Developers want to use stone but they want answers, not problems. They want finished products to appear on site and go straight on to the building, completing the building envelope as quickly as possible so the internal fit-out can proceed. NSS looks at some of the ways this aspiration is being realised.

It was only last year that the first Alsecco Airtec facade was completed in the UK, on the Southampton Regional Business Centre pictured on the right. But it has now also been used on Portsmouth ferry terminal, Corby Enterprise Centre and the Olympics retail site in Stratford, and is currently being delivered to the Wigan Joint Services Centre, the Olympics Athletes’ Village in London and Farringdon railway station.

Airtec is a panel manufactured under a patented process for putting an 8-10mm stone veneer on to a lightweight aerated clay concrete, typically just under 20mm thick. It weighs half as much as 70mm solid stone cladding or regular precast concrete products.

The product was introduced to the UK market at the Natural Stone Show at ExCeL London in 2008, and the Southampton project arose out of that.

Roughly 1,000m² of the product faced with Jordan’s Basebed Portland limestone from Albion Stone were used in Southampton, but any stone that can be hand set can be used on Airtec.

German Jura limestone was used on the Portsmouth ferry terminal and is now being used on the 3,000m2 of Airtec going on to Farringdon railway station. At Corby Enterprise Centre Oathill Gold Guiting stone is being used, in Wigan it is a black granite and on the athletes’ village it is Muschelkalk limestone.

Portland stone was chosen for the development in Southampton’s city centre because it provided the best solution for the requirements of the project, which included achieving a BREEAM rating of ‘Excellent’.

This redevelopment is a key part of Southampton council’s wider plans for the regeneration and economic development of the city centre.

The architects, Capita Symonds, wanted to achieve a modern feel while maintaining the character and appearance of the Guildhall setting, where the majority of the buildings are Portland stone.

Darren Sumeghy, from Capita Symonds, says: “The high quality stone produced a striking finish, exactly as we had envisaged, which matched the local area and was in keeping with the heritage of the site.”

The six-storey business centre will be home to the Capita Group of Companies and Southampton City Council.

The Airtec Natural Stone, as Alsecco call it, is installed to the side and rear elevations of the 5,200m2 building envelope.

Phil Wood of fixing contractors Prater says: “We recommended using Airtec Stone as we had worked with Alsecco on other projects and were assured of their professionalism and design and technical expertise.

“Our installation team worked closely with Alsecco to work through the technical challenges, including product training, at their site in Stone, Staffordshire.”

Ben Parry, commercial Director at Alsecco, says: “Airtec is unique in that it opens up scope for architects and designers, since the technical and structural constraints affecting natural stone are eliminated because of its light weight.”

Ian Robottom from Alsecco says the big selling point for Airtec is that it speeds up site work. Most of it is fitted to a Metsec (or other) lightweight metal frame and once the frame is on the building the Airtec “flies up”, says Ian.

But it is an answer to façade engineering, not the answer. There are plenty of developers and architects who want traditional hand setting or more conventional stone-faced precast concrete panels like the one pictured hanging from a crane at the top of this page. It is from Marble Mosaics and has a Leistädter sandstone facing. It went into St David’s 2 in Cardiff (pictured on the next page), helping to create 130,000m² of shopping space on two levels, 300 luxury apartments and car parking spaces for 2,500 vehicles. Marble Mosaic’s £3.1million contract covered the design, manufacture, delivery and installation of 550 precast units with a finished stone area of about 4,000m².

The spandrel panels typically weighed 8.5tonnes each while column units with stone faces on three sides were 3.5tonnes each.

Another of Marble Mosaic’s projects is the Bristol Civic Justice Centre pictured above. It was designed by Birmingham-based Associated Architects LLP with Ramboll Whitbybird using precast panels faced with Red Eichenbeuhl sandstone supplied by Zeidler & Wimmel. It was chosen to complement the brickwork of nearby office buildings. Pennant sandstone from Forest of Dean Stone Firms and Jura limestone from Solnhofen were also used to tie in visually with St Thomas’ Parish Church, also in the picture above.

The site had restricted access and limited storage, so precast panels delivered on a just-in-time basis to suit site progress were an ideal solution.

With a tower crane on site, large panels weighing up to 10tonnes and typically storey-height or grid-width to span the structural columns, could be lifted into position, reducing the number of units to be fixed and, consequently, the time it took to fix them. It also meant no external scaffold was needed, which was a consideration not only in terms of cost but also because the adjacent tower block is so close and its car park had to remained open.

Appointed by Miller Construction, Marble Mosaic Co Ltd was responsible for the detail design, manufacture, delivery and installation of around 2,000m² of stone-faced precast cladding.

But stone facing is not as popular as it used to be before the recession, says Stephen Maddalena, Managing Director of Marble Mosaics. He says the majority of stone-on-precast goes to London and for prestige developments outside of London – and there are currently not many projects like that available. “Most of the enquiries in the past six months have been for recon and brick,” he says.

The Olympic village shopping centre at Stratford mentioned earlier, where Alsecco Airtec is being used, also has 2,000m² of Realstone’s Generix rainscreen system.

The Generix system offers facade tile options in various materials in conjunction with a standard patented Techlever vertical aluminium rail and clip substructure. As well as limestone, sandstone, granite and slate, the options include terracotta, natural cedar panels, steel, aluminium, zinc, copper and stainless steel.

On the Westfield shopping centre at Stratford it is sandblasted Jura limestone that is being used. The development is on a 700acre site comprising Stratford city and London’s Olympic Park. It has something approaching 200,000m² of shopping and leisure space and 100,000m² of office, residential and hotel space. There have been 25,000 people involved in the construction work.

In Stafford, 4,500m² of Generix have been used with honed Jura on the council offices, and prisons in Scotland seem to like it. It has been used on the prisons at Perth and Shotts and a third, at Lowmoss, is on the way.

One aspect of using thin stone cladding systems that is likely to become of increasing importance is that they are considered to be more sustainable, because they use less stone and, being lighter, can be fixed to a lighter structure. That can save money and is environmentally friendly because it reduces the amount of metal and concrete needed in the frame, and a lot more CO₂ is produced smelting metals and making the cement used in concrete than it is in the processing stone.

Realstone presented Generix and its smaller brother, Genesis, as sustainable building systems at the EcoBuild exhibition at ExCeL London earlier this year.

John Nolan, the Director of the Generix Cladding division of Realstone, says: “Generix and Genesis have taken a while to take off – these things do – but are now proving very popular. Clients are finding the offer of a BREEAM A+ rating backed up by a complete library of CWCT certification and standard CAD detailing an attractive proposition. We have orders for 16-20,000m² of Generix cladding secured at the moment.”

One of the very first lightweight stone cladding systems was the aluminium honeycomb-backed StoneLite pioneered in Ireland 40 years ago and now manufactured in the USA by Stone Panels Inc.

Because it is so light (from 16kg/m2) and the coefficient of expansion of aluminium is 3-4 times that of stone, some people still question the strength and resilience of StoneLite. To combat those reservations, Stone Panels spend more than £200,000 a year testing to different standards all over the world to show how strong the panels are and to prove that the adhesive holding the 3-7mm of stone veneer to the honeycomb backing is not going to fail.

In America the panels have even been subjected to explosions that would turn a solid stone slab into rubble but simply deform StoneLite during the explosion and see it return to its flat state afterwards without losing any of its stone veneer.

These days the testing also serves another purpose – providing an argument why customers should use StoneLite rather than cheaper alternatives from China. In the UK, having an Agrément Certificate, as StoneLite does, can make all the difference.

Lee Slack, of distributors Stone Company UK, says at some point, usually when the price is being discussed, cheap Chinese panels are thrown into the debate. “We can’t compete with them on price,” says Lee, “but what I say to customers is: Look, here’s our bone fidese.” And he is happy to explain the difference between the way Stone Panels manufacture and the way others do it.

Lee says Stone Company UK are just completing a 5,500m2 civic centre in Rotherham using 7mm British St Bees red sandstone as a facing on the panels. “In the current climate this is quite useful.”

They are also producing 2,000m2 of red granite panels for a project on Jersey, where the panels are being pre-unitised on frames before going to site – something which is happening more frequently now as developers want ever more of the manufacturing carried out off-site and the time on-site reduced to the absolute minimum.

Stone Panels themselves are helping to make it easier to fix their panels by incorporating fixing plates on to the back of them during manufacture, so the panel can be fixed using TEC screws, a bracket or can even be welded. They will be included in the next Agrément Certificate.

Stone Panels are also currently producing black and white panels for an artwork project in London using Absolute Black granite and Thassos marble, waterjet cut into the designs required by the artist. The cells of the honeycomb are smaller than standard to increase the rigidity of the panels, some of which are only 8mm wide. “It is more expensive than standard panels,” says Lee. “Waterjet cutting isn’t cheep in itself.”

The icing on the cake, if the order is confirmed, is for a development in London involving 36,000m² of stone panels on seven buildings. “That will keep us going for the next 2¹/₂ years,” says Lee.

“We don’t need to find hundreds of jobs to keep busy. I said at the beginning of the year that this year would be every bit as difficult as last year and it’s proving to be so. Developers don’t build with their own money, they borrow it. And if they can’t borrow at a reasonable rate they don’t build… though having said that, some projects have come back to life… It’s still very fragile.”

One of the aluminium honeycomb alternatives to StoneLite comes from Tiles International’s Dynamic Facade, a division dedicated to façade and cladding systems that they launched in 2007. They also offer 5mm stone finishes on a 12mm granite backing to provide the extra strength cladding needs without having to make the panel the thickness that would be required if it was solid sandstone or limestone. TI Dynamic Façades used to source their stone products from Italy but these days they come from China, although the company say they deal with quality control themselves and that they have formed partnerships with Chinese companies rather than just employing a company to produce the panels for them.

The reason for developing the facade division was simple. “People don’t want to build buildings to take heavy stone,” says William Harwood, Director of Dynamic Façades. Their panels are all less than 50kg/m² and they can supply them for £100/m². “We are developing systems that can be put up by façade companies rather than stone companies,” he says, although he believes there will always be a demand for stonemasons for traditional hand-setting.

Dynamic Façades call their cladding systems Aerolite. The version with an aluminium honeycomb backing is called Ultralite and the version with the granite backing, Stonework.

William Harwood says it is only in the last five years that the stone facings have taken off. “People who didn’t touch anything like this are now using it,” he says. “£250/m² installed with insulation is very attractive.” Even so, most of their customers choose something other than stone as a finish.

Domus Façades, the subject of a management buy-out last year, say stone has suffered particularly in the downturn because high value commercial projects have become particularly scarce and architects have re-evaluated their cost centres. “There’s a lot of value engineering going on,” says Richard Piggott, the Business Development Manager at Domus Façades.

He thinks British stone faces particular problems. “Architects are trying to use local stone, but one of two things usually happens: either the quarry can’t supply it to the highly specific requirements of our rainscreens or they can’t produce it in time, so we end up using European stone.”

Since the MBO, Domus have offered a full design and install service, which is a new approach for them. And they have looked for their own cost savings, which has resulted in them having some of their frames extruded in Bulgaria, as well as from their traditional suppliers in Italy and Germany.

Stone finished projects they have carried out include Waitrose in Leeds with a Stanton Moor finish that they completed last year, Bolton College in Moleanos they have just finished. They are currently supplying apartments at Grosvenor House using 15mm Moleanos and 16mm Italian Basaltina on a eight-storey lift shaft, a requirement for which was that the cladding should be less than 70kg/m².

Stone Magnet gets a grip on cladding

Lifting equipment company GGR Group have developed a new, rotating ‘Stone Magnet’ vacuum lift specifically for the installation of stone cladding panels and commercial stone veneers.

The Stone Magnet, which is a below-the-hook device with a depth of only 292mm for use on scaffolding, uses a constant running vacuum system to lift stone cladding pieces up to 300kg in weight. There is an audio-visual low vacuum alarm system for safety and the machine features 360º continuous lockable rotation and 90º tilt from any position, so cladding units can be easily manipulated into mounting position.

The lifter, which is fully CE marked, is powered by an on-board 12V rechargeable battery with integral charger, so no cords. The frame can be adjusted three ways to suit different panel lengths and shapes for a more stable lift.

The Stone Magnet was developed specifically to improve handling of larger, thinner stone cladding panels on building facades. “We found that customers needed a safer, more efficient way of lifting larger stone cladding pieces that minimized risk of damage to the panels and themselves,” says Graeme Riley, CEO of GGR Group.

The Stone Magnet has already made its debut, working on projects such as Lancaster University, where it was able to fit between the scaffold and building envelope to lift the cladding panels into position.

It has recently been used at Liverpool John Moores University to fit 250kg composite slate-effect cladding panels imported from Dubai.

www.ggrgroup.com

Sticking to it in Scotland

Kirk Natural Stone Developments in Fyvie, Aberdeenshire, have made a business out of giving buildings a new lease of life by cladding them, or some parts of them, in stone.

The house pictured above has been renovated with new windows and rendering, but also by having the concrete cills, door frame and steps clad in 30mm Heron sandstone from Poland.

Kirk Natural Stone Developments will (and have) clad entire buildings or parts of buildings to create feature stone elements. The stone is stuck on up to 3.7m and above that also includes mechanical fixings in line with cladding standards.

The house pictured above is called Castle of Auchry Cottage in Aberdeenshire. It was bought by Martin Kirk, Director of Kirk Natural Stone Developments, speculatively to improve and re-sell. He did it because there was not enough work coming in. “It would be nice if the residential property side picked up a bit. It’s dead. It’s worse this year than last.” he says.

One project he has picked up is cladding the concrete walls of a roadway cutting in Dundee with 350m² of Chinese granite. Another involves smartening up a shopping centre in Dundee with 170m² of cladding in Dalbeattie granite from Dumfriesshire at one one entrance that is 19m high and another that is 14m high.