Project Reflections : 1 Grosvenor Crescent

This once magnificent Victorian townhouse had been for many years the headquarters of the Land Tribunal (Land Court). As a government building the external fabric, the ashlar walls and slate roof were in excellent condition and had been well looked after over the years. Internally, the rooms had been altered to accommodate as best as possible, changes in the way people work but, in most areas, existing doors, architraves, skirtings, cornices etc. remained in good condition.

Carlton Properties purchased the property around 2007 with a desire to convert the building into 6 luxury apartments. The building already had consent for a less than sympathetic conversion that significantly altered the existing spaces with both removals and additions. We were brought into the project part way through the planning application stage when the client started to have misgivings over the expertise of the incumbent architect for delivering such a sensitive project.

Our overall design strategy was to work with the existing layout of the building, limiting the intervention to the existing fabric whilst still meeting the required accommodation schedule. A key decision we took early on in order to follow this strategy was to install sprinklers to the entire building. This allows significant relaxations to be negotiated with Building Standards in terms of fire regulations thus negating the need for new unsightly protected lobbies and fire doors and working much more with the existing layout.

Living spaces for each apartment were located in the large principal rooms and designed as open plan kitchen / dining / sitting spaces thus avoiding any physical changes to these space except for decoration. Kitchens were carefully designed, and an extremely contemporary minimalist style adopted in contrast with the existing highly decorative rooms. In the former land court on the first floor, the largest and most significant room in the building, the kitchen was completely free standing as an island unit in the centre, dividing the sitting from the dining area. Apart from the kitchen installation, the room was completely unaltered.

Bedrooms were allocated to the smaller, less significant spaces and where subdivision was required, existing ceilings and cornices were left intact and unaltered by installing new lowered plasterboard ceilings.

The least significant rooms or windowless stores towards the rear of the property were reserved for bathrooms where intervention from new services is always intensive.

As the conversion worked very much with the grain of the building with limited sub-division. Much of the physical work resulted from the installation of services and the upgrading of certain aspects of the building to meet the building regulations requirements.

Many of the window cills were extremely low, some only 200mm above floor level and therefore posed a safety hazard. This was resolved with very little impact on the existing fabric. Radiators were installed in front of each window reveal preventing people from getting too close and frameless glass was installed internally as a barrier secured with discrete chrome clamps.

Trickle ventilation had to be provided to all the rooms. Where possible, this was done by making the top sash openable. Where this was not possible, trickle vents were installed but these were located in the meeting rail minimising the visual impact.

Secondary glazing was resisted as a means of upgrading the thermal performance of the window with each window simply being carefully overhauled and draught stripped. Many of the existing shutters were repaired and made operational, thus improving the thermal performance of the window when closed after dark.

Although pressed by Building Standards to do so, insulation of external walls was also strongly resisted mainly due to the decorative cornices in place and a compromise was reached by only insulating less significant rooms to the rear or within the basement. This was done using a new independent timber frame, set 25mm away from the existing internal face and insulated with mineral wool between the studs. A discrete ventilation gap was provided at skirting and cornice level to avoid interstitial condensation.

Where existing ash deafening had been removed following previous services installations, this was replaced with a granular fill on the existing deafening boards prior to new services being installed.

Although the number of required fire doors were significantly reduced as a result of installing sprinklers, the entrance doors to each apartment leading from the common stair still had to achieve a 1hr fire rating. These were significant existing doors so removal wasn’t an option. The upgrading was achieved using intumescent paper to the panels and paint to the mouldings. Any excessive gaps around the door leaves were reduced by installing timber lippings, in the same species as the door. Intumescent strips and smoke seals were installed around the door perimeter. Concealed self-door closers were chosen in favour of the visible over head ones.

1 Grosvenor Crescent is a model project that demonstrates the benefit and role a sprinkler system can have at many levels in the conservation of a building that is being adapted for re-use. Firstly, a sprinkler system can safeguard the future of any important building should a fire break out and with minimal intervention architecturally as a result of the installation. It is often our default position to install a sprinkler system for this very reason.

Secondly a sprinkler system can be used to offset the requirement to meet certain fire safety regulations such as fire doors and smoke lobbies. Installing such lobbies on a listed building can completely change and ruin its character and history.

David Johnson

Architect, Director