Grade II landmark building in London’s Kings Cross
This landmark building is a Grade II listed Victorian property built around 1875, located on an irregular triangular site within a conservation area, and built upon what is now the Thameslink/Network Rail tunnel.

Situated at the junction of Gray’s Inn Road and Pentonville Road, The Lighthouse Building is built upon wrought iron foundation beams, which span the tunnels with traditional masonry and timber construction above.

Comprising a shallow basement, founded immediately on the crowns of the tunnels with ground, first, second and third floors above, the main feature of the building is the listed Lighthouse structure, with a third floor heritage room below at the apex of the building.
Sitting directly above the underground tube tunnel, all the steelwork had to be isolated from underground vibrations. The retained facades would still vibrate but the new structure had to be isolated completely. The interface between the existing and the new structure was designed in such a way that it was able to stop the transfer of vibrations.

The superstructure of the building consisted of a braced steel frame with composite concrete-steel decking spanning between the main beam framework.

The Lighthouse tower at the apex of the building has been retained, together with the timber third floor directly below and all the facades. The roof structure comprised curved beams with the addition of Vierendeel trusses to create a stepped, vaulted look. Due to the elliptical nature of the roof curves, a number of the steels had to be curved to different radii in order to create the desired aesthetic look.

via Flickr http://flic.kr/p/DDTHXu