Project leaders from Hale Brown Architects, Glass Box Facades, and Schüco discuss the collaborative processes and technical challenges behind the façade of 114a Cromwell Road, London, with AT’s Technical Editor John Ramshaw.
In association with
At the heart of most successful façade designs is a story of collaboration, teamwork and ingenuity. In this new technical series, sponsored by Schüco, we explore these important and revealing processes through a standout project submitted for the Schüco Excellence Awards. The fourth article in the series explores 114a Cromwell Road, a sensitively refurbished and extended office building in Kensington, west London. Completed in 2023, the 3,700-square-metre project was designed by Hale Brown Architects and delivered in collaboration with structural engineer Peter Dann, specialist façade contractor Glass Box Facades, main contractor DE Group Contracting, and façade, window, and door solutions provider Schüco.
Back to the future
Constructed in the 1970s, 114a Cromwell Road was a tired and outdated office building located at the intersection of Cromwell Road and Grenville Place. Hale Brown Architects’ sympathetic reworking includes a new office floor (level six), a visually-striking, glass and metal-clad entrance and core structure, as well as high-performance commercial interiors throughout.
Externally, prominent zig zag brick detailing sets up a series of clearly defined window bays and a strong vertical emphasis across the existing east and west façades. This architectural motif is adapted and reworked by Hale Brown, taking the form of angular, metal-clad bays framing sliding glass doors on the sixth floor; and a series of six-storey-high, tightly-folded zig zag glass ‘slots’ articulating the east and west sides of the re-clad entrance and core structure.
High-performance Schüco window and door solutions combined with meticulous detailing and skilful installation are central to the success of both the retained and reworked façades. FWS 60 curtain walling is employed on the core for the zig zag windows, while FWS 50 curtain walling and ASE 60 sliding doors are combined on the sixth floor to maximise view out, daylighting, and access to the generous roof terrace. Elsewhere, AWS 70.HI (high insulation) windows set within metal-clad dormers are used on the fifth floor, and ADS 70 HD (heavy duty) doors are deployed on the ground floor. The Schüco door and window systems specified also significantly enhance the thermal performance of the building envelope, which was a key aspect of the project brief.
Rising to the challenge
“The original design intent for the zig zag façade was a structurally-glazed solution,” explains project architect Dan Terry. “However, DE Group Contracting was appointed under a design and build contract, and they put forward an alternative solution using the Schüco system as a contractors proposal, which was accepted by the client. The key design aspiration was to maintain the glass-to-glass junctions as much as possible in order to ensure good levels of daylighting and maximise views out with as little visual clutter as possible.”
Glass Box Facades was contracted by DE Group Contracting to design, manufacture and install the Schüco curtain walling, windows and doors. “We already had a strong track record of successfully delivering complex refurbishment projects in collaboration with DE Group Contracting and Hale Brown Architects, which allowed us to begin from a foundation of mutual trust,” says company director Steve Dibley. “It was clear from tender stage that the most challenging aspect of the scheme would be the zig zag glazing, which spans from lower-ground floor up to the fifth floor,” continues Dibley. “We quickly recognised that due to the height of the screens and significant building movement, a frameless structural glass system – as originally proposed – would not be feasible. Collaborating closely with our designers and structural engineers, we refined the concept into a hybrid solution. By integrating Schüco FWS 60 curtain walling profiles with structural glass-to-glass corners, we preserved the architect’s aesthetic vision, while achieving the necessary structural and thermal performance of the façade.”
Glass Box Facades was supported by Nick Silk, Key Account Manager at Schüco, throughout the tender process. By providing clear and concise specifications and maintaining open communication with Glass Box, the manufacturer ensured a smooth transition from design to construction. “Early engagement with the project team facilitated the seamless integration of Schüco systems into the design, allowing for the incorporation of detailed sections and ensuring the feasibility of the proposed façade,” comments Craig Simms, APM Team Leader (Southern) Metal Construction at Schüco. “Our architectural project manager provided technical support and guidance throughout the design process, including product selection. We also collaborated with Hale Brown on addressing the acoustic challenges posed by the proximity of the train line, providing test evidence from our Bielefeld facility to demonstrate compliance.
Terry describes the design development process as fast paced and highly collaborative, involving Hale Brown, Peter Dann, DE Group Contracting, and Glass Box Facades. “We held a number of workshops online with the whole team, which helped Glass Box develop its proposals for the glazing junctions,” says Terry. “We wanted the façade to be silicone jointed as much as possible, to emphasize the elegance of the vertical lines. Glass Box was able to work out a solution where all the vertical glass-to-glass junctions would be silicone jointed and only the horizontal joints had cover caps. The horizontal cover caps help to define and express the zig zag profile of the facade externally.”
Getting the details right
One of the first challenges for the team was to establish whether the existing structure could take the additional load of the new system. The existing – and poorly performing – structural glass façade was supported at each storey level by a perimeter steel ring beam, which zig zagged to match the profile of the façade. Due to the additional weight of the new facade, Peter Dann put forward a proposal for slender steel box section columns fixed to the internal face of the ring beams at each level to stiffen up the existing structure. Careful placement of the posts was critical to minimise their visual impact both internally and externally. “Peter Dann’s ability to evaluate and solve complex problems, particularly around integrating new systems with the existing building fabric, was essential in maintaining the integrity of the original structure while improving performance,” comments Dibley.
Another critical detail condition required the new curtain wall transoms to sit on top of the existing zig zag steel beams. However, it became apparent to the team that these were not all aligned all the way up the building. Glass Box Facades therefore had to undertake its own detailed site survey of the area to understand exactly where all the steels were and at what levels, and use this to prepare all its shop drawings.
Close collaboration between the architect and specialist subcontractor was also required for the new bay windows on the 5th floor and the sixth-floor façade. Precision surveys were undertaken to ensure that both of these elements aligned seamlessly with the vertical lines of the existing façade. On the sixth floor, Schüco FWS 50 curtain walling and ASE 60 sliding doors with design line interlock are combined to provide slim sight lines, good daylighting and panoramic views across the city. Rigorous detailing and fastidious installation by Glass Box Facades enabled the curtain walling and sliding doors to marry perfectly with the sharply angled, projecting metal cladding, achieving a refined and elegant look. Careful consideration also went into the detailing and execution of the dormer windows on the fifth floor. “We specified Schuco AWS 70 HI unit, incorporating angular thermally-broken corner profiles to achieve the ‘bay window’ aesthetic and meet thermal performance requirements,” says Dibley.
Site complications
A further challenge for the team was the proximity of an open-air section of London Underground’s District Line, which passes close by the site boundary. Glass Box Facades had to work closely with the main contractor to develop a logistics plan that did not impede the Tube network. “DE Group Contracting brought invaluable experience in managing the logistics, coordination, and execution of the refurbishment,” comments Dibley. “Their ability to handle the complexities of the construction process, including scheduling, procurement, and quality control, ensured that the project was delivered on time, within budget, and to the highest standard.”
The unique geometry of the zig zag façade also presented significant challenges – both in terms of scaffold access and the installation of the glass itself. “The scaffold had to be carefully designed to facilitate adjustment at each stage of the installation to ensure safe working conditions,” explains Dibley. “The glass was positioned using a self-erecting tower crane, which carefully manoeuvred through a narrow gap. Remarkably, all the glass was installed ahead of schedule and without any breakages.”
A job well done
The time spent by the design team attending collaborative workshops, discussing issues online and in person, presenting options and agreeing solutions is evident in the quality of the finished façades. For Terry, one of the team’s most impressive achievements was seamlessly installing the intricate zig zag curtain walling on a difficult site, close to an active railway line. “It all fitted together perfectly first time,” he says. “Glass Box prepared a great set of technical drawings, based on site surveys, that made the whole design development and approval process very simple. They really understood the importance of their drawings being coordinated with a very tricky and intricate existing site condition.”
For Simms, it is the successful integration of high-performance façade solutions with the architect’s unique design vision that stands out. “Close collaboration between the project team throughout the design and installation process has resulted in a building that is both aesthetically pleasing and highly functional,” he says.
Reflecting on the key role played by the architect, Dibley says, “Hale Brown brought vision and creativity to the process, ensuring that the refurbishment was not only functional but also aligned with the desired aesthetic and user experience. Their focus on design integrity and attention to detail ensured that the building’s character was enhanced while respecting its existing structure.”
Dibley also acknowledges the importance of Schüco on the project. “Their tailored solutions provided the design with state-of-the-art window and curtain walling systems that enhanced the building’s appearance, functionality, and environmental performance,” he comments. “Excellent technical support throughout the process ensured seamless integration of the Schüco systems, enabling the design team to achieve both aesthetic and performance goals.”
Contact Details
For more information, please call 01908 282111, email, or visit the Schüco website.
