York Railway Station
Patent Glazing for the Glass Roof - first major refurbishment for over 30 years

Project:
Railtrack plc; Regeneration Programme for York Station. Roofing Refurbishment.

Supplier:
Lonsdale Metal Company Limited

Product:
Patent Glazing products used for the Glass Roof
SkyGard
SKY 71 glazing bars

Glazing Contractors:
Weatherwise UK Ltd.

Architect:
White Young Green

Main Contractor:
C. Spencer Ltd.

Re-opened in 1877, after a four - year closure for extensive rebuilding, the new, enlarged, York Station was immediately hailed as one of the great buildings of Victorian England. It was the largest railway station in the world, with four massive arches and thirteen platforms. Today, York still impresses and not just architecturally either. Serving the busy East Coast mainline route, primarily between Glasgow, Edinburgh and London(but also cross-route between Newcastle, Manchester and Liverpool), the station has to cope with around 800 trains and thousands of passengers each week. Inevitably in this environment dirt, vibration and the elements take their toll on the structure, not least on the patent glazing systems present on the roof. Apart from routine maintenance, no major refurbishment work has been carried out on the 11,000m2 of roof glazing for over 30 years and the latest inspection showed that remedial work was necessary.

Lonsdale Metal Company Ltd. with their reputation as one of the UK's leading manufacturers of patent glazing, rooflights and atria systems, were appointed to handle the contract. Lonsdale, who began trading back in 1946, have always believed that their role should be to concentrate on the development, manufacture and supply of leading-edge products. And, fully backed by the provision of a comprehensive technical support package, leave the installation to specialist glazing contractors.

Time takes its toll on the patent glazing… and the glazing bars

A mixture of glazing types are present throughout the glass roof, ranging from 6mm (1/4"), rough - cast glass, to Georgian wired 7mm mesh reinforced glass (19mm diagonal and 12mm square). Naturally enough, the older the glass, the more encrusted the dirt and algae growth, plus the fact that whilst the rainwater mostly runs along the glazing bar lower surfaces, it was also finding its way down the internal face of the glass. A number of the glazing panels were cracked, probably due more to strains within the system than to external damage. Stress raisers are usually due to trapped dirt, over tightening of the glazing clamps, or poor cutting of the glass, promoting progressive cracking of the panel.

It doesn't stop there…
There were many instances of bottom panels of glass actually having slid down the roof, lodging on the footways.

As for the glazing bars, there were four types in use throughout the glass roof. A uPVC system, a steel

"Perfection" Bell type system and two Aluminium Wing Bar types (short and medium span). The uPVC type was found to have little wrong with it. However, whilst the other systems had performed relatively well, in many areas sealing cord problems had caused glass panels to come loose. With all these systems, the gap between the glazing bar and clamps is a constant dimension and any significant change in the cord diameter, after installation, will inevitably cause the glass to become loose. Elsewhere, corrosion was beginning to appear where the galvanising had broken down and a further practical factor was that production of the "Perfection" system had ceased many years previously and replacement parts were simply no longer available.

4500m2 of glazing to be replaced - with the station fully operational

After an extensive inspection of the entire glazed roof area, it was decided that getting on for half of the 11,000m2 of patent glazing should be replaced. However, a station closure, even a partial closure, wasn't an option and because of the high volume of passenger traffic on the concourse and platforms, neither was the use of scaffolding. Lonsdale and Weatherwise UK, the glazing contractors, considered the situation and decided that three levels of safety netting suspended under the working areas would provide ample protection for station users, whilst the installers could use crawling boards, with each operative wearing a full arrest system.

But what about roof access for the operatives and the movement of materials?

Iain Grimley, Contracts Manager for Weatherwise, remembers it well: " A mechanical hoist was a must. We had to strip out all of the old material and take delivery of 1200 new SkyGard glazing bars, along with 4500m2 of Georgian wired rough - cast 7mm glazing glass panels. However, there was only one access point to each of the arches and they were at one end only. Consequently, as we worked our way along each roof - and only one panel could be carried at time - the distance got further and further. In fact, the platforms are around 230 metres in length, so it was possible to have a round trip of 460 metres to get one glazing panel in position at the furthest point from the hoist. Our team has never been so fit!"

Lonsdale lead Flashings…
The glazing bars were attached to the existing steel structure using M8 single hole fixing shoes. These were positively fixed at the top, sliding at the bottom end. An isolator was used to avoid the possible problem of bi-metallic corrosion between dissimilar metals. Remedial work was also necessary at the ridge and junctions, to replace lead flashings and Lonsdale supplied the glazing bars ready notched to accommodate the replacement lead flashing.

A closer look at SkyGard

SkyGard glazing bars, with their traditional "T" bar appearance, are very similar in appearance to the style used previously on the roof at York Station. This, combined with their performance characteristics, overall cost-effectiveness and the company's reputation for reliability and technical support, were the key factors in Lonsdale being awarded this particular project. A Mill Finish, as used at York, is standard but a range of architectural finishes is available. This includes polyester powder coating to BS6496 in standard RAL, Syntha Pulvin, or BS colour ranges.

There are four variants in the Lonsdale SkyGard range (SKY 50 / 65 / 71 / 76), each offering different span options between top and bottom fixings. With the exception of type SKY 50, the others in the range are available for single or double glazing applications. Type SKY71 was used on the York Project and is currently being installed to refurbish the 23,500 m2 roof at Waterloo station. SkyGard patent glazing bar components (bars, cappings, beads and fixtures) are extruded aluminium alloy 6063-T6 to BS EN 573-3:1995; BS EN 755-2:1997; and BS EN 755-9:2001(which have superseded BS 1474). Fasteners provided are either stainless steel to BS EN ISO 3506 Grade A2, or mild steel bright zinc plated.

Richard Burgess, Sales and Marketing Director for Lonsdale, observes. "As a company, we are successful for a number of reasons, but four stand out. Our range allows us to offer the most cost-effective solution for any given application, our product quality and technical support is probably the best in the market and we have enormous belief in our own capabilities, which from a sales point of view makes us pretty tenacious. The fourth though, is being able to build trust with the contractor and work successfully as a team on the large, logistically complicated projects. Certainly Weatherwise did a great job at York and between us, we managed to complete a project in just under four months, that was originally scheduled to take seven".

For all technical enquiries please contact:
Ray Fraser
T: 0208 801 4221
E: ray.fraser@lonsdalemetal.co.uk
WEB Site www.lonsdalemetal.co.uk