Ramboll has finished redeveloping the Lighthouse building in Kings Cross.
The completion of the final elements of construction work marked the end of a renovation project on London’s historic seminal building, which now has an additional storey and a mezzanine level.
The iconic Grade II listed building, which dates back to 1875 and is located adjacent to Kings Cross Station, has been on Historic England’s Buildings at Risk Register, and its historical features have been carefully and meticulously conserved.
The restored structure now has five upper storeys and a mezzanine roof space. The new curved roof structure added a storey and a half and was designed to resemble the vaulted roofs of nearby train stations. The ground floor will be dedicated to retail, with offices on the upper floors.
Ramboll, a design and engineering firm, was hired by developer UK Real Estate to provide structural engineering, advanced engineering analysis, 3D laser scanning, MEP, and conservation services.
The redevelopment of the Lighthouse building presented a number of complex challenges, not the least of which is that its footprint is directly located over two underground tunnels – TfL District Circle and Metropolitan, as well as Network Rail Thames Link.
Because of the tunnels’ proximity, it was critical that the building’s load stayed within strict parameters to prevent movement. To overcome this challenge, the demolition and construction sequence was meticulously planned, and a lightweight structure replaced the heavy masonry to allow for the addition of an additional floor on top of the building.
During the construction phase, advanced engineering analysis was used to predict and measure movement.
The building’s proximity to the railway tunnels also caused a number of vibration and noise issues, which were addressed with extensive anti-vibration measures. To isolate the frame, windows, floors, and finishes from vibrations, elastomeric bearing pads were used.
Before restoration, the interior was largely derelict and unsafe for use, according to Historic England’s Buildings at Risk Register.
Following a survey of the structure that revealed decaying timber, the iconic lighthouse tower was completely renovated. While the original weather vane was rebuilt, it was clad in pre-weathered zinc and capped in lead. The existing timber structure at the building’s nose has been restored as a period piece with lime plaster on laths.
The redevelopment was successful in securing the long-term viability of this historic building by unlocking the value of this complex site.
“We were able to assess the effects of the proposals on the ground and tunnels and minimise load changes on the cut-and-cover masonry tunnels below by using some of the very latest advanced engineering analysis at an early stage of the project,” said Jackie Heath, an associate at Ramboll.
“This reassured the client and rail authorities about the feasibility of proceeding with the new storeys and roof, unlocking the value of this technically difficult site and ensuring the long-term viability of this historic building.”