42 Berkeley Square

Meticulous evaluation and reimagining of three listed townhouses on Berkeley Square and Hill Street to maximise area and create attractive workspaces with contemporary heritage character.

Client Berkeley Estate Asset Management
Sector Workplace
Size 2,150m²
Location Mayfair, London

Berkeley Estate Asset Management invited us to assess three Grade II listed Mayfair townhouses which had been combined as commercial offices and not been renovated for over 20 years.

Our approach restores the individual buildings at 42 Berkeley Square and 1 & 3 Hill Street, offering three distinct and complementary workspaces.

By meticulously assessing the cluster of buildings, we have been able to create opportunities including increased workspace, a new landscaped courtyard and orangery, a contemporary mansard floor and a garden terrace on the rooftop.

The proposed scheme gained planning consent in October 2025, and we are currently developing the detailed design.

Stuart Le Boutillier, Berkeley Estate Asset Management
“Fathom demonstrated a strong understanding of a complex brief with significant heritage constraints, delivering a sensitive, high‑quality design that successfully meets the needs of modern occupiers. The team were consistently professional, highly responsive and a pleasure to work with, providing clear guidance and confidence at every stage of the process.”

When one becomes three

Our retrofit strategy reinstates the historical integrity of the three individual buildings as distinct properties with their own character.

We adopted a retrofit strategy to revitalise each of the three heritage assets with a series of precise interventions to provide more modern, open plan spaces across the floors.

Our consented proposals start by removing an existing annexe – spatially disconnected from the main spaces – and a mansard roof floor with compromised ceiling heights and poor daylight.

Contemporary structures are then carefully inserted to the building cluster, with the existing buildings fully refurbished to restore and celebrate their heritage features.

From lower ground to fourth floor, we carve out every inch of space to provide uplifting workspaces with a variety of focused, collaborative and social areas.

For building customers, we introduce high quality end of trip and wellbeing amenities and characterful gathering spaces including a landscaped courtyard, orangery and roof terrace.

Our interior design approach balances Mayfair grandeur with the townhouse scale, creating contemporary spaces to meet, connect and exchange ideas.

Courtyard and orangery

Improving energy performance

Interventions are designed to support the heritage buildings transition to a low-carbon future.

We took a holistic view to updating the energy performance of the buildings with new MEP systems, a distribution strategy for added heat pumps and VRF units and upgrades to the external fabric.

Because the three buildings had been subject to phased redevelopment from the 1750’s onwards, there was a degree of uncertainty about which sections of the building dated from which era.

Collaborative research and site investigations assisted the team to determine the age of each part of the building, allowing us to make informed predictions on the structural spans, depths and available zones for servicing.

Heritage staircase

New additions are constructed with high levels of insulation, and poorly performing existing windows are replaced with vacuum glazed units which are thinner and have better thermal insulation than double glazing, whilst retaining historic frame sizes. Heritage windows are restored with upgraded glazing and/or seals to improve their efficiency.

Our combined approach needed to successfully balance the requirements of fire performance, U-value, G-value and reflectivity of the glass within the legislative restrictions imposed by the listed status.

The overall EPC E rating for the combined building is expected to improve to a B, futureproofing the heritage asset and increasing its appeal to customers.

Credits

Architect Fathom Architects
Interior Designer Fathom Architects
Planning Consultant Newmark
Project Manager Storey
Structure Davies Maguire
Services Hive
Heritage Consultant GJHP
Cost Consultant Exigere
Landscape MRG Studio
Lighting Pritchard Themis

Project Information

Credits