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Attingham Hall, Shrewsbury

From Workstream Pulse, Autumn 2014

Built for the first Lord Berwick in 1785, Attingham Hall near Shrewsbury was owned by the same family until it was acquired by the National Trust in 1947 over 160 years later. The hall's stunning picture gallery roof, designed by renowned Regency architect John Nash, used what was then the cutting-edge structural technology of a cast iron framework of curved ribs to hold a number of convex glazing panels that refracted light over a wide area to reach the lower levels of the gallery and illuminate Lord Berwick's collection of paintings.

Completed in 1807, Nash's roof, while spectacular, was never completely watertight and water ingress was a continuous problem until a glazed cover was installed by the National Trust forty years ago. Unfortunately, the 1974 cover was only ever partly successful and came to the end of its life. The Trust therefore commissioned a modern solution for the cover's replacement and construction work on the project began last year.

The new protective cover for the picture gallery roof at Attingham Hall involved the construction of a state-of-the-art glazing system mounted on steel trusses over the entire expanse of some 158 square metres. This effectively created a "giant display case" for Nash's original structure.

Weighing in at some 20 tonnes, the new secondary roof of Pilkington's Planar structural glazing required extensive demolition and building work to install. This created particular challenges for main contractor Norman & Underwood given the need to maintain the original architecture of this important heritage site and the National Trust's insistence that the hall should remain open to visitors during the whole year that work was carried out.

Norman & Underwood called on Workstream's Engineering Services division to survey the works for the installation of the new glazing. The company's engineers successfully completed their part in the project over the months of April and May this year.