Image relating to FROM FOGS TO FAME, WITH WELSH SLATE

FROM FOGS TO FAME, WITH WELSH SLATE

Two types of Welsh Slate roofing slates have been used on the refurbishment of London’s historic Kings Cross railway station.

Some 30,000 Ffestiniog Blue Grey slates were used by T&P Lead Roofing for the reroof of the roof of the Central range, while Penrhyn Heather Blue slates were used by Mundy Roofing on the eastern and western ranges.

The Welsh slates were a like-for-like replacement for the original Welsh slates which had been on the roof of the massive Victorian building for more than 100 years, during the early part of which it had been exposed to London’s acid-laden “pea-souper” fogs.

Following hard on the heels of the highly acclaimed refurbishment of neighbouring St Pancras Station, the King’s Cross refurbishment played a pivotal part in the regeneration of this historic part of the capital.

When specialist contractor JH & RR Mundy Roofing started work on Phase 1 of the refurbishment for main contractor Costain Laing O’Rourke Joint Venture, it discovered that the slate varied considerably in size and quality.

This is not at all unusual on a roof area of this size and age, as Welsh Slate’s commercial director Michael Hallé explained:

“Repairs are carried out over many years, by different contractors under different circumstances,” he said.

Phase 1 of the King’s Cross refurbishment involved redeveloping the Eastern Range – those buildings running along the eastern side of the main train shed – to provide modern office accommodation.

Approximately 30,000 individual 500mm x 300mm Penrhyn Heather Blue slates from Welsh Slate’s Penrhyn quarry were installed, but 20% of the existing slate was also salvaged for re-use.

“The original roof was close-boarded with the slate nailed directly to the 8 x 1in boards,” explained Mundy Roofing’s managing director Roy Mundy. “This didn’t allow for air to circulate beneath the slates and so moisture built up and rotted the iron nails. However, although the roof started to fail as the nails rusted away, a large proportion of the slates themselves hardly deteriorated at all.

“We managed to salvage about 20% of the original slates, all of them Welsh,” he continued. “Most of these we re-used on the southern hip and the return to the engine room.”

The old slates are a mixture of standard, random and diminished course sizes and yet all the salvaged slates have been re-used.

“The salvaged material was all in very good condition despite its age,” said Michael Hallé.

Mundy Roofing worked closely with English Heritage to ensure that the reroofing of the Eastern Range buildings was in keeping with the structure’s Grade I listing.

“We had to keep as much of the original structure as possible, which meant keeping as many of the original timbers and boards, as well as salvaging the original slate,” said Mr Mundy.

Working under a temporary roof structure, and with the roof temporarily dismantled, new mechanical and electrical plant to serve the new office accommodation was installed in the roof space. The purlins were then replaced, followed by the boards.

“But instead of putting the new slates straight back on the boards, we fixed treated battens and counter battens with a breathable membrane between them,” said Mr Mundy. This ensured a free movement of air to prevent the build-up of moisture beneath the slates.

The Blue Grey Ffestiniog slates supplied for the refurbishment project came from the same quarries that supplied the original roofing.

The re-roofing of the Eastern Range buildings is part of a major redevelopment of the whole station. Phase 2 involved re-roofing the Western Range, which is approximately three times the roof area of the Eastern Range, and phase 3 focuses on the main train shed.

 

Testimonial

Roy Mundy said: “There’s more imported slate on the market these days and some of it’s very good. But Welsh Slate is still a premium product. On a historic building project like this, there is no question of using anything else. It has to be genuine Welsh slate.”

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