Image supplied by National Trust/ Richard Knisely-Marpole.
Work has been completed on the new roof, which will ensure the 200-year-old glass and cast-iron structure installed by Nash is protected from the elements – something that had always been a challenge as the original roof, installed in 1807, had leaked from the start.
Architects S T Walker & Duckham, appointed by the National Trust to design the new roof, selected the Pilkington Planar™ system because of its low-profile appearance, high structural strength and high clarity.
The installation, which consists of 133 sq m of double-glazed frameless units supported by steel bowstring trusses, was carried out by specialist conservation contractor Norman & Underwood.
The glazing also filters out UV light, which can be harmful to paintings and fabrics, and the roof design features blinds that will close automatically in order to achieve conservation black-out when the gallery is closed to visitors.
Andy Chamberlain, Restoration/conservation manager at Norman and Underwood said: “This was a complex installation from an engineering standpoint. There are 44 individual double-glazed units, weighing 12 tonnes in total, and ranging in size from 0.75m to 2m and none of them are square.
“A great deal of precision was required in positioning the mounting points, so the manufacturing quality of the Pilkington Planar™ system was critical in getting the installation right as there was no margin for error.
“The new roof also needed to be strong enough to withstand the relevant design loads and meet building regulations, but also light enough for the structural constraints we were working with, and the laminated Planar™ |SentryGlas® System delivered on both criteria.”
Chris Barr, design engineer at Pilkington Architectural, said: “The panes were fixed in place using our Nexus stainless-steel castings, and the Planar™ 902 bolts.
“These fixings were attached to stainless steel spacers that raised the glass above the trusses far enough to allow openable horizontal windows to be placed around the edge of the space to provide ventilation when required.
“To further lower the visual impact of the roof, we have also used newly-developed grey-coloured compounds for the rubber bosses that sit between the fixings and the glass itself and unit edge sealant, where these were previously all black.
“This is a cutting-edge glazing system, just as the John Nash roof it will be protecting was in its day, and it’s great to know that it will be preserving such a significant piece of architectural history.”
Attingham Park was built for the first Lord Berwick in 1785. Today, the stately home and the 4,000-acre grounds in which it sits are the headquarters for the National Trust in the West Midlands.
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