Bourne Hill Offices.

When Salisbury District Council wanted to consolidate their offices into one location, they commissioned Stanton Williams to design an extension to a magnificent Grade II*-listed house dating from the 1670s, on a site of archaeological interest with potential medieval remains, delineated by rows of established trees.

Location

Salisbury, UK

Client

Salisbury District Council

Architect

Stanton Williams

Project Value

£13.6 million

Status

completed 2010

Expertise

Structures

The new building updates a dilapidated Victorian wing and extends, on a relatively narrow floor plate, away from the house. We worked extensively with English Heritage and specialist archaeological consultants, monitoring the existing building and surrounding land to ensure a delicate approach which would not cause damage to areas of decay due to poor maintenance. Appropriate traditional methods were specified where repairs were necessary, such as hair lime plaster, local stone and timber laths.

In terms of structure, the new building is a flat concrete slab on a column grid of 9 × 10 m. Environmental issues were key to the design, in helping the Council to promote their commitment to carbon saving. Cost efficiency was paramount and led us to consider a number of options to be able to deliver a high-quality structure within budgetary limitations.

We needed to engineer a frame which would bear the weight of the sedum roof installed in a bid to obtain a BREEAM ‘Excellent’ rating. The use of concrete maximised the thermal mass, and we proposed a mix incorporating 55 % GGBS cement replacement. This is estimated to have reduced the carbon content of the building by up to 20 %.

The end result is a design which, despite its minimalism, suits its historic surroundings. The reflective glass façade softens the building’s lines and lessens its impact on the adjacent greenery. Stone-clad fins outline an external walkway, delicately engineered to function within tight dimensional parameters. A new glass-floored bridge was introduced between buildings, innovatively supported on two hollow steel sections and hanging cables from the roof.