Rayner's Mill, in Huddersfield, was in a sense incomplete, in that it had originally been designed with two more floors. So when the owner, the Holset Engineering Company, wanted to extend its training centre, building upwards was the obvious solution.
The architect decided on a lightweight structure to clearly distinguish new from old and to ensure that the existing foundations would be able to support the additional load. The new roof is constructed from profiled- metal sheets bolted onto curved beams, and is 'split' along the middle to bring natural light into the centre of the space. The building uses passive ventilation, while the overhangs form a perforated stainless-steel sunshade which provides protection from solar gain and glare. A perforated steel deck running around the perimeter of the building serves as both a maintenance walkway and a place for staff to admire views of the surrounding hills.
Because of the tight budget constraints, the client was keen to make use of the existing stairs and lift, but 'after quite a lot of persuading and cajoling' by the architect, the main circulation has been moved to a new lift and stair lobby, clad in local sandstone to match the existing mill, but with a full-height plane of anti-sun green glazing. This leaves a far more flexible floorplan - a
15 x 46m open-plan space with an escape stair at either end.
The tender cost of £1.69 million (including repairs to the original building) rose to £2.21 million as a result of unforeseen decontamination costs as mercury, cyanide, cadmium and arsenic were found in the walls. 'It started during demolition for the two end staircases,' recalls Zbyszek Plocki, a director at James Cubitt & Partners. 'We knew something was wrong when the protective masks people were wearing started to turn green.'