Chris Rogers writer on architecture and visual culture

The Angel Building

New architecture need not mean a new building. Or at least, not a completely new one. As another decade turns, architecture is turning too. After many years of rumbling concern, a real appreciation of the impact on resource consumption of the constant cycle of demolition and erection is beginning to be seen in developmental projects across the world. Whereas new build would have been the automatic choice even five years ago, re-modelling and re-building is now an entirely viable alternative that is actually being selected in many instances.

This approach goes well beyond simple refurbishment or conversion, involving instead the return of a building to its skeleton state followed by complete restructuring.

And although retaining existing materials and the energy embodied in their extraction, fabrication and assembly is a positive goal in itself, it can also result in the retention of building elements with aesthetic value. At 107 Cheapside in the City of London, for example, John Robertson Architects have added a new glazed rear to an existing 1950s building, retaining its elegant principal facade of Portland stone with only subtle modifications. Excellent modern office accommodation is provided at reduced cost whilst also preserving a decent contributor to the Square Mile’s post-war processional route.

Elsewhere in London, developer Derwent and architects Allford Hall Monaghan Morris (AHMM) have made a speciality of this method, creating a range of high-quality, individual spaces through the re-versioning of existing buildings.

Their newest venture together, the Angel Building in Islington, extends these principles and both parties’ involvement considerably further and is a valuable example of the trend to dissect.

The starting point was the existing building. The Angel Centre dated from around 1980 and was by prolific commercial concern Elsom Pack and Roberts, now EPR. Built for London Merchant Securities Group, whose founder Max Rayne was a close friend of EPR partner Cecil Elsom, the Centre loomed over the junction of Pentonville Road and St John Street. Set back from the road and further hidden behind extensive greenery, rigid – even ruthless – geometry was sheathed in flush dark glazing between mullions of polished salmon-coloured granite to form a rather glowering presence.

With a view to establishing a major office rental opportunity in a part of London that lies conveniently mid-way between the City and the West End, Derwent commissioned AHMM to reconstruct the Angel Centre completely to form around 23,000 square metres of attractive, flexible letting space.

A quadrangle on plan, with four staircases at the corners of a central courtyard, the Centre's reinforced concrete frame was sound and was retained, as were the staircases. The remaining interiors and services were stripped out completely, and the facade removed.

This led to consideration of the building’s footprint on its plot, its relationship to the streets surrounding it and the client’s brief. Two major alterations resulted.

First and most visible is the considerable extension of the St John Street building line to the east and the addition of a new concave facade. A planners’ requirement to leave a clear sight line across this frontage from ground level toward the dome of a Vicwardian building on the adjacent corner limited further growth, but this elevation does now align with an adjacent building and more closely follow the street layout. The south side of the building was also extended.

Secondly, the space previously occupied by the courtyard was turned into a full-height atrium-cum-lobby and covered over with an ethylene tetrafluoroethylene (ETFE) pillow roof. Reached via the main entrance in St John Street, this forms the heart of the new Angel Building. It is central to the concept of the building and the experience of using it, as will be seen.

Retention of the frame drove the floor heights of the new building, which vary slightly due to irregularities present in the original structure but are about three metres. Internal space is defined by large glazed panels with fritted spandrels, and is arranged on a three metre planning grid.

Crucially for AHMM’s vision of more open and natural working conditions, a raised floor contains almost all elements of the forced ventilation system. Warmed air is pushed gently through vents in the floor, rises, hits the exposed concrete ceiling and moves toward the edges of the spaces, from where it is extracted by the only other mechanical portion of the process. This removes the need for suspended ceilings, takes advantage of the thermal mass of the concrete, cuts capital and revenue costs and uses the large ceiling height to make a less oppressive space. Comfort is also improved by reducing the artificial atmosphere typical of office buildings and eliminating the considerable downdrafts of a full conditioning system.

Opening glazing in the new exterior cladding with fritting for shading is also a contributory feature to this more natural approach. Other measures include rainwater harvesting, waterless urinals, bio-mass boilers and a new generation of Otis lifts which consume less power in the first place but also employ regenerative braking, which recovers energy ‘lost’ in deceleration in a similar way to the current breed of Tube trains.

AHMM believe their overall approach will lead to more and more efficient and sustainable buildings with taller floors unencumbered by added mechanical systems. Associate director Philip Turner, touring the building with the author, compares this to traditional buildings; architects usually “introduce as many components as are needed to fulfil flexibility and plan to replace them when they fail, whereas we eliminated them”.

Amenity space on upper floors comprises two large open-air terraces, with access split between different tenanted areas, and the hard and soft landscaping to St John Street has been opened up, though most of the mature trees from the previous scheme have been saved. This is in truth the least successful part of the rebirth. The building’s location does not necessarily lend itself to meaningful public threshold improvements, and the extension of the building line and new paving is a little corporate in feel.

But it is the atrium with the new Angel Building that shows AHMM’s true colours.

A low, compressive entrance from St John Street leads to a wide passage with unfussy recessed benches on each side. These – wooden, downlit and with more lighting below – effectively float, and highlight the first view of the panels of fair-faced concrete that are the internal finish of the building. The warmth and coolness of each offers a contrast that is surprisingly calming and effective.

This passage then opens dramatically into a vast, six-storey-high space that is the atrium proper, formed from exposed concrete panels, columns and beams and internal glazing units. The distinctive roof structure is of deep cruciform in-situ concrete beams, spaced to match the upstands of the atrium walls. New columns are also of concrete, with existing examples overclad to match.

A sunken meeting place furnished with primary-coloured sofas and recalling a business class airport lounge lies to one side and is balanced by the Angel Café to the other. Two new lift cores flank this central space. Ahead and one floor above is a large break-out area stepped out from the office floors like an open drawer, a kind of internal terrace in response to those externally. Smaller single- and double-height open galleries at the sides of the atrium, reached via the office floors, have coloured chairs selected by the architects.

A mesmerizingly precise floor of grey terrazzo – marble chips in cement, allowed to harden and then polished – inset with slugs of solid white marble on a tight, almost textile, grid reflects in miniature the pattern described in the atrium walls and the roof.

The heroic scale of the atrium with its loud-and-clear echoes of Louis Kahn are a powerful and commanding statement and in fact hide some complex engineering required to knit together old and new, but for AHMM the goal was to create a civilised space at the centre the building. Director Simon Allford, also on the tour, points out how the typical placement of circulation core immediately inside entrance so as maximise rentable floor space was avoided, with Derwent’s consent: “We wanted to not have lifts right there, but bring people deep in”.

This works, and works well. A neutral but not insipid colour scheme formed from the concrete, the black framing of the internal glazing units and the furnishings is the background. People walking along the lobby, across the first-floor terrace and in and out of the galleries set up at least three axes of movement on several tiers that bring a genuine sense of life to a space that could seem cold and dead. By this means and by connecting it to the outside, the atrium is enlivened and made welcoming, very different from the expected sterile white box and more akin to the foyer of a museum or art gallery. The boundaries and definitions of private and public architecture are productively blurred.

Materials selection and execution was another vital aspect of this decision. The floor has already been mentioned. The stated inspiration is Carlo Scarpa’s rougher, artisanal example in his magical, jewel box of a shop for Olivetti in Venice, finished in 1958, but here a more mathematical form is used. It is carried confidently through an exquisite pair of staircases leading to the first floor terrace, complete with fluidly radiused tread and riser junctions and beautiful stainless steel handrails, and into the lift cars. Sheathed in milky glass with buttons delightfully arranged, a bespoke solution, Allford describes how these cars home to ground each morning and quietly wait for arriving workers with their doors open. It’s a good example of AHMM’s careful approach to building an undemonstrative but humane and uplifting environment; rather than a steel box, “this ‘room’ is presented, which you step into”, he explains.

Additional details, such as the discreet 'makers' mark' text affixed to one wall and curved glass connections between the revolving doors and their glass panel surrounds only reinforce this impression, as do the installed contemporary art pieces including Ian McChesney’s carbon fibre extrusion. Overcladding of columns is surprisingly hard to get right, but AHMM manage it well.

Although the firm has found an equilibrium between re-use and new build across its work, the Angel Building develops the specific approach and architectural language originated at the Johnson Building in Hatton Garden. On a smaller scale, that project’s mix and match of old and new, use of exposed concrete and even its particular layout of entrance passage leading to atrium nevertheless provided a blueprint which has now been worked up into the much larger but equally assured scheme at the Angel. It is perhaps a Lotus to Islington’s Bentley.

In the letting brochure for the Angel Building AHMM cite Mies van der Rohe as one influence, expressly for the pacing of the new facade cladding, though it's not hard to detect reflections of his craftsmanly love of materials too. Mies trained as a stonecutter under his father and had an arts and craft education. This is seen in the crisp metal pieces and richly coloured polished stone slabs, like slices of jelly, present in the Barcelona pavilion, Seagram building and Tugendhat house, and referenced in the new building. The Angel Building’s cruciform atrium roof, meanwhile, has a clear precedent in Kahn’s Yale Center for British Art in New Haven.

The integrity and quality of the Angel Building are evident in walking around it and hearing how it was created. Observing the movement in the atrium brings a smile to the face as this Escher-like hive lives. The emphasis on ecological efficiency, usability and generosity has already seen Cancer Research UK take a large part of the building during final construction, and AHMM worked to give them their own reception and link some floors.

The architecture is simple, resonant and muscular, and it breathes. As Allford says, “Why squeeze a building till it squeaks?”

Angel Bldg - orig
Angel Bldg - orig bldg mod

The Angel Centre before its remodelling; a simple rectangle with a central courtyard (getmapping.com; AHMM/Derwent)

Angel Bldg - new plan

Ground floor plan of the reborn Angel Building, to the same orientation. The extensions to the east (with concave facade) and south and infilled courtyard can be seen. Just visible at this scale on both images are the original four stairwells (AHMM/Derwent)

Angel Bldg - atrium (AHMM)
Angel Bldg - cross fl (mod)
Angel Bldg - across lift landings
Angel Bldg - down

Views of, across and down into the new atrium in the reconstructed Angel Building, with Ian McChesney's carbon seat/sculpture prominent in the top image. The Kahnian treatment of the roof and the wall panels, with tie-rod holes left visible, bring great interest. Note the first floor internal terrace to the left of the bottom picture, with stair (top image - AHMM)

Angel Bldg - loo - mod
Angel Bldg - lift - mod

Lift and toilet signage details

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