11 Hanover Street

11 Hanover Street is situated in a highly desirable area of the West End. It is prominently visible from both Hanover Square and Regent Street, offering excellent connectivity and access to the amenities of Mayfair, Soho, and the wider West End. However, despite its prime location, the building’s outdated façade and interiors detracted from its overall appeal. 

The building featured dated elements such as a fritted glass canopy, narrow windows, brise soleil, and an austere entrance, which presented it poorly. The refurbishment and extension project aimed to rejuvenate the building. DLA’s proposals focused on enhancing the street-facing façades to improve prominence, increasing natural light and views, improving the office entrance, and redeveloping all floors and interiors to maximise heights and create new roof terraces. 

The improvements to the façade, though subtle, will give the building a fresh, confident, and clean look. Internally, rearranging the core layout and entrance experience will ensure the building remains a flexible and desirable workspace for the future. 

Constructed in 2000 as high-quality offices for British Sky Broadcasting, 11 Hanover Street features a concrete frame with a unique two-directional waffle slab arranged in a neat 9 by 6 grid. This design originally created distinctive square coffers for lighting and services, though these were later infilled. The façade utilises a bespoke terra cotta rainscreen with matching terra cotta mullions, sills, and reveals, which now appear dated due to poorly detailed overclad mullions and complex joint arrangements. 

The bay windows facing Hanover Street are designed to reflect the Georgian mansion blocks of the Mayfair Conservation Area. However, the irregular mix of double and single bays diminishes this homage. The building’s window apertures dramatically decrease in size towards the upper floors, and it is overshadowed by adjacent properties, further disconnecting it from its historical context. The pavilion-style setback floor with a brise soleil is clad in white clay tiles, had been stained by pollution over the years. 

At the ground floor, a fritted glass canopy over the office entrance attempts to introduce art, adding a unique but dated touch. This project exemplifies the challenges of maintaining architectural relevance over time. 

The redevelopment of 11 Hanover Street revitalises an aging office building to meet modern standards, blending pragmatic improvements with experiential enhancements. 

Key upgrades include expanding the net lettable area through extensions, maximising floor-to-ceiling heights, and increasing natural daylight. These improvements are complemented by recladding the façades, introducing new public art, and installing bespoke coffer lighting. 

Reworking the core significantly enhances the arrival experience by relocating the intrusive lift core from the entrance and upgrading the WCs from cramped cubicles. The retrofit of end-of-trip facilities, previously a garage, also received a comprehensive overhaul. 

These enhancements make the building more functional, aesthetically pleasing, and sustainable, while preserving and celebrating unique features like the square coffered ceiling and adhering to a strict budget fixed from the start.

Our design approach rejuvenates both the façade and interior to create a cohesive, modern space. Externally, we simplified lines, adjusted proportions, and extended bay windows for a consistent elevation. The new terra cotta rainscreen cladding features contemporary double-wide tiles. 

Internally the changes, though seemingly simple, have had a significant impact. Relocating the lift from the central reception area to a position adjacent to the stairs on the upper floors has allowed for a more efficient core, better-positioned WCs, and an increased net internal area (NIA). At ground level, the larger, open reception area offers a clear line of sight to the lift and stairs. 

On the office floors, extended windows and bay additions provide full height glazing and improved natural light. Small extensions on the 3rd, 4th, and 5th floors increase office space, while new terraces on levels 04 and 05 offer private external amenity spaces. Exposed square coffers with bespoke lighting enhance ceiling height and aesthetic appeal. 

Tenants enjoy modern amenities, including shower facilities, lockers, and a bike store, along with efficient MEP equipment and an improved thermal envelope. 

To fulfil the potential of this unique building while adhering to budget constraints, we paid close attention to the surrounding context. Our careful rejuvenation aimed to minimally disrupt the existing streetscape while upgrading the building to become a new neighbourhood asset. This approach was interwoven with our sustainability goal of retaining as much of the original building material as possible, necessitating delicate changes. 

The façades were reimagined in a unit format, with finishes chosen to closely match the existing look. Internally, we exposed and celebrated the soffits, seamlessly extending them into the new extensions.

Reducing both embodied carbon and operational energy are at the heart of the project’s scope. 

Embodied carbon: 

We worked the design around minimising demolition, particularly structure, which reduced the carbon footprint of the works. Where possible, elements were retained, such as window frames where higher performance glazing units were retrofitted into existing. The new terra cotta rainscreen makes use of a natural clay cladding tile with a low embodied carbon and with minimal toxicity. Significant work was undertaken to explore the reuse of existing cladding rails and insulation as well as recycling the old tiles. 

Operational carbon: 

Using a fabric-first approach, we upgraded the thermal envelope, installed high-performance insulation, and replaced the roof insulation to meet current standards. Building systems now rely solely on electricity, leveraging the UK’s decreasing electricity carbon factor. The underfloor air conditioning system, featuring variable speed fans and roof-level heat pumps, enhances efficiency. New air handling units with high-efficiency thermal wheels ensure heat recovery. Extended windows provide enhanced daylight, and LED lighting with advanced controls minimise energy use. An intelligent building management system integrates energy efficiency, comprehensive metering, and user engagement, exceeding Building Regulations Part L2B. 

Despite retaining the use of terracotta, the reclad façades significantly modernized the building’s appearance. The new tile format, enlarged window apertures, dark frames, and vertically extended bays transformed its look. This demonstrates that not all transformations require a complete redesign; maintaining familiar design elements, especially those unique to their context, holds value. While recladding from scratch was considered, it would have resulted in a carbon-intensive and costly approach. 

Other welcome outcomes include: 

• The use rainscreen for the façade also allowed for enhanced thermal envelope upgrades, reducing the amount of internal insulation required to meet todays standard, mitigating NIA loss. 
• Moving the lift core made a dramatic difference on all floors, particularly reception which was not previously welcoming or spatially open. 
• The artwork on Pollen Street was initially designed to span the full width, covering doorways and other elements. However, ventilation and structural considerations during construction led to it being framed and set off from the building line. This adjustment made the artwork resemble a painting, standing out more distinctly from the architecture and allowing it to be appreciated and considered independently. 

Delivering 11 Hanover Square presented unique challenges. Replicating the structural coffers in GRC required careful surveying, modelling, and mock-ups with a specialist subcontractor to ensure an indistinguishable form and finish from the existing structure. In tandem, we aimed to expose and highlight these features, necessitating the integration of cable routes for lighting and fire alarms, which required significant coordination among multiple subcontractors. 

Externally, the cladding package was developed collaboratively with the contractor, subcontractor, and supplier to achieve optimal thermal upgrades within the existing footprint. Numerous aesthetic options for module size, layout, colour, and texture were explored using samples. 

Vertically extending existing buildings often results in complex party wall designs due to irregular boundary conditions, and this project was no exception. A large aluminium rainscreen wall abutted the building along one side, requiring extensive coordination and iterative detailing to extend against this surface. The final solution was a bespoke waterproofing and flashing design that was agreed upon by surveyors, the client, and contractors. 

As public art was important to the building’s contribution to the streetscape, it was reintroduced in the refurbishment. DLA collaborated with artist Catherine Bertola to design a metallic screen for the Pollen Street ground floor elevation, masking back-of-house access while creating intrigue for pedestrians. 

Initial ideas explored pleating and folding fabric, connecting to the area’s fashion history. The design evolved from studying pollen grains, linking to the street’s name, the current use of Pollen Street as a food and beverage destination and referencing food production and biodiversity. This artwork enhances the building’s connection to its social and historical context, reflecting the redevelopment’s ethos. 

Design document can be viewed here.

The existing structure comprises waffle-like slabs with 150mm thick infill supported on 450mm deep ribs. In some locations, including the extension on the upper floors, we have mimicked the square coffer utilising a GRC replica that was made using a mould of the existing coffers. Our proposal involved exposing these coffers to their full extent, with complimentary bespoke lighting and services that showcases the form of the coffer and maximise ceiling height. 

The public art, whilst visually pleasing did form a ventilation screen hiding louvres for mechanical services. Calculations were undertaken to demonstrate their impact on air flow and the design of the artwork was carefully modified to suit. Detail of the waterjet cut pollen spores was also considered from a public realm perspective to ensure safety and security is maintained. 

Morgan Capital – Development Managers

Equals – Quantity Surveyor

Davies Maguire – Structures 

Troup Bywaters and Anders – MEP

Gerald Eve – Planning 

Sweco – Fire Engineers 

Catherine Bertola – Public art artist  

Lumina – Daylight and Sunlight