Originally two separate buildings built in 1725, 18 and 20 Grosvenor Street were successfully amalgamated to create grade A office accommodation spanning six floors, together with two retail units on the ground and lower ground floors.
Sir Robert McAlpine
Working alongside the client and architect, we worked up the detailed design to incorporate the retained façade to 18 Grosvenor Street, and a new build for the remainder. The front elevations for the new build were stone clad and the rear elevations and lightwell were brick clad – both with inset glazing.
This 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. We worked closely with a number of suppliers to source and adapt a framing and glass design that was feasible but that 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.
A stunning finish to this office building is testament to the lengthy and challenging design phase. A focus on engineering the small, bespoke details paid off with a truly magnificent end product that marries a new build perfectly into the conservation environment it sits in.