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Caruso St John, Organ loft at Canterbury Cathedral

A commission for an organ loft sounds like the perfect project-in-a-nutshell: an exercise in creating architecture in miniature, conjuring visions of a St Jerome’s study-like eyrie. Talking about Caruso St John’s new organ loft in Canterbury Cathedral, practice co-founder Peter St John does indeed refer to it as ‘a little building’ but points out that, having no roof, it’s more platform than house or aedicule.

Unlike other small structures around the cathedral, such as pulpits or tombs, it’s not designed for display. Part of a project to improve the organ’s acoustics, this was a commission for something that, to invert the old saying about children, should be heard and not seen. Or, at least, should not draw attention to itself.

This requirement stemmed in the main from the sensitivity of the context, a Grade I-listed World Heritage Site. That the loft has been more than six years in the making since the original 2014 competition whereby Caruso St John’s design was jointly selected, leading to a run-off contest at the beginning of 2016, gives an indication of the delicacy of this relatively small design project.

The competition had followed a decision not to go ahead with an earlier design proposal for the loft by engineers AKT II. An aside by director of works Mark Sharratt reveals that, for many stakeholders, putting a new structure in the cathedral has been ‘Marmite’.

The repositioning of the organ console corrects a longstanding fault in the instrument’s arrangements. Unlike in many churches, where a grand organ sits on high as part of the decorative schema, at Canterbury the original installation seems to have been more an exercise in concealment. Two sets of pipes were sited in galleries above the quire’s south and north aisles behind stone arcades.

The organist was seated perpendicular to these at some distance on a bridge above the quire screen, the key sightline between organist and choirmaster in the stalls half-obscured by a stone balustrade. Over the years, the twin arrangement’s sound became unbalanced, so the project’s aim has been to rebalance and expand the pipeworks’ intonation and at the same time improve the organist’s position.

Acoustic consultant Puetz checked the acoustics of the cathedral by flooding it with white noise and measuring the reverberation levels. It identified two positions above the north and south side-aisles that offered acoustic ‘sweet spots’ for an organist relative to the two sets of pipes, while being much closer to the choir. This indicated that a new organ loft needed to be constructed in one of the aisles up against the back of the choir stalls, raising the organist up to allow visual connection down to the choir while minimising visual distraction from the high altar.

As the south aisle has a much higher footfall, a position in the north aisle was chosen. It is in one of the oldest parts of the building, dating to the 12th century and sitting over a vaulted crypt, up a flight of steps from the spot where Canterbury’s most famous archbishop, Thomas à Becket, was murdered in 1170.

Looking up and down the cathedral from this point, its highly varied floor plane and irregular topography becomes apparent. To the east, steps rise up behind the high altar, while to the west, a flight of steps drops more than 2m to the nave, the grid of which shifts noticeably off to the left, giving the whole interior a markedly organic feel, akin to a landscape.

Even calling it a grid is to attribute a symmetrical precision to the plan that’s not really present. As St John observes, Gothic architecture by its nature ‘absorbs asymmetry and variation’ – a consequence of structures being built by a multitude of masons over centuries. He refers to the ‘coral reef of scales’ to be found in the Gothic of the Cathedral – with objects and additions such as pulpits and font-covers composed of Gothic-detailed elements in incremental miniature that echo and extend the language of the building.

For many of the project’s stakeholders, putting a new structure in the cathedral has been ‘Marmite’

‘We wanted to make a little building that related to the Gothic too: very vertical and asymmetric,’ he says. A certain Gothic verticality is achieved in any case by the 3.5m height of the stand required to allow a seated organist to see over the choir stalls, while the dimensions of its small footprint in plan are generated by the size of the console, organist’s seat, some storage space and the head of a small spiral stair, deemed a ‘work-stair’ and thus allowed to have a 700mm width of tread.

The loft’s visual massing was tested from different viewpoints during the design process with a 1:1 scaffolding and plywood prototype. Sitting above a 12th century vault and directly on Medieval flagstones, the loft structure needed to be as light as possible and to spread its load, while remaining self-effacing visually, interfering minimally with the surrounding architecture.

The decision, therefore, to fabricate the stand from steel rather than timber seems a good one: the slenderest of zinc-coated, blackened steel elements, like spindly legs, meet a thicker-membered base which distributes the load around eight feet. The dark finish keeps it visually distinct from the pallor of the surrounding Caen stone arches, while the material finds precedents in the metal railings, grilles and cast-iron fretwork of tombs. A reference, too, can be made to the early steel structures of 19th century structural rationalism, in part inspired by the Gothic.

The delicacy of the steel frame is accentuated by its being constructed of bespoke, squared-off 50mm sections, rather than standard, round-cornered extrusions. Their precision is further enhanced by seamless fixing to one another without visible welds. This makes the whole read as a continuous abstracted framework, like a kind of attenuated vertical instrument or armature. Caruso St John says a conceptual reference was Alberto Giacometti’s 1932 sculpture The Palace at 4am, in which a series of objects float in skeletal frames.

Indeed, a curving backbone-like element in the sculpture finds a faint echo in the vertical spiral of the loft’s steel stair and its handrail. The positioning of the stair also serves to breaks any implied symmetry in the loft’s stand. It is more subtly undermined by the irregularly spaced vertical ‘legs’, which shuffle out-of-sync with the more regularly spaced ‘feet’. One vertical steel is also thicker than the others, enabling it to act as a conduit for services to the console above.

It is no warmly haptic object, celebrating its making, but a smooth, sleek, background one, sitting quietly in place

While the whole was designed as an independent structure and engineered by Price & Myers as such, in practice a perceptible vibration when the organist played required a tie to be secured into the join of a neighbouring column at high level. This slightly undermines the concept of the loft as a free-standing piece of furniture, but assuages any lingering doubts one has when standing on top of what feels akin to a very tall bureau.

The stair, while half-contained in the main steel frame, sits half-proud of it to the right, in a vertical secondary steel frame enclosed in a dark timber box, a small flush door opening outwards at its foot.

‘Our model was the discreet pantry doors opening out into country house dining rooms,’ says Caruso St John associate Will Pirkis, who led the project.

 

This vertical stair enclosure complements the horizontal box-like form of the console lying like a dark muniments chest above. Both are fabricated of cross-laminated timber faced in American black walnut veneer. This is tipped in solid walnut at edges and around elements likely to suffer wear, such as the door’s lock and its neatly turned little knob.

Walnut was selected to match the colour of the oak of the choir stalls, darkened through centuries of use, but also for its ‘tracery-like’ grain. The intention perhaps was to add a decorative aspect to warm up the loft’s otherwise plain forms, and to soften the contrast with the highly decorated surrounding surfaces. But the result, in fact, speaks more of luxe hotels.

Arriving up the spiral stair, the ‘loft’ proves to be a low-walled enclosure, with the console sitting to the left between two slots of storage. Constructed separately, its position was adjusted forward on installation, witness – as is an organist’s cup of tea left on the floor due to there being no handy shelf – to the usual teething problems of any architect-designed environment meeting messy reality.

The precision and skill of the construction by fabricator Millimetre of Brighton (which also made the frame) is undoubted, with seamless connections achieved between panels. The look-no-hands precision makes this loft a beautiful yet deliberately untactile object, its noli me tangere vibe intentionally deflecting attention or excess study of it as an object, one’s glance looking through – or glancing off – its surfaces.

It is no warmly haptic object, celebrating its making, but a smooth, sleek, background one, sitting quietly in place, oddly mute in contrast to the acoustic function it supports. It’s a gently surreal one too, in line perhaps with its Giacometti-inspired roots, slightly eerie on passing, its function not immediately clear, even a little sinister.

 

Client’s view

The Quire Organ is unusual for its fully concealed location high in the quire triforia.While the sound of the instrument can readily be heard and indeed felt in the vibrations of the fabric, it is completely decoupled from the usual focal point of a visible console, forcing a disconnect between organist, instrument, choir and congregation.

Acoustic testing, coupled with assessments of physical and visual impact on the fabric, found the best location for the console to be in the north quire aisle.Making use of a fibre-optic control system for the organ stops, a new organ loft could be designed for this location. Following a limited invited competition, Caruso St John was selected to deliver the project. 

A complex series of statutory consents were required under the Care of Cathedral’s Measure. This required a close working relationship with the cathedral architect, engineer, archaeologist and the Cathedral Fabric Advisory Committee. Successfully navigating the risk of ‘design by committee’, the architect and contractor have delivered on a strong concept, with a carefully crafted new addition to the cathedral’s rich architecture.

Jo Deeming, partner, Purcell, and Surveyor to the Fabric of Canterbury Cathedral

 

Engineer’s view

The devil is in the detail, and there are plenty of hidden complexities to belie the apparent simplicity of this amazing project. The loft sits on delicate historic fabric – stone tiles spanning two historic service trenches built on the ancient, vaulted stone ceiling of the cathedral’s crypt. Using a detailed survey plan to determine where the loft’s legs imposed highest loads, a specification was prepared to infill voids at these locations with brick and to re-bed specific tiles – a distinct intervention that is reversible in future. The loft is designed to hold a 1,200kg organ console, the organist and companions 3.5m above floor level on incredibly slender 50mm square section legs.

Dynamic finite element analyses of vibration and footfall indicated that this elegant structure could be free-standing. However, the platform did sway just enough to disturb some users and distract them from playing. The design had anticipated this possibility and included a subtle reinforcing pin to be fixed, if needed, into one of the bed joints of the existing stone columns at high level.

Every connection in the steel frame and the walnut panels had to be both high-performance and invisible. Millimetre deserves great credit for achieving the absolute precision asked for in the countersunk bolt holes and seamless welds, and for its joinery expertise in developing the design of the timber panel joints.

Will York, project engineer, Price & Myers

 

Fabricator’s view

Millimetre was asked by Caruso St John Architects to help develop the technical design for the Canterbury Cathedral organ loft, advising on manufacturing techniques and viability. We followed this with an extensive prototyping and samples process to finalise the procedures, materials, and finishes.

The mild steel hollow sections were all bespoke and fabricated in our workshops, enabling us to provide a box section with sharp corners (as opposed to an extrusion). These were zinc-sprayed and patinated to a warm dark grey, then protected with several coats of wax finish.

The joinery timber panels were also bespoke and intricate in their construction, with several considerations given to accommodate the movement of the timber laminates over time. The timber selected was American black walnut, and the build-up a solid core faced on both sides with solid walnut construction veneers of different thicknesses, the final thickness of the panels being 50mm. Making these joinery panels called for a meticulous process. Each panel, some up to 4m long and 250kg in weight, had to be made to the precise millimetre and all were fixed invisibly.

Karn Sandilands, director, Millimetre

 

Working detail

The timber platform of the organ loft is held up on a light framework of steel, with a thin section and a vertical proportion that relates to the stone tracery of the adjacent quire screen. The steel is blackened with a zinc coating, patination and wax to match the surfaces of other metalwork in the cathedral, such as the gates and railings around the tombs and chapels.

The platform and stair enclosure are made with American black walnut cross-laminated panels, lightly stained and oiled. The colour matches the dark hardwood joinery present throughout the cathedral, from the 14th-century oak doors, mahogany benches and the 19th-century oak choir stalls. The walnut is sometimes used as a veneer, and sometimes as solid staves in areas of higher  wear. Veneer is used rather than solid planks to achieve a taut surface, where the figure of the wood grain is stretched from one side to the other, recalling a tracery screen.

The dimensions of the steel and timber parts are closely related, allowing for continuity between them and a sense of ‘overallness’. The steel sections are welded from flats, and ground to achieve a square edge, allowing for precise dimensions and flush relationships to the timber. The dark colouring of both connects them further, resulting in an ambiguity. One feels cold, the other warm.

Will Pirkis, project architect, Caruso St John

 

 

Project data

Fabrication September-November 2019
Installation  November 2019
Client The Dean and Chapter of Canterbury Cathedral
Construction cost £150,000
Procurement Invited tender with PQQ
Form of contract JCT Minor Works
Project architect Will Pirkis
Structural engineer Price & Myers, The Morton Partnership (cathedral engineer)
Services engineer Ritchie & Daffin
Main contractor Millimetre