CLIFFORD’S TOWER YORK
Clifford’s Tower, York
For Historic Property Restoration Ltd
Structural & Civil Consultants Ltd advised on temporary works
needed to replace stone stair treads in a spiral stair. The staircase
is an integral part of the wall structure and of the rampart walkway
above. For the removal of any one step it was necessary to assess the
load taken by the element of the newel post associated with that step,
and to design temporary beams and props that would avoid loading the
fragile steps below.
Structural Defects At Clifford’s Tower The Norman tower was constructed in 13th century by Henry ll on an 11th century mound. In 1315 a flood washed part of the mound away and undermined some of the foundations. In recent times the walls appear to have been stabilised but still lean outwards significantly in places. At less robust areas such as where the spiral stairs are built within the walls, movement has left some of the stones in a broken condition. The inclination of the spiral stair in the south-east corner where steps were replaced was approximately 1:10 or 6° from the vertical.