A heritage assessment helped win support for a new extension on a building in a highly sensitive location in central London.

The scheme will bring about the modernisation of the former BBC offices of Brock House, which opened in 1908  as the Philharmonic Hall. The building is characterised by the red brick walls and Portland stone with quoins and arched window heads.

Heritage consultancy services were provided to assist proposals to make an additional roof extension to this building that sits in the Harley Street Conservation Area. The building is adjacent the BBC, All Souls Church and the Langham Hotel. Initial townscape assessment and heritage advice at the pre-application stage helped formulate a sympathetic rooftop extension that formed part of a detailed planning application.

As a building identified in the Conservation Area Appraisal where a roof extension would be acceptable, we worked to show how the new would be suited. As it would sit within the many examples of townhouses whose butterfly roofs (set behind a parapet)  have been altered and now have mansard roof extensions.

There are variations on the Classical, Gothic and Flemish idiom in the wider context, with red brick, stucco and terracotta being popular mediums. This is most represented by the Victorian mansion blocks above shops on Great Portland Street which have bright red brick and a range of Arts and Crafts detailing.

The Heritage statement influenced the proposed design and its reference to the general scale and height of the existing building. The additional storey expresses itself to the front of the building line on all sides and will be seen as stepping back on a gradual slope. The mansard is an addition that is clearly modern but helping to establish and evoke respect for the Classical style seen on the main elevation.

The changes proposed at the upper level are designed to sit well within the interesting skyline started at the top of Great Portland Street near Great Portland Station and ending at the junction with Oxford Street. A lightweight double storey addition in the context of the Church would reflect well the listed building and its distinct roofline.