Some 14 years after the initial feasibility study, Derwent London is going ahead with a £30 million office and retail development on 40 Chancery Lane, designed by Bennetts Associates.
On the drawing board: 40 Chancery Lane
Construction work starts in the new year on the courtyard-style development, located on the corner of Chancery Lane and the pedestrianised Cursitor Street. This site was largely occupied by buildings from the 1950s and 1960s, which are currently being demolished. To the rear of the site along Took’s Court, the development will incorporate two small 19th-century buildings, which are being remodelled internally but with the facades retained. In total, the net internal area of the development is 9,400sq m with a courtyard of 475sq m.
Captivated by the rich fabric of the Chancery Lane area with its collegiate-type streets, alleys and quads, Bennetts rejected a conventional deep-plan-with-atrium building type. Instead, the architects grouped accommodation around three sides of a publicly accessible courtyard in order to resonate with traditional building patterns.
This approach creates one 18m-deep floorplate that wraps along Chancery Lane and around the corner of Cursitor Street and another on Cursitor Street, separated by the main stair/lift core.
A slimmer, 9m-deep floorplate is at the back of Took’s Court, separated by a narrow atrium to accentuate the contrast between the new and retained buildings. Access to the courtyard is via a passage leading off Chancery Lane, adjacent to the building’s reception.
The scale of the travertine-clad development responds to the different conditions around the site. The Chancery Lane and corner element is based on a 6m-wide grid to reflect the greater scale of the Chancery Lane streetscape, while the Cursitor Street-fronted accommodation has a 3m grid in response to the narrower street, but with the same proportion of glass to stone.
On Chancery Lane, the new building rises to four levels with a two-storey rooftop pavilion in a single step back, while, on Cursitor Street, there is a single floor office pavilion with a further set back for the plant area. A common visual language will, says Bennetts Associates’ founding director Rab Bennetts, ensure that the development reads as several companion parts to the same building.
“We took the view that it wasn’t the place for a very glassy building,” says Bennetts. Instead, the design has a pattern of solid and glazed verticals to complement the character of the local area. It has enough solid facade, combined with 475mm-deep window reveals and fritted glass beneath desk height, to give sufficient light while avoiding the use of sun shading. This is possible with the use of high-performance, triple silver-coated glass that gives a clear rather than tinted effect. Each bay includes a 300mm-wide openable vent. The glazed roof pavilions have extra fritting.
The external travertine facade contrasts with the highly glazed courtyard, which has three scenic lifts along the elevation of the service core at the entrance to the courtyard. Neighbouring properties to the north of the courtyard will be flanked with timber screens and climbing foliage.
“It’s very sleek and light without the stone veil that goes around the main street,” says Bennetts.
40 Chancery Lane will be rated Breeam Excellent. Central to the building’s cooling strategy is the use of a passive chilled ceiling system fed by chilled water directly below the structural slab.
This heat transfer system is covered in white, flat and featureless plasterboard soffits for a minimal appearance. By eliminating the need for an unsightly suspended ceiling, this system enables floor to ceiling heights of 2.9m, with lighting suspended off the boards. Fresh air is brought in through the raised floor and drawn up and out through vents to give the option of natural ventilation around the perimeter.
The double-height reception will include a mezzanine, set behind glass, although there is a provision to convert this into a balustrade and install a spiral staircase in the reception if the whole development is let to a single tenant.
The reception will feature a leather wall behind the reception desk along with concrete and dark grey Caithness stone flooring. This will continue into the courtyard as a border, with granite setts in the middle and silver birch planting. Artist Susanna Heron is creating a piece for the double-height passageway leading into the courtyard while, inside, a sculpture by Sophie Smallhorn contrasts with a largely monochromatic interior palette.
“Derwent have been absolutely delightful. They really do have a sensibility for design and really push and challenge. It’s been a very stimulating process,” says Bennetts.
Work is due to be completed in September 2014.
Bennetts specified stone for its grain
The 40 Chancery Lane project is the first time that Bennetts Associates has specified travertine as cladding.
“The area is characterised by stone and brick, and we were more comfortable with stone. That brings you towards Portland stone or an equivalent, but that can be a bit dull. So we looked at travertine with a similar colour to Portland stone but with more grain,” says Rab Bennetts.
Both the practice and client Derwent liked the stone’s pedigree as cladding for such notable buildings as Louis Kahn’s Salk Institute in California.
“We’re doing mock-ups of travertine to see how figured it should be. The one we like has some grey, grainy movement to it.”
The stone will be used unfilled and matt in piers of 2,000mm on the 6m Chancery Lane elevation and 1,000mm on the 3m bay Cursitor Street elevation.
On the face of the piers it will be 50mm thick bonded to a precast concrete backing with 100mm on the side flanking the Cursitor Street floorplate and 200mm on the side flanking the Chancery Lane floorplate to give a greater sense of solidity.
The travertine piers reflect the concrete structure of the building with flat perimeter columns holding up the floor slabs (supplemented by a row of columns 12m into the plan). A precast concrete string course with a weathering drip along each level is designed to maintain consistency of surface weathering by avoiding areas of streaking.
Travertine is limited to the external elevation, with the courtyard fully glazed.
Client Derwent London
Architect Bennetts Associates
Structural engineer AKT II
Services engineer Arup
Quantity surveyor Davis Langdon
Landscape architect J&L Gibbons
Contractor Morgan Sindall