Ramboll has completed the redevelopment of the Lighthouse building in Kings Cross.
The final elements of construction work marked the end of a renovation project on the historic seminal building in London, which now boasts an additional storey and a mezzanine level.
Situated adjacent to Kings Cross Station the iconic Grade II listed building, which dates back to 1875, had been on Historic England’s Buildings at Risk Register and its historical features have been carefully and meticulously conserved.
The restored building now comprises five upper storeys and a mezzanine roof space. The new curved roof structure created an additional storey-and-a-half and was designed to mimic the vaulted roofs of the nearby train stations. The ground-floor will be a dedicated retail space with the upper floors housing offices.
Engineering and design consultancy Ramboll was commissioned 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 came with a number of complex challenges, not least that its footprint is directly situated over two underground tunnels – TfL District Circle and Metropolitan and Network Rail Thames Link.
The proximity of the tunnels meant that it was vital that the load of the building remained within strict parameters to prevent movement. In order to overcome this challenge, the demolition and construction sequence was carefully designed and a lightweight structure replaced the heavy masonry to allow an additional floor to be built on top of the building.
Advanced engineering analysis was conducted to predict and measure movement during the construction phase.
The proximity to the railway tunnels also caused a number of issues regarding vibration and noise in the building and extensive anti-vibration measures were put in place to counter this. Elastomeric bearing pads were used to isolate the frame, windows, floors and finishes from the vibrations.
On Historic England’s Buildings at Risk Register the interior was largely derelict and unsafe for use before restoration began.
The iconic lighthouse tower was completely renovated following a survey of the structure which identified decaying timber. It was clad with pre-weathered zinc and capped in lead while the original weather vane was reconstructed. The existing timber structure at the nose of the building has been treated as a period restoration with lime plaster on laths.
By unlocking the value of this complex site, the redevelopment was successful in securing this historic building’s long term viability.
“By using some of the very latest advanced engineering analysis at an early stage of the project, 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,” said Jackie Heath, an associate at Ramboll.
“This provided reassurance to the client and rail authorities of the feasibility to proceed with the new storeys and roof, unlocking the value of this technically difficult site and securing this historic building’s long term viability.”