Claridge’s is a five-star hotel in the heart of London’s exclusive Mayfair district. The owners wanted to enhance the services and capacity offered to their guests, but needed more space in order to do it. The hotel’s location meant that extending at street level was not feasible, so an alternative solution was found: excavating under the hotel’s Art Deco wing.
Keeping Claridge’s open during basement construction
When the Maybourne Hotel Group proposed that their Claridge’s hotel extend in the basement underneath its Grade–II listed building, it was advised the hotel would have to close during the works. When it revisited the idea ten years later, Arup and McGee developed a methodology to excavate and construct a five-storey basement while Claridge’s remained fully operational.
This was a truly unique project as it required designing and building a deep basement beneath an 80-year old concrete raft. To add to the complexity, all materials going in and out of the site had to pass through a window opening, as any other method would involve transporting them through the hotel.
5,500m² basement to be created
62existing building columns
100,000m³of material excavated
Proving it could be done
Our structural and geotechnical engineers, together with our advanced technology and research group, McGee and temporary works designers RKD, spent six months carrying out site trials, material tests and analysis to demonstrate that the concept was buildable.
Pioneering solutions with tunnel design
The solution involved hand digging small tunnels under the existing ground-bearing raft slab. Circular shafts 1.8m in diameter were hand-dug up to 30m deep under each of the 62 existing building columns. Working in exceptionally tight spaces, the five-storey high reinforced concrete columns were built within the shafts, up to the underside of the existing raft, providing vertical support to the building above. To protect the hotel, real-time monitoring and the facility to jack ground settlements or heave was established at each column location.
Following the mining phase of construction the basement work was complete. The process was then complemented by hand-excavated deep tunnels and shafts which made way for the distribution of building services.
The additional 5,500m² of space houses a range of facilities including a spa, swimming pool, wine cellar, additional plant and back of house facilities. All of these were developed in the Claridge's basement with no disturbance to guests, through our pioneering construction designs.