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Canterbury tale

16 Mar 15 A Danish-built Omme access platform has proved a godsend for conservators at Canterbury Cathedral. David Taylor reports

The Omme 4200 RBDJ has the reach to inspect the tall West Towers of the cathedral
The Omme 4200 RBDJ has the reach to inspect the tall West Towers of the cathedral

The trouble with historic buildings is that, lovely though they are, they require an enormous amount of maintenance.

Canterbury Cathedral – one of England’s most important historicbuildings – is a wonderful mixture of Norman, medieval, tudor and later architecture. It’s been there an awfully long time, but bits are apt to fall off now and then if left untended. That’s why the cathedral authorities carry out a major structural survey of the building every five years in addition to an ongoing programme of inspection and repair.

On a building of this size and intricacy, detailed inspections are not easy. You need to get up close, which is often a problem above ladder height. It’s not feasible to erect a scaffold just to carry out a couple of days’ inspection. But luckily, modern powered access equipment has the answer. Essex-based hire company Paramount Platforms is a regular visitor to Canterbury and is a regular supplier of access solutions to the cathedral’s clerk of works.

“We’ve been supplying all sorts of equipment to Canterbury Cathedral for years now,” comments Paramount’s managing director Lee Kerr. He says that he and most of his staff previously worked with another hire firm but retained their connection with Canterbury Cathedral when they left to set up Paramount.

The company has supplied high-reach boomlifts to inspect the outside of the cathedral on many occasions. But to inspect the inside of the cathedral has always required a second, smaller machine, since any boom-lift capable of reaching the top of the West Tower from the outside would be far too big and heavy to get inside the nave. However in January, when the cathedral once more called on Paramount’s services, Kerr had something tempting to offer them. Two months previously, he had taken delivery of a new Omme Lift 4200 RBDJ, a compact crawler-mounted telescopic boom with a working height of 42m, from UK distributor Access Platform Sales.

A boom of this length is ample for reaching every nook and cranny of the West Tower (parts of which, says Kerr, hadn’t been properly inspected for over a century). But the machine is also compact and manoeuvrable enough to squeeze through the cathedral’s main doors to access the nave.

And once inside, the 25m-high fanvaulted roof could be inspected close up. “We specialise in tricky access jobs, and the Omme range is ideal for jobs like these,” says Kerr, whose company already operates two of the Danish company’s tracked booms in the 23m and 37m working-height range.

The main advantage of the Omme design is its compactness and manoeuvrability. Despite its enormously long multi-section boom, the 4200 RBDJ stows down to just 2.01m in height and 1.75m width (1.35m with the adjustable tracks retracted) so it can get through a standard double doorway.

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Another advantage is the machine’s hybrid power train. All drives are 12V electric, supplied by a powerpack of eight batteries or, if required, from the mains. But the machine’s own 14kW diesel engine provides continuous battery topup when used outside.

Most 40m self-propelled booms weigh something in the order of 20 tonnes; but the Omme 4200 RBDJ comes in at less than 7 tonnes, which is evenly spread by the non-marking rubber tracks. So not only could the machine pass through the doorway, but also it could work safely inside the cathedral without damaging the ancient floor.

Paramount is currently the only UK hirer to offer the Omme 4200 RBDJ, which was only launched last June. And although Kerr insists that he did not buy it specifically for the Canterbury job, its arrival was most fortuitous.

“We do a yearly inspection for the cathedral and last time we supplied a 24m Falke Schmidt TS24 – another specialised machine. When the cathedral asked us to return in February, I offered them the Omme 4200 at the same price,” says Kerr. The machine was on site for three days, during which conservation specialists were able to carry out detailed inspections both inside and out. From there it went straight off to another job in Greenwich, says Kerr. 

Im ready for my close-up

Conservation staff used the Omme 4200 to gain access to the seldom-seen highlevel interior vaulting of the nave in mid- February. The inspection was carried out in preparation for proposed conservation work to the nave roof and West Towers, together with stonemasonry to the upper nave buttresses and conservation of the nave stained glass windows.

The cathedral’s head of stone conservation, Heather Newton, commented: “This particular MEWP was invaluable in facilitating a survey of the nave vault and the exterior fabric of the western towers. It enabled Jo Deeming, the cathedral’s ‘surveyor to the fabric’, and others to assess the condition of the stonework and more accurately scope the work for the ‘Canterbury Journey’ projects”.

The Canterbury Journey is a long-term restoration and development project designed to increase the “accessibility and sustainability” of the cathedral. It is funded by a major grant from the Heritage Lottery Fund and significant support from private individuals, charitable trusts and foundations.

This article first appeared in the March 2015 issue of The Construction Index magazine. To read the full magazine online, click here.

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