128 King's Road, Chelsea SW3
A complex mixed-use conversion turning an underperforming office building into high-value retail at lower levels with premium apartments above, including a mansard roof extension and full M&E renewal.
Mixed-Use Conversion on King's Road
128 King's Road presented one of Chelsea's most compelling development opportunities: a tired 1960s office building on one of London's premier retail streets, ripe for transformation into a mixed-use asset combining high-footfall retail at basement and ground level with three premium residential apartments above, crowned by a new mansard extension.
The planning challenge was considerable. RBKC's high-street constraints demanded that the façade character be maintained while the building's commercial performance was fundamentally upgraded. Our planning team worked through pre-application dialogue with the borough to establish an acceptable envelope for the mansard extension and secure change-of-use consent for the upper floors.
Construction logistics on a busy King's Road frontage required meticulous management. All deliveries were scheduled outside peak retail hours, the scaffold was designed to maintain shopfront visibility for neighbouring retailers, and noise-intensive works were restricted to agreed windows. The party wall relationships with adjoining listed buildings added further complexity.
The completed scheme delivers a Grade-A retail shell at basement and ground with Cat A residential apartments above. The mansard extension provides the third apartment with premium ceiling heights and views across Chelsea. The building now generates significantly enhanced rental income across both its retail and residential components.
7-Stage Project Timeline
From feasibility through to multi-use handover, every stage of this 14-month mixed-use programme was carefully orchestrated.
Initial Brief & Site Survey
Comprehensive assessment of the existing office building including structural capacity for the proposed mansard extension, façade condition survey and analysis of the existing services infrastructure. The client’s brief targeted maximum yield through retail at lower levels with residential above.
Concept Design
The design explored the optimal split between retail and residential floor area, testing different mansard profiles against RBKC’s roofscape policies. The selected scheme positioned a double-height retail space at basement and ground with a separate residential entrance, two apartments on the upper floors and a premium mansard apartment at roof level.
Planning & Approvals
The RBKC planning application required detailed justification for the change of use, a heritage impact assessment addressing the impact on adjacent listed buildings, and extensive pre-application dialogue. The mansard design was refined through three iterations to satisfy the conservation officer while maintaining viable headroom for the top apartment.
Technical Design
The technical package addressed the mansard steel framing, thermal upgrade of the entire building envelope, new fire compartmentation strategy for mixed-use compliance, and a complete M&E design including separate metering for retail and residential. Party wall agreements were served on both adjacent listed buildings.
Construction & Structure
Strip-out commenced from the top down while the ground-floor shopfront was temporarily maintained. The mansard steel frame was erected during a weekend closure, with the new roof envelope completed within three weeks to protect the exposed structure. Internal structural alterations included new openings for the residential staircase and lift shaft, and the retail basement required waterproofing works.
Fit-Out & Finishing
The retail shell was completed to Cat A specification with polished concrete floors, exposed services ceiling and full shopfront glazing. The three apartments received engineered timber flooring, bespoke kitchens, stone-clad bathrooms and integrated wardrobes. The mansard apartment features floor-to-ceiling glazing with views across King's Road rooftops.
Handover & Aftercare
The multi-use handover was sequenced to minimise void time: the retail unit was handed over first to allow the tenant’s fit-out to commence, followed by the apartments two weeks later. Each element received its own compliance pack, EPC certificate and snagging sign-off. The 12-month aftercare programme covers all building elements.
What We Delivered
Retail Shell & Fit-Out
Basement and ground-floor retail shell completed to Cat A specification with polished concrete, exposed services, new shopfront glazing and separate commercial entrance.
3 Residential Apartments
Upper-floor residential reconfiguration with complete refurbishment including bespoke kitchens, stone bathrooms, engineered timber floors and premium specification throughout.
Mansard Roof Extension
New mansard extension with steel framing and thermal upgrade package, creating a premium top-floor apartment with floor-to-ceiling glazing and Chelsea rooftop views.
Full M&E & Life Safety
Complete plumbing, electrical distribution, ventilation and life-safety systems renewal. Separate metering for retail and residential with full fire compartmentation strategy.
Investment Breakdown
How the £2.8M–£3.4M budget was allocated across the major work packages.
Problems We Solved
High-Street Construction
Managing a major construction project on one of London's busiest retail streets with continuous pedestrian footfall and neighbouring businesses.
All deliveries scheduled outside peak hours. Scaffold designed to maintain shopfront visibility for neighbours. Dedicated public liaison officer throughout the build.
Façade Character Retention
Maintaining the King's Road streetscape character while introducing a new mansard storey and upgrading the commercial performance of the ground floor.
Three mansard design iterations to satisfy RBKC. New shopfront designed to complement the established retail rhythm of the streetscape.
Mixed-Use Compliance
Meeting Building Regulations for simultaneous retail and residential use, including separate means of escape, fire compartmentation and acoustic separation.
Dedicated fire engineer from design stage. Acoustic testing at every floor boundary. Separate service risers and entrance lobbies for retail and residential.
Void Time Minimisation
Sequencing multi-use handover to reduce the period between construction completion and income generation from both retail and residential units.
Retail shell handed over first to enable tenant fit-out in parallel with apartment finishing. Leasing agents briefed at snagging stage for immediate marketing.
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Planning a Similar Project?
Whether you are considering a mixed-use conversion, mansard extension or commercial-to-residential development in Chelsea, Kensington or another high-constraint London borough, our team can help.