Bishop Edward King Chapel, Cuddesdon, Oxfordshire

Introduction

Ripon Theological College is an Anglican seminary and its collegiate buildings, built of warm Cotswold stone by G E Street in the 1850s, stand amid rolling fields and ancient trees in rural Oxfordshire.  In these idyllic surroundings, in a clearing flanked by a huge copper beech dating from 1710, is the new Bishop Edward King Chapel, designed by Niall McLaughlin Architects. The community had recently been joined by the nuns of a small religious order, the Community of St John Baptist, and the new chapel was built to serve the two communities.

The chapel is an elliptical drum of Clipsham stone; McLaughlin cites churches by Rudolf Schwarz and Peter Zumthor as inspiration for his use of the ellipse. The walls are of smooth ashlar stone at lower levels, a mid level of alternating smooth and rough coursed stone and an upper level, a deep and delicate clerestory of glass with fine stone mullions between. A timber entrance door links the chapel to a separate single-storey sacristy, toilets and storage.

The internal volume is also elliptical in plan, a serene and light-filled place of worship with the altar and a solid oak lectern semi-enclosed in an inner ellipse created by a series of lofty glulam arches which rise and curve to create an open diagrid above it. The use of an ellipse, a geometrical figure whith two centres, allows worship to focus on either the rituals of the eucharist or on the spoken word: the altar is placed at one curved end, the lectern on the other. The seating plan is 'antiphonal' with two banks of congregation facing each other on fixed benches made of ash.

The space between the elliptical enclosure of arches and the external wall forms an ambulatory. As the architect explains; ‘The movement inherent in the geometry is expressed in the chapel through the perimeter ambulatory. It is possible to walk around the chapel, looking into the brighter space in the centre. The sense of looking into an illuminated clearing goes back to the earliest churches. We made a clearing to gather in the light.’

Around the ambulatory are a series of single-storey niches which extend beyond the walls. One houses a wedge shaped oriel window, another the space for the tabernacle and the largest is a prayer room for the sisters to recite their offices, a top-lit space with a carefully framed view towards the altar.

 

The wall and roof structure

The structure can be divided into two essentially independent and self-supporting parts; firstly the external wall, secondly the roof structure, glulam columns and lattice diagrid.

The ellipsis of the external wall is inherently a very strong shape, a factor which allowed the wall to be more than 10 metres high without requiring restraint at the top. Concrete was chosen for the wall structure as it worked well, in terms of movement, with the outer stone leaf and the internal finish of lime plaster. An in-situ concrete wall was considered but the elliptical formwork costs were prohibitive; instead the wall was constructed of hollow concrete blocks with reinforced concrete infill.

The roof structure consists of a series of inverted timber trusses lined with staggered 6mm birch ply panels and prefabricated into panels which could be craned into place on site.

The apexes of the inverted trusses rest on a 150 x 80mm RHS which runs along the tops of the curved diagrid of glulam beams and columns. At the curved ends of the ellipse the trusses fan out, supported at the ends of the RHS. With this support only lateral restraint was required where the roof trusses meet the glulam columns at the top of the clerestory mullions.

 

The internal glulam structure

Glulam was chosen for the internal timber structure for its ability to create elegant curved columns and beams.  A series of portalised columns, set in an ellipse on plan, curve inwards into the elegant open diagrid which arched over the centre of the chapel. Single 60mm thick glulam columns (tapering from 300 to 430mm) run at the curved ends of the ellipse. The other columns are each formed of three separate glulam members; two 60mm thick outer members tapering from 300 to 560mm and a central 60mm thick member tapering from 200 to 440mm, all screwed together by timber fillets, filled and plugged. As they rise upwards, the outer members curve inwards in different directions, connecting to adjacent glulam members to form the diagrid, while the central member curves upwards in the opposite direction to meet the clerestory mullions.

The spruce glulam components, produced by Cowley Timberwork, were CNC machined to profile and to create their concealed connections, then cut and finger jointed to produce the curved haunches of the portalised columns. A channel was cut into the top of the glulam rafter section to house and conceal cables and lights. The glulam structure was fabricated off-site and the individual elements were then craned and bolted into place. This allowed for the very precise machining required to achieve the sweeping curves and concealed connections and fabricating components to +0/-1mm tolerance.

One of the greatest challenges was to achieve the ideal of a very slender glulam structure with the members almost seamlessly passing across each other and only barely touching the roof they support. The key to this was the connection of the glulam members. The connection had to accommodate lighting cables suspended from the central joint and the steelwork – bolts and screws - had to be concealed while still providing sufficient strength to support the roof. All these requirements had to fit within the 60mm thickness of the glulam members. M12 steel rods, resin-bonded into the ends of the glulam with couplers and Allen head bolts, were used to bolt the fabricated steel connection blocks together. This was all hidden within the 60mm thickness while providing a moment and shear connection between all four glulam members.

 

Finishes

The materials of the chapel interior – stone, lime plaster, ash furniture, oak doors and spruce glulam columns share similar natural colours;

the glulam was treated with a two-part stain, giving it a light, white-washed appearance. The restrained pallette allows the play of light from the glass clerestory to dominate the interior.

 

The Bell Tower

The 13.5 metre high bell tower is a free standing timber structure consisting of two diamond-shaped, glulam oak columns each profiled from 250 x 800mm sections. They cantilever from the concrete foundations. Stainless steel rods were resin fixed into the base of the oak and bolted to a stainless steel plate cast into the foundations. The columns are reasonably deep and slender in section. They cantilever in their deep direction but they work together as a cantilever Vierendeel truss in their narrow direction.

Completion Date:

February 2013

Year Published:

November 2013

Building Type:

Chapel

Location:

Cuddesdon, Oxfordshire

Owner/Client:

Ripon College and Community of St John Baptist

Architect:

Niall McLaughlin Architects

Structural Engineer:

Price & Myers

Main Contractor:

Beard Construction

Timber Roof and Glulam Structure:

Cowley Timberwork

Timber Furniture:

Westside Design

Timber Elements:

Bell tower structure, roof and internal structure, external and internal doors and fitted furniture

Timber Species:

FSC certified spruce, European oak, ash

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