Glass with stone, glass with metal

The Churchill Place retail area is the fourth below-ground retail area to be built within the Canary Wharf development in London’s Docklands. Although dwarfed by the headquarters of Barclays Bank, Churchill Place is notable for its use of glass laminated with onyx marble.

‘When you look at the entire elevation it’s like looking at a mural’, says architect Shirley Fujikawa of Studio U+A Ltd, speaking about the flat West facing facade, where a 4mm layer of onyx is laminated in the inner glass pane of a series of IG units. ‘That particular facade was considered more important. Just to leave it all glass would be missing an opportunity.’

The stone has a translucent quality about it, with veining, rather like a woodgrain. The panels are effectively lit by natural light from outside during the day and by the building’s lights during the night.

Fujikawa has used onyx before, on offices in the interior of the 30th floor of Canary Wharf. For the project, she personally selected the stone layers and chose the location of each panel within the facade.

The units are 3.94 metres wide x 1.26m high, and are generally of a 10mm annealed glass outer pane and a laminated inner pane composed of two plies of 5mm annealed glass. At ground level, the outer pane was in a critical location as defined by Building Regulations Approved Document N1, and it was decided to use heat soaked toughened glass in this location.

However, for the sides of doors the Regulations define the critical location as extending to 1500 mm above ground level, and 300 mm from the jambs. If toughened glass had been used for the units adjacent to the doors, they would have been optically different from the annealed glass panes used for the rest of the horizontal band. Therefore it was decided to use 10 mm annealed glass for the outer leaves around the doors. The size limit for robust 10 mm glass set by the Approved Document to the Regulations is 2.25 m x 2.25 m which is smaller in width than the units proposed. To justify the use of 10mm annealed glass in this location tests had to be carried out on the glass. Standard units were factory tested in accordance with BS 6206 to Class C, which involved a 45kg weight falling through 305 mm. Three units were tested and none of these broke, so it was concluded that this glass could be considered to be robust for the purpose of satisfying the Regulations.

Heat strengthened

The units with onyx marble would allow less light and heat to pass through, they would tend to be hotter than the normal units and to resist the thermal stresses the glass in these units is heat strengthened, rather than annealed.

2 Churcill Place was completed in 2004, and involved several parties including contractor Josef Gartner & Co UK Ltd and facade consultant Yolles. Studio U+A were the concept architects.

The original design incorporated a mezzanine floor at road level but this was ruled out due to cost. There is space for several shops on the ground floor, but at the time of writing the only occupant was Barclays Bank.

So where can processors go to source glass and stone laminates? Fiberstone, based in Lyon-Villeurbanne, France, and represented in the UK by Steven Kimber, offers glass combined with stone, usually crystalline marble or other types of stone, marble or granite.

Common applications are shower and bathroom partitions, tables, work surfaces and facades. Glass functions as a protective layer in the laminates, and the stone is 3mm or 4mm thick, ensuring that laminates are not too heavy.

Fiberstone’s bespoke bonding method is fully tested with the Building Research Establishment and French and German authorities, and is guaranteed for 10 years. The adhesive allows for different rates of expansion and an anti-UV material prevents discoloration in the stone, says the company.

The detail of the stone is highlighted when the panels are backlit. By combining different pieces of stone, it is possible to create very large panels.

Glass and metal

In the newly-opened Shanghai Oriental Art Center, China, architect Paul Andreu of Aeroports de Paris (ADPi) has created a building that is ‘bright and transparent as if by magic’, in the words of the architect.

In the words of DuPont, the company’s SentryGlas Plus structural interlayer made it possible for a perforated galvanized steel sheet to be laminated to glass to produce striking facades.

Paul Andreu says: ‘When I first conceived the Shanghai Oriental Center, one of my first thoughts was that I wanted it to glow beautifully at night.

‘We were very fortunate to find a Shanghai-based glass supplier – SYP – who could make the exact laminated metal / glass construction we wanted, comprising very large panels of laminated glass incorporating DuPont SentryGlas Plus structural interlayer, together with a perforated, galvanized steel metal sheet.

Resin versus PVB

Several glass processors we asked prefer to use resin laminated glass for external applications, claiming less risk of de-lamination. But the steel sheet is another complication.

Says Andreu: ‘DuPont’s structural interlayer has far superior mechanical properties than EVA-based thermoset adhesive film, and much better durability. The interlayer adheres strongly to metal, which opens it to a wide range of functional and aesthetic innovations.’

Shanghai Yaohua Pilkington technical director, Mr Pan Wei, said: ‘The glass construction is 12 mm heat-soaked fully-tempered glass + 1.52 mm SentryGlas Plus + 0.5 mm perforated metal sheet + 1.52 mm SentryGlas Plus + 15 mm heat-soaked fully tempered glass. The Shanghai Oriental Art Center is the first use of this construction worldwide.’

The distribution of hole sizes was chosen by the architect for solar gain reduction, as well as the aesthetics. An additional benefit is that the perforated metal sheeting also blocks out mobile phone signals – which should be a great relief to the venue’s patrons.