Grimshaw: New Academic Building, London School of Economics & Political Science

Photo: EAG/Granville Davies

Aluminium windows and curtain walling are used to skilful effect at the LSE’s New Academic Building.

In the spring of 2005, Grimshaw was commissioned by the London School of Economics & Political Science to design a new flagship academic facility. The project involved the extensive remodelling of an existing Edwardian building, originally constructed in 1912 to house the Public Trustees Office. Situated at the northernmost point of the university’s central London campus, and bridging between the urban environment of Kingsway and the open space of Lincoln’s Inn Fields, the recently completed £46m scheme provides state-of-the-art academic, social, and departmental spaces over ten floors.

For the architect, one of the main challenges was to find subtle ways of expressing the ethos of a modern, world-class educational institution through a relatively ‘closed’ Edwardian office building, without undermining its Beaux Arts context. Key to this approach has been the skilful remodelling of the central core, with new floor plates arranged around an atrium and a six-storey glazed lightwell. Added to this, the existing street elevations have been reworked to include taller windows with deep aluminium reveals, and a 128 square metre glass pavilion has been constructed at roof level.

Uniting each of these careful interventions is the use of Schüco aluminium curtain walling and window systems. The new fenestration provides not only slim sightlines and good levels of acoustic performance (essential, given the building’s prominent location on Kingsway), but it also contributes significantly to meeting a ten per cent improvement on Part L of the Building Regulations (2002) for the new facades, as part of the scheme’s overall BREEAM Excellent rating.

The 12,700 square metre building comprises eight storeys above ground and two below. The teaching and larger social spaces are oriented toward the lower levels and organised around a central atrium space. The academic departmental spaces are arranged in a U-shape around the atrium lightwell on the upper levels. The lightwell itself is formed from Schüco’s Skyline C65 SG (structural glazing) unitised aluminium curtain walling system. The 3.5 metre high double-glazed units run floor-to-floor, eschewing the need for spandrel panels and maximising the amount of daylight entering the building. Solar shading is not used in the lightwell as it is north-facing.

While more than 50 per cent of the building’s existing fabric was retained, a significant portion of the inner structure was removed and replaced with new column-free floors suspended from a steel truss at eighth floor level. The steel truss is supported by a pair of columns which straddle the primary 400-seat lecture theatre located directly beneath the atrium.

Forming the nucleus of the building, the atrium is a light-filled, triple-height space with gallery levels to all sides linked by skeletal scissor stairs. Referred to as the ‘sounding board’, the atrium’s timber floor folds down to provide access to the lower-ground lecture halls and function spaces, before sweeping upwards to the glazed atrium roof and framing the two mezzanine gallery levels. The roof is supported by a series of steel bow-string trusses. The lightweight structure ensures a strong visual connection between the atrium and the upper floors, as well as good levels of daylight. The width of the glass roof panels (typically around 1000mm) was kept to a minimum to reduce deflection and to ensure easy integration with the lightwell facade module above.

On the street elevations, the architect has introduced a number of subtle interventions designed to open up the existing facades and articulate the contemporary remodelling within. The entrances on the east and west sides of the building are connected via an internal street, allowing views right through the ground floor from Kingsway to Lincoln’s Inn Fields beyond. The existing entrance off Lincoln’s Inn Fields has been enlarged to accommodate the needs and scale of the New Academic Building, while simultaneously respecting the retained fabric. The window openings on either side of the two entrances have been extended down to the ground to produce a colonnade through which people can pass. The glazing is set back behind the colonnade, away from direct sunlight. This diminishes the reflectivity of the glass, allowing unobstructed views into the building. Increased transparency also results from the introduction of double-height windows along Sardinia Street to the south and new shop fronts located at the corners of the building. The latter are formed by merging the original windows together and extending the openings down to the ground.

The original fenestration comprised single-glazed, multi-panelled timber sash windows throughout. These have been replaced with side-hung, double-glazed Schüco Royal S 75BS.HI aluminum windows. Associate architect Andrew Milward-Bason says, ‘We wanted to achieve a ten per cent improvement on Part L (2002) as part of the environmental aspirations for the project, while also retaining the ability for building occupants to control their environment by opening the windows. This was especially important as the facades are lined with cellular spaces including classrooms and academic offices.’

Located at roof level is a steel-framed single-storey pavilion housing the executive meeting rooms and social areas. Conceived as an outward-looking space, the slim profile Schüco FW50+ aluminium curtain wall facades capitalise on the surrounding views over Lincoln’s Inn Fields, the City, and Covent Garden.

Facade design

Grimshaw’s decision to use Schüco aluminium curtain walling and windows for the atrium lightwell, existing facades and rooftop pavilion was taken for reasons of aesthetics, performance, cost and familiarity – the systems having been successfully used on a range of previous projects. The architect undertook the detail design of the lightwell and pavilion in collaboration with Schüco’s technical team and specialist cladding contractor English Architectural Glazing. EAG was also responsible for producing shop drawings, fabrication and on-site installation.

Lightwell specification

Schüco’s Skyline C65 SG (structural glazing) aluminium unitised curtain walling system was specified for the six-storey lightwell in order to create a smooth, flush-fitting glass envelope that would maximise natural daylight and views out. The appearance of structural glazing is achieved by using slim 65mm profiles that are only visible from inside the building. From the outside, only the glazing panels and silicone joints are visible. Transoms were added with capping beads to create a ‘stack of halos’ rising up the lightwell.

Designed to correspond with the three-metre office partition module, the 21.5 metre high facades are organised on a one-metre grid. This results in three panels per office, with the outer bays relating to the furniture zones and the central one left clear. The factory-assembled frames are formed from polyester powder-coated grey (RAL 9006) aluminium mullion and transom sections (screwed and glued together), with a 6mm heat-soaked toughened outer pane (incorporating a high performance coating to the inner face), an 18mm cavity, and a 10mm heat-soaked toughened inner pane. Some of the aluminium frames incorporate 80mm thick insulated aluminium composite panels to conceal service areas located directly behind the facades. The mullions are lined with acoustic insulation to minimise cross-talk between the internal partitions.

Measuring approximately 3.5x1m the frames are fixed to floor brackets bolted to the top of the concrete slabs. A 25mm diameter steel pin projecting from the top of each floor bracket corresponds to a hole in an L-shaped bracket, extending from the top of the frame and providing a quick and easy fixing. The units are fixed to each other horizontally and vertically using a system of concealed tongue-and-groove connectors located on the top, bottom and sides of the units. The recessed joints between the frames are sealed and weatherproofed using epdm gaskets and UV-resistant silicone sealant. The facades areterminated above the atrium roof and at parapet level using pressed aluminium cill flashings and copings.

The three lightwell facades were installed over a period of eight weeks. The frames were delivered to site in stillages, with the double-glazed units and/or aluminium composite panels already installed. The stillages were lifted by crane from the lorry to the floor plates surrounding the lightwell. A lightweight Valla crane was used to lift and position the frames onto the floor brackets below. Silicone sealant was applied between the frames by abseiling site installers.

Pavilion specification

Schüco’s FW50+ aluminum curtain walling system was specified for the rooftop pavilion for its slim sightlines, structural stability and the ease with which it could be adapted and integrated with other materials. Planned around a 1.8m grid, the thermally-broken system comprises 50x150mm mullions and transoms infilled with double-glazed units. The glazing comprises an outer leaf of 6mm heat-soaked toughened glazing with a high performance coating to the inner face, a 16mm air gap, and an 8.8mm clear laminated inner leaf. According to the architect, the average U-value for the curtain walls is 1.87 Wm2K.

At floor level the mullions are bolted to a series of spigots (concealed within the aluminium sections), which are fixed down to the concrete upstand. A similar detail is used at eaves/parapet level where the spigots are fixed to steel brackets bolted back to the steel roof structure.

Externally, the transoms are fitted with square-profile cover caps, while the mullions employ structurally-bonded silicone between the glass panels. Mitred silicone joints provide crisp glass-to-glass connections at the corners of the enclosure. In common with the lightwell facade, this gives the curtain walling a seamless appearance, reminiscent of structural glazing. Solar shading is provided by a simple galvanised steel canopy extending from the insulated aluminium fascia above the curtain walling.

Window specification

Schüco’s Royal S 75BS.HI window system was chosen for the existing facades due to its ability to combine good thermal and acoustic properties – in the order of 1.1 W/m2K at centre pane and up to Rw 47dB (depending on frequency) – with a minimal frame width (75mm). Slim sightlines were also important for maximising daylight and transparency. The system was specified with a 100mm opening restrictor and key operated override (for maintenance access), allowing the windows to be cleaned from within, rather than using a cherry picker.

The metallic grey polyester powder-coated, side-hung aluminium window units comprise an outer pane of 6mm Suncool HP Neutral 70/40 toughened heat-soaked glass, a 16mm argon-filled cavity, and then a 7/13mm laminated inner pane with an Optilam Phon acoustic interlayer. The thickness of the inner pane was varied according to internal acoustic demands and external noise levels. Measured from the centre pane, the window’s U-value is 1.1W/m2k.

The ground floor window openings are framed by deep aluminium reveals, designed to conceal the areas where the existing stonework was cut to accommodate the new fenestration. Responding to the building’s two-storey band of rusticated stonework, this detail is carried through to the first floor, resulting in a consistent and uniform appearance.

Project team

Architect: Grimshaw; project team: Colin Ashton, Ingrid Bille, Andrew Milward-Bason, Alex Catterall, Tom Van Hoffelen, Eamonn Mohieldean, Vito Gramegna, Nigel Hetherington, Peter Knoerr, Michaela Kroll, Ursula Pfaffermayr, Oliver Pike, Hannah Sargent, Neven Sidor, Judith Wilke; structure: Alan Baxter & Associates; services: Battle McCarthy; qs: Davis Langdon; acoustics: Arup Acoustics; fire engineering: Buro Happold; urban design: Space Syntax; landscaping: Randell Siddeley; main contractor: Geoffrey Osborne; client: London School of Economics & Political Science.

Selected subcontractors and suppliers

Schüco Skyline C65 SG & FW50+ aluminium curtain walling: English Architectural Glazing (EAG); Schüco Royal S 75BS.HI aluminium windows, glazing: Colorminimum; facade stonework: PAYE Stone Restorations; lifts, travelators: Kone; smoke vents: Colt; drylining: Pan Interiors; structural steel, staircases: Bourne Steel; roofing, mansards: T&P lead Roofing; signage: Model Signs.