Case Study / Waterproofing

Grade 2 listed Bank Conversion, London

Transformation into a Modern Restaurant and Music Venue

We are excited to share our involvement in the ambitious redevelopment of a Grade 2 listed old bank building into a dynamic restaurant and music venue located in the heart of London. This £14 million refurbishment project is situated within the prestigious Harley Street Conservation Area, near the historic Cavendish Square.

Cavendish Square, established in the 18th century, has long been a notable landmark in London, surrounded by elegant Georgian architecture and serving as a hub for both residential and commercial activities.

The building itself has a rich history, having served as a bank for many decades. Its architectural significance and heritage value have made it a prominent feature in the area. The transformation aims to breathe new life into the historic structure, blending modern amenities with its rich architectural heritage.

The intention is that the former banking hall will provide the main dining space, with smaller dining areas on a newly constructed mezzanine floor and the first floor at the eastern end of the building. The basement will house the kitchen and back-of-house facilities, along with a bar, lounge, and dancefloor. Additionally, a ground floor bar is proposed adjacent to the main entrance at the western end, with two small cellar bar areas also planned for the basement.

Method

To achieve these goals, the client has opened up the basement areas and lowered the floors in the vaulted sections and corridors, creating service voids for plant and equipment.

MacLennan has been specified by a returning client to install a comprehensive cavity drain system throughout the entire basement and its six vaults.

The vaults, located in the west of the building present unique waterproofing challenges due to the way water runs over the membrane instead of in the void behind it. It is now a requirement of British Standards that all vault membrane systems are tested with water during and after installation, as well as before and after the installation of finishes.

Cavity drain membrane will be fixed to the internal walls with surface plugs in vertical installations, thus creating a water management system to control water after it has penetrated the structure.

The system directs penetrating water into a drainage system and a collection sump before using a pump to discharge water from the building.

Two options for channel installation were considered: in the slab or on the slab in grooved XPS insulation. MacLennan opted for the on-slab method, as it is a simpler and less expensive construction for the building contractors. This approach also provides the benefits of insulation, although it raises the floor level slightly. The floor insulation aligns with the top of the channel, creating a recessed space and protecting it from movement.

Results

MacLennan successfully installed a fully compliant waterproofing system to the basement of the Grade 2 listed building in Westminster's exclusive financial area.

The work was carried out within the agreed time frames and budget, ensuring the project's smooth progression.

We provided our own design and were engaged to carry out the installation, offering a comprehensive design, supply, and install service. As part of this service, we assume full liability for the waterproofing design, which is covered by our Design Guarantee and protected by our £10 million PI insurance.