Darwiri College Study Centre Cambridge

Jeremy Dixon & Edward Jones

Subject | Darwin College is a small postgraduate college of Cambridge University. It comprises a number of old buildings on the River Cam, one of which was once the home of the Darwin family. Hence the name of the college. In 1989 an architectural competition was held for a structure to connect the buildings and provide reading and study facilities for the students. The site itself was exceptionally difficult. Hemmed in by the existing buildings, it was 45 metres in length but only 6 to 8 metres wide between the Cam and the very noisy Silver Street. The south side, facing the mill pond, is very attractive, but the noise and pollution from the street had to be reliably excluded, which was no easy task.

The architects Jeremy Dixon and Edward Jones won the competition with an idea that was as simple as it was effective. On the street side a low continuous wall and on the river side closed-in computing rooms at ground level with the study area above them, open to the river. The load-bearing system was to be of wood. From the tenders received it was seen that, on account of the economic crisis, home-grown oak was the cheapest solution. In the required dimensions, however, it was available only freshly felled and not seasoned. That meant long drying-out times, during which the timber would shrink and move. The problem, therefore, was to find not only a suitable connecting structure but also to create connections between the timbers that could be adjusted and tightened as the drying of the timber took place. The difficult structural analysis was assigned to the building engineers Ove Arup & Partners.

Design | On the street side the building is bounded, optically and acoustically, by a continuous storey-high wall that follows the slight curve of the street. Along the inside of the wall runs the corridor that gives access to the whole building and at the west end leads to a small recreation room communicating with the individual work areas. There are also bookcases there running the whole length of the corridor. On the river side of the corridor a row of four computing rooms is located. Between these, stairs lead to the reading and study rooms above, which are also open to the access corridor with its bookcases. The computing rooms have small windows in the masonry wall, the upper reading-rooms wide strip

Location

Darwin College, Cambridge CB3 9EU, Great Britain

Client

Darwin College Cambridge Architect

Jeremy Dixon & Edward Jones, Architects, London Project Architect Alison Greig

Structural Engineer Ove Arup & Partners, London

Project Engineers Roger Hyde, Sarah Mal-drum, Peter Ross, Mick White

Timber Construction Henry Venables Ltd., Stafford

General Contractor Rattee & Kett Ltd., Cambridge

Date of Completion 1994

Costs

The cost of the building came to between 1 and 1.5 million English Pounds and was within the limits of the estimate.

6 I South facade seen from river.

7 | View of access corridor. On left: roadside wall and row of high-level windows. On right: computing rooms under reading and study area.

8 | Section of south facade, scale 1:30. Floor construction: load-bearing principal cantilever beams 365 x 150 mm, intermediate cantilever beams 290 x 75 mm -on top 20 mm tongue-and-groove oak parquet, underneath 2 layers of 12-mm chipboard and 20 mm ton-gue-and-groove oak facing; between beams 100-mm heat insulation layer. Facade construction: parapet from exterior to interior: 25 mm oak facing on 175 or 75 x 25 mm oak frame on lathing, protective sheeting, 75-mm-thick heat insulation, vapour barrier, 18 mm plywood boarding, window of oak with heat-insulated double glazing. Flat roof from top to bottom: lead covering, 20 mm boarding, 120 x 50 mm squared timbers, between these 70-mm-thick heat insulation and 50 mm air space, vapour barrier, 20 mm plywood boarding, 150 x 100 mm roof beams, 12 mm gypsum plaster board.

windows opening towards the river and the south. The upper storey also cantilevers out some 1.5 m over the water, forming, as a structure wholly of wood, an impressive contrast to the masonry base.

Above the wall on the street side is a row of soundproof dead lights and over these a pitched roof that rises to a row of windows above the reading area in the upper storey. The pitched roof thus not only amply covers both levels of the corridor and reading area, it also opens up the building to the south, neatly closing it off on the street side. The whole of the interior is predominantly of wood, such surfaces as tables, balustrades, windows and doors being finely smoothed and finished. The structural timbers have been left deliberately rough and fissured, thus offering an interesting contrast to the surfacing wood, likewise all of oak.

In the working area all the windows can be opened by hand. The row of high-level windows, however, forms part of a sophisticated ventilation system combining natural with automatic heating and cooling: at the east end of the access corridor there is a staircase leading to the upper level, as well as a ventilation stack with openings that can be closed by wooden flaps. These and the high-level windows open automatically with a rise in air temperature, thus ensuring air movement without the need for a fan. The automatic control system also closes the flaps against wind and rain. This system provides natural cross-ventilation while keeping out street noise.

Structure | Only the upper floor is actually a timber construction, the ground floor consisting mainly of the outside walls on the street and river sides. The river wall is reinforced every 5.5 m or so by cross strips of twin masonry walling about i m in length and 1.10 m apart. This spacing also forms the basis for the spacing system chosen for the whole of the interior. The double walls are joined under the floor by reinforced concrete slabs 300 mm thick. Placed behind the riverside wall, these concrete slabs not only carry the staircases leading to the upper floor, but also form the foundation for the timber superstructure.

The primary posts are of oak 250 x 250 mm and are fixed to the inner corners of the concrete slabs by steel T-sections and anchored to the back ends of the riverside main cantilever beams. The row of primary posts forms an axis between the body of the building cantilevered over the river on the one side and the pitched roof that sweeps down to the street on the other. Throughout the length of the building stand double primary posts at intervals of 1.10 m and joined together under the high-level windows by two 250 x 100 mm beams, one above the other to ensure greater stability. These thus form the fixed points for the whole construction. The cross beams cantilever out on both sides carrying intermediate Gerber-like coupling beams of the same dimensions. The lower cantilever, which is longer than the upper, looks as if it were supporting these. At the very top, above the row of high-level lights, the primary posts carry the ridge purlin for the pitched roof.

The part of the building that cantilevers over the water is carried mainly by 365 x 150 mm cantilever beams, which are fixed to the primary posts and rest on concrete slabs placed on the outer wall. At the cantilever end roughly 1.5 m from the outer wall there is a 325 x 100 mm head, which in the wide spans between the primary posts is supported further by visible 150 x 150 mm struts stretching from the brickwork wall. On the head, the same distance apart as the primary posts stand the 150 x ioo mm posts that carry the facade. These are connected at the top by the 150 x 150 mm boundary beam and at parapet height by a ioo x 100 mm rail. Between the boundary beam and the above-mentioned continuous twin beams lie the horizontal rafters of the riverside part of the building. 100 mm in width, they display a height of 150 to 250 mm for roof pitch.

9 | Interior showing primary posts and double beams with screwed anchor bolts and points of support for suspended beams. The windows are also provided with adjustable anchor bolts.

0 0

Post a comment