Holy screwjacks! It`s a self-raising floor!

An eight-tonne section of floor at Lichfield Cathedral in the English Midlands has been designed to rise by up to 300mm to create an altar platform which can be lowered for concerts and other special events. Previously, a wooden dais used for services had to be removed for such events - and then replaced afterwards. In 2003, this happened more than 130 times.

The church authorities decided that a mechanically retractable platform was needed and called in architect Martin Sutcliffe to design a suitable structure. He had to start from scratch because the idea had not been tried in any other cathedral. He choose screwjacks as the lifting mechanism, rather than hydraulics, because he felt they were cleaner, easier to maintain and more reliable.

Part of the existing floor had to be excavated to accommodate the lifting mechanism. Archaeologists took the opportunity to investigate what lay underneath and discovered several interesting items. A concrete-based, brick-lined pit now supports the lifting gear and the steel platforms (shown below) that carry the movable stone floor.

The 38m² floor uses a combination of 170mm- and 20mm-thick stones to give a solid feel and to create a similar appearance to the original floor. The floor is raised in two stages using Inkoma screwjacks supplied by Drive Lines Technologies. The mechanism was designed by Hovair Systems, now part of British Turntable, and the project engineer was Frank Haywood & Associates.

The cathedral authorities are delighted with the result. "It`s fantastic," says chief executive, David Warrington. "It blends in so well, a lot of visitors are amazed to discover it`s new."