Major Retrofit Project Approved at 1 St James's Square

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• Major Retrofit Project Approved at 1 St James's Square

17 December 2025

Foster + Partners has secured planning approval from Westminster City Council to redevelop 1 St James's Square, retaining over 50 per cent of the office building’s structure.

The Portland stone façade will be completely redesigned, and two new levels with green outdoor spaces will be added. There will be new chamfered windows for optimised air movement, with a mixed mode ventilation system that enables natural ventilation for 40 per cent of the year. 

The building will offer 11,000 square metres of premium office space across ten flexible floors, with a green roof and landscaped terraces.

Foster + Partners aims to exceed GLA targets for embodied and operational energy and meet BREEAM Outstanding, NABERS 5.5* and WELL Platinum.

Luke Fox, Head of Studio, Foster + Partners, said: “Working as an integrated team, which includes our in-house sustainability experts, we are preventing the building from becoming a stranded asset. The decision to retain as much of the existing structure as possible saves embodied carbon, while the introduction of a new breathable façade gives the building a brand-new lease of life.”

Picture: a CGI showing the proposed new design of the building’s façade. Image Credit: Foster + Partners

Article written by Ella Tansley | Published 17 December 2025

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