Witherford Watson Mann stitches in a narrow, triple-height extension at Clare College, Cambridge, to create coherent circulation and better accessibility with natural, finely crafted materials
It seems every new building must now have a signature staircase to show off the architecture and offer a unique experience of movement. Witherford Watson Mann’s extension to Clare College, Cambridge, is no exception – a slender column of steps which drops through four floors of immaculate oak joinery, offering vistas across college gardens and the River Cam through full-height windows, and with an unfinished oak handrail inviting a tactile connection throughout its descent. Hopefully, however, it will never be used.
The intricately detailed staircase offers emergency means of escape from top-floor student rooms, but, unlike some of the functional elements in new projects, it is no architectural afterthought.
Externally, the stairwell pokes up as the highest element of a vast timber frame extension, but inside it reveals itself only with occasional glimpses through internal glazing and a sculptural soffit under which students pass en route to a new servery and relaxing River Room abutting the Cam. At 8m across, this generously naturally-lit space is the widest end of a narrow wedged-shaped site WWM had to play with. The other end, touching Trinity Lane, is just 1m wide, but the architect has packed a lot into its 120m length.
WWM’s main task was to improve connections between the living, social, and dining areas of Clare College’s historic spaces, and in doing so improve access for all. Functionally, the extension is a corridor across three levels, but in its experience and material it is much more. Having removed a lean-to roof and peeled back decades of unsightly architectural accretion, the architect cut new openings into the once-external wall, seamlessly stitching the new into historic fabric.
Bricks have been patch-repaired or replaced to match with enough similarity for continuity, but also enough difference to illustrate the building’s evolution. Precast concrete infill elements replicate and continue decayed and lost external stonework to the chimney stack and sills. Purbeck stone is used across the lower-ground floor, the slabs intricately shaped and arranged to avoid awkward joints and junctions.
Such minute detailing is easy to miss in such a transient space, but it is precisely this architectural attention that will future-proof the building over coming decades of daily grind. ‘The timber posts have Purbeck feet,’ says Stephen Witherford, to protect the oak from daily floor mopping, ‘and all the deliveries come down the passage … so trolley guards are built in to protect the corners.'
The Purbeck slabs are cut along the bed, while it cuts vertically through the bed for skirting and vertical faces, a tiny nuance of specification but one which visually offers a solid grounding in situ through what Witherford describes as a ‘geological layering of the stone’. Access covers to now-buried services have a different cut and grain to floor slabs, acknowledging function rather than hiding it, and removing potential visual annoyance when they are inevitably put back into place at a different rotation.
Where Purbeck slabs meet the historic wall, a shallow trough acts as a shadow-gap to visually absorb noticeable differences between perfectly straight new elements and the inconsistent edge of the historic elements.
In a project using a simple, robust palette of materials, oak dominates throughout – across the ceiling, wall panels and escape stair soffit, and also throughout the enormous, gridded frame that is not only structure but interior and exterior architecture itself.
Engineered by Smith and Wallwork with 300 individual mortise and tenon joint details, it was prefabricated off-site before being meticulously connected in situ – Witherford describes it as ‘dancing around all the oddities of the existing building’.
It is a narrow material selection, one which contemporises the patinated oak, brick and stone of the historic building, freeing it to sing in natural light and allowing it to age into a richer version of itself. As Witherford recalls a Clare College Fellow saying on a recent visit: ‘All these materials, this whole building, were here already – but we didn’t really see it before.’