20 Grosvenor Street is a new Grade A commercial office space, successfully brought together from two neighbouring buildings.
Sir Robert McAlpine
Colorminium were engaged by main contractor Sir Robert McAlpine whilst the design was still at Stage D. Working alongside them and the architects, the detailed design was worked up through Stage E before the design responsibility rolled over at commencement of Stage F. Featuring a retained façade to 18 Grosvenor Street, the remainder is new build with the front elevations stone clad and the rear elevations and light well brick clad – both with inset glazing.
A very high quality project with a prescriptive architectural intent that had been driven by Westminster planning authority had a big challenge in that it could not be achieved with proprietary systems. After being engaged, Colorminium worked closely with a number of suppliers to source and adapt a framing and glass design that was feasible but carried a number of risks requiring mitigation.
A further key feature of the design was the maintenance of the weathering and performance lines on the envelope. The contractor and architect had opted to clad the frame in pre-cast panels mainly due to the complex logistical challenges and party wall abutments, which meant close co-ordination was required to ensure the interfaces were carefully detailed.
With insert windows to the stone and brick facades the building had lightwells down each party wall flank which had rooflights installed at ground level giving natural light to the basement. At rooftop, the top floor was clad in curtain walling with brise soleil to the south facing elevations. The main entrance onto Grosvenor Street had a complex pure bronze portico design that incorporated several key features such as rainwater goods and access control.