Cowan Court, Churchill College, Cambridge

Introduction

Churchill College, Cambridge, founded in 1958, was a pioneer in the radical expansion of university education and its ten brick and concrete courtyards, (or ‘courts’ to use the Cambridge term) were one of the first Brutalist buildings in the UK, designed in the 1960s by Sheppard Robson and now Grade II-listed. Its now-picturesque Brutalism is echoed in a new building for Churchill College, Cowan Court, designed by the practice 6a Architects and described by co-founder Thomas Emerson, as ‘the first wooden Brutalist building’. It shares much of the qualities of the Sheppard Robson buildings while quietly emphasising the differences.

Cowan Court was needed to house Churchill College’s growing undergraduate numbers, many of whom had to live offsite. It was also important that the building would centre the students in the campus, would be environmentally sound and fit within its historic surroundings.

The new court re-establishes the college as the centre of its social and academic community. It is a 68 room hall of residence and like the original halls it is a courtyard plan, three storeys wrapping around an inner open space, planted with birch trees which shelter an informal garden for students. As the architects explain: ‘Sustainability, accessibility, landscape and a new approach to communal and private space transform the raw sensuality of the brick and board-marked concrete courts of the original college into an innovative, contemporary, low-energy timber building’.

The student rooms, all en-suite, face the outer landscape and upper floors are reached via two staircases and a light-filled glazed cloister which runs around the courtyard side of each level, with deep window sills for students to sit and look out at the courtyard, and with kitchens at corners of each floor to encourage students to talk and socialise.

The rooms at ground level, designed to be suitable for disabled students or DDA-convertible, open onto a concrete plank pathway around the courtyard, which mimics those in the original college courtyards and covers a services channel.

Timber is used in all elements of the building, most dramatically in its cladding of dark weathered boards reclaimed from French railway carriages and reminiscent of the board-marked concrete of the original courts. The main structure is of glulam and cross-laminated timber (LVL); the large windows/ventilation panels to the study bedrooms, together with internal fittings, are of new European oak.

Will York, project structural engineer at Price & Myers, describes the structure:

‘Timber was an early choice; as well as its appearance and environmental credentials, a timber frame allowed the building to be constructed economically and quickly, on relatively shallow strip foundations rather than piling.

The building consists of four similar, but not identical, timber wings which form a square. One wing has a basement and two opposite corners contain concrete stair cores. As soon as each core was completed on site, timber framing started and proceeded clockwise round the building – allowing two teams to work concurrently.

The primary superstructure of each wing consists of glulam beams set out at 925mm centres, spanning about 6.5 metres between glulam columns on the outside wall and the internal corridor wall and cantilevering another 1.5 metres inwards to support the corridors and glazed courtyard façade. Using traditional beam-and-joist construction rather than CLT floor panels made it relatively easy to distribute services around the building without sacrificing space or ceiling height. The deeper beams also provide stiffness to the reasonably long-span floors and cantilevers and are an attractive warm element, exposed throughout the building.

The large primary beams are inherently resistant to fire; timber chars at a known rate and while a normal joist might burn away entirely in 40 minutes, the uncharred core of a larger beam retains a great deal of strength. By checking the fire case carefully, we were able to justify most beams for fire without any additional protection or any increase in size from the ordinary loading case. The secondary joists and columns are protected from fire by boarding.

The outside wall is cantilevered out at a different distance at each floor to create the distinctive curved and stepped external façade; the primary structure behind the curve is faceted in 3.7 metre long sections, from which the timber structure supporting the façade and windows is hung. The internal structural wall also doesn’t line up between floors, and changes direction often - but columns were carefully placed to line up between floors at every beam support without protruding from walls or requiring trimmers which would affect services distribution.’

The timber façade

The walls are clad with timber boards, reclaimed from the floors of French railway carriages and chosen to offer a natural warmth and softness to the outward and inward-facing facades, matching the colour and texture of the heavily planted surroundings. The boards, already weathered to a soft dark brown, blend harmoniously with the red/brown tones of Sheppard Robson’s original brickwork close by.

Each of the outward-facing facades has a concave curve in plan, like the entasis of a classical column, only reversed, and the upper floors are slightly jettied out from the floor below. The facades consist of bands of reclaimed timber boards, fixed vertically, and alternating with large new oak window/ventilation casings. At eaves level the top frieze of boards are routed into shallow ellipses to expose lighter-coloured timber beneath the weathered crust.

The inward-facing facades, looking onto the courtyard, are jettied but not curved; the ground floor is lined with panels of new vertical oak boards and matching new oak doors to the student rooms. The two floors above have the same reclaimed timber board cladding and a continuous band of new oak windows. The contrast between old and new accentuates the differences in colour and texture through age.

The window/ventilation units and reclaimed oak cladding were prefabricated into insulated cassette panels and at first and second floors these are fixed with steel brackets to an insulated softwood frame. This in turn is fixed back to glulam lintels and spreaders at floor levels. A typical cassette panel comprises seven 150mm wide, 30mm thick reclaimed boards fixed vertically to tapered battens and counterbattens; this in turn is fixed to 200 x 50mm softwood posts infilled with insulation. An inner 150 x 50mm insulated SFS frame is lined with plasterboard and secured to the glulam structural frame.

Internal timber elements

The structure of glulam beams and posts remain exposed in most areas, giving a rhythm and natural depth to the interior and echoing much of the expressive exposed structure of the original buildings.

The study bedrooms have generous proportions, at 20m² average size they are larger than those in most university residences. The structural glulam beams are exposed on the ceilings and the floors are laid with engineered oak boards. Each room has a triple-glazed picture window, framed in European oak and incorporating large openable ventilation panels on both sides. The windows are set above 600mm deep oak window sills, reflecting the depth of the insulation filling the walls.

Sustainability

The 68 students are housed in super-insulated, triple-glazed conditions which approach Passivhaus standards. The timber walls are highly insulated and significantly exceed current Building Regulation legislation. Dense roof insulation and coatings on the glazing delay solar radiation flow and prevent overheating.

Timber is used in almost every element of the building and all was PEFC and FSC sourced. All spaces have generous natural ventilation openings. The study bedrooms have integrated timber ventilation panels. Communal areas have motorised actuators to control summer temperatures and air quality. The windows can be opened for comfort and to suit individual needs. Electricity use is monitored room by room to keep users aware and prevent profligate use. Renewable energy is generated by solar panels and photovoltaic cells located on the roof.

Awards

RIBA East Award 2017

Civic Trust Award Commendation 2017

Cambridge Design and Construction Awards, Best New Large Building 2017

 

Completion Date:

2016

Building Type:

Student accommodation

Location:

Cambridge

Client:

Churchill College

Architect:

6a Architects

Structural Engineer:

Price & Myers

Environmental Engineer:

Max Fordham

Façade Consultant:

Harry Montresor Partnership

Main Contractor:

SDC Builders Ltd

Landscape:

Jonathan Cook Landscape Architects

Timber Structure:

B&K Structures Ltd

Specialist Engineer:

Engenuiti

Window Joinery:

Flexwood

New Cladding Supplier:

Bartram Timber Ltd

Reclaimed Cladding Supplier:

BCA Materiaux Anciens

Timber Elements:

structure, cladding, doors, windows, floors

Timber Species:

European whitewood spruce, new and reclaimed oak, tulipwood, beech

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