Grosvenor Square Revisited: Delivering the Next Chapter at Flats 3 & 4

See project W1K 206

Rigby & Rigby is delighted to be progressing works at one of Mayfair’s most celebrated addresses, Grosvenor Square.

Our relationship with this client began with the successful refurbishment and complete reconfiguration of Flat 4, 17 Grosvenor Square, completed in 2022. During the acquisition of the neighbouring vacant apartment, Flat 3, the client identified an opportunity to maximise the potential of both properties whilst taking advantage of Westminster City Council's policies surrounding the expansion and amalgamation of existing residential units.

Working closely with the client and specialist consultants, Rigby & Rigby successfully navigated the complex planning process to secure approval through a Certificate of Lawful Development. This enabled the enlargement of Flat 4 to Westminster's policy maximum of 200 square metres, whilst correspondingly reducing part of the floor area within Flat 3. The result is a carefully considered rebalancing of space that significantly enhances the functionality and value of both homes.

Following planning success, Rigby & Rigby was appointed to provide both architectural and delivery services, working alongside the client's US-based design team, E. Cobb Architects. Together, the teams developed bespoke designs for both apartments, ensuring the client's vision was realised while satisfying the extensive statutory requirements associated with a building of this nature.

One of the most significant challenges involved engagement with the Building Safety Regulator (BSR), as the building qualifies as a Higher-Risk Building under current legislation, exceeding 18 metres in height and containing multiple residential dwellings.

The Higher-Risk Building regime was introduced in response to the recommendations that followed the tragic Grenfell Tower fire in 2017. The subsequent reforms fundamentally changed the way complex residential buildings are designed, approved and delivered, introducing a far more rigorous approval process intended to place resident safety at the centre of decision-making. Whilst these changes have undoubtedly raised the bar for the industry, they have also created a more robust framework that encourages greater accountability, collaboration and design quality throughout the construction process.

The project presented further complexity due to the client's desire to create expansive open-plan living arrangements. Achieving this vision within a Higher-Risk Building required the architectural team to pursue an alternative route to compliance under Part B of the Building Regulations. Through close collaboration with specialist fire engineers, a carefully considered fire-engineered strategy was developed that maintained the integrity of the design while satisfying the necessary life-safety requirements.

Having successfully progressed through the BSR process and secured the final approvals required under the building's Licence to Alter procedures, Rigby & Rigby commenced construction works in early 2026. The project is currently progressing on site and is scheduled for completion in the fourth quarter of this year.

Projects such as this demonstrate the increasingly complex environment in which high-end residential developments now operate. They also provide valuable opportunities to deepen expertise in the evolving landscape of Building Safety Regulator approvals and Higher-Risk Building compliance.

Most importantly, however, this project represents something far simpler: a returning client placing their trust in us once again. There is no stronger endorsement of our team than being invited back to help shape the next chapter of a client's home, and we are grateful for the opportunity.

We look forward to sharing the completed transformation in the months ahead.