-tensioned concrete structural frame of a 1980s office, its basement, and the basement of a demolished 1970s building next door.
Jason Flanagan, design director at architect Flanagan Lawrence, which designed the building, says: “The aim of reappropriation was to save money and improve sustainability. The 1980s building was extended to make the building wider by around 2m, to 15.8m, and considerably longer, extending 40m east towards the new main entrance.”
This entrance is defined by a new portico that extends out 15m from the main building, supported on a series of seven 15m-high fin-shaped columns.
A specialised design was required to prevent the columns from overloading a pipe for the main sewer on the trading estate, which runs at an angle across the site under the floor of the portico, exiting on Bath Road.
The solution: A sewer diversion proved costly and technically difficult, so it was decided to adapt the structure above.
Flanagan Lawrence worked with Wates and structural engineer Capita Symonds to develop a flexible steel structure for the portico, to ensure that the colonnade would be able to achieve the necessary span over the sewer.
The three central columns in the colonnade do not impose any load on the sewer and can be dismantled – the white aluminium cladding is first unclipped and removed, followed by the individual column sections. The canopy above conceals a 1m-deep beam spanning between columns 2 and 6 and over the top of the sewer.
Flanagan explains: “The steel beam between the missing columns at the front of the colonnade had to be deep enough and stiff enough to clear the gap. The need to retain access to the sewer was one of key constraints of the project, even though it is highly unlikely that access will ever be required.”
Photography: Hufton & Crow