Angel Building
The Angel Building is the re-invention of an unloved early 1980s commercial building located on one of London’s historic focal points where City Road and St John Street meet Pentonville Road and bustling Islington High Street.
Allford Hall Monaghan Morris’ brief was to devise a working environment that would exceed the latest office standards and create a memorable and inspiring place to work. The Angel Building provided the perfect opportunity for AHMM and Derwent London to build on their combined experience of delivering contemporary design, integrated with older architecture, to provide high quality office space with a strong identity.
Since inception, the Angel Building has undergone a radical transformation and now contains 23,116 m2 (248,835 ft2) of high specification office space, 1,239 m2 (13,345 ft2) of retail space, a remarkable atrium, a fine café and breathtaking views across London from its enormous roof terraces.
The original building was greatly at odds with its prominent location in a conservation area with many listed buildings in the locality. The poor massing, materiality and configuration of the existing external spaces had all contributed to its decline. Derwent London’s brief was to convert this into high quality Grade A office space that was flexible enough to appeal to a variety of tenants.
Planning Constraints and Opportunities
Local planning constraints meant Derwent London and AHMM were unable to build upwards by adding extra floors, so instead AHMM built inwards and outwards. The open courtyard in the centre of the building and large spaces to the perimeter suggested there were opportunities to increase floor area to finance the recladding and general reconfiguration without wholesale demolition.
AHMM created a five-storey grand top-lit atrium and a new fifth floor of office space and terraces by enclosing the forgotten service courtyard. The atrium serves as a grand entrance area, improves circulation and orientation and creates breakout areas, where trusses provide column-free spaces and sunken floor areas add height. The new fifth floor offices are set back from the building’s perimeter to conserve neighbours’ views and rights of light and have created large roof terraces, providing panoramic views across London
The front of the original building was located up to nine metres back from the roadside to make room for a road-widening scheme that never happened. The original building had three entrances, including one on the corner which was difficult to handle architecturally. The new Angel building was extended forward with a gently curving frontage regaining some of that space, while still leaving room for an improved public realm.
Early analysis of the existing building suggested it offered a number of opportunities that could save the client valuable time and money. Whilst the external cladding, services and internal finishes of the existing building had reached the end of their life, the reinforced concrete structure proved to be sufficiently robust and with suitable floor-to-floor heights (approximately 3.7m) implying that reuse was viable. Avoiding the demolition and disposal of the structure and construction of a new replacement resulted in immense CO2 savings, which contributes to the inherent sustainability of the development. The build-time for the project was also substantially reduced by reusing the structure, so overall cost savings were significant. To avoid costly and wasteful changes during construction, full size mock-ups for the most important elements of the building were produced early on in the design process. The careful consideration given to planning and delivery resulted in the project successfully being completed on time and on budget.
Materials
Because Derwent understands that a high quality working environment would attract good tenants, the client opted in favour of sophisticated, modern spaces and amenities. These included unexpected materials such as fair-faced concrete, timber with high quality finishes, marble terrazzo inspired by Italian design; sophisticated glass curtain walling and marble work surfaces. None of these decisions were merely at the whim of the architects. It was the result of a long series of design discussions and off-site, full scale model tests in which finishing techniques and spatial arrangements were built and checked out at real life size and scale.
Within the retained structure, the existing concrete was cleaned and sealed maintaining the simple, durable, low maintenance approach to finishes. A self-compacting concrete mix containing 36% of pulverised fuel ash replacement (PFA) was found to achieve the required architectural finish. The consistent quality of the finish is designed to a light, even grey with the tie holes and pour lines as the main features.
A simple palette of materials was used in the office floors to allow maximum flexibility to potential tenants: white plaster walls, sprayed plaster ceilings and metal raised floor tiles. Flooring and built-in furniture used Dinesen timber, all partition framing was black aluminium, and the columns were clad with lacquer panels.
To ensure the highest quality, AHMM and Getjar used full scale mock ups when testing the concrete finishes. The commitment of the whole team, including the client, was instrumental to the success of this key aspect of the project.
The unitised façade panels were prefabricated off-site complete with glazing, insulation and finishes to ensure a high degree of quality could be consistently maintained. The panels were then delivered to site and lifted into place by crate, at a rate of 16 panels per day, without the need for scaffolding. This speed of installation, combined with the early procurement of the façade package, enabled the building to become water tight in a short period which significantly reduced the overall programme.
