It's all very well designing buildings with extraordinary shapes, but do the architects ever stop to consider how the windows are going to be cleaned? Well, yes, actually, they do. Thomas Lane met the specialist who worked with Norman Foster on the Swiss Re tower
How on earth is the Swiss Re tower going to be kept clean? It's capped by a glass dome, so putting ordinary access equipment on the top is impossible. Even if it was, the cradle would bang into the facade immediately below because of the building's bulbous shape. Then, dropping below the 17th floor, the cradle would be further and further from the facade because of the gradual reduction in the tower's circumference, making window cleaning impossible. And rope access is out because regulations demand that tall buildings are fitted with cradles.
These are just some of the challenges Bruce Jones has faced on this, and many other odd-shaped buildings. He heads facade access consultancy Reef, whose projects also include the entire Canary Wharf estate and London's City Hall. His input affects the architect's design so he needs to step in early. "We need to get involved with the architect on day one," he explains. "It's so much easier to develop a design at this stage rather than bolting kit on later." Richard Hyams, project architect at Foster and Partners, which worked with Jones on City Hall, says: "Reef, and companies like it, have a great impact on our detailing – it's an extra level on top of our design."
Jones has to juggle a multitude of constraints when working out a solution. Architects like to have clumsy access equipment tucked away when it's not being used so it doesn't mess up the sleek lines of their buildings. Compact equipment is vital to maximise lettable space in expensive locations. Heavy plant affects a building's structure, and there are also other factors to consider, such as putting frequently used equipment speedily into working position.
City Hall was a particularly challenging project for Reef. Its weird, lopsided shape and solar control system makes facade access very tricky. External brise-soleil would have made cleaning impossible, so glazed areas incorporate a blind sandwiched between two skins of glass. Because this cavity is ventilated, the glass and fiddly louvred blind also need periodic cleaning.
Jones and Hyams started off with several access options, and narrowed these down in tandem with the facade design. "The number of different facades we went through was unbelievable," says Jones. Rope access was ruled out because the only way to clean the glass and blind in the cavity is from below because the outer sheet of glass opens from the bottom.
The final solution was to use the world's biggest cherrypicker. It has a reach of nearly 46 m, enough to get to the top of the facade. This solution had a knock-on effect on the whole design as it required an uninterrupted run around the entire building; this area, and part of the floor slab on which the machine is kept below the building, had to be specially reinforced because of the machine's 21-tonne weight.
Cleaning considerations also had an effect on the detailing. Jones suggested seals for the outer pane of glass to stop rainwater penetrating the cavity and causing streaking. Within the cavity, the blinds slide down so the inner skin of glass can be easily washed. The blinds can also be removed once every five years for a more thorough clean. Hard-to-reach areas have fritted glass that needs less frequent cleaning, as it doesn't show the dirt. These include the top of the glazed area facing the debating chamber, and the rooflights.
More recently, Reef has been faced with a new challenge – Foster and Partners' Swiss Re tower in the City of London. After lengthy consultations with the architect and client, the firm came up with a bespoke solution. Their answer was to create a device that slides out of a hole in the side of the building on rails (see The Wrap, page 65) and can reach both above and below.
Jones says there is nothing particularly special about the equipment, despite this being the biggest access project in Europe. The machinery consists of three standard elements from different manufacturers: the garaging system, a standard access cradle on cables and a hydraulic boom – which is simply a cherrypicker with the wheels ripped off. "All we have done is merge three companies that are very strong in their respective fields to produce a one-off system that works incredibly well," he says.
Jones believes solving the access problems of even more complex buildings than Swiss Re isn't a problem. "There's enough out there already," he says. "Bringing the market sectors together to provide the solutions is the biggest challenge."
Clients approve of this partnering approach, as they do not want to be guinea pigs for untested systems. And although people might like the idea of robots because of the potential labour savings (see Techno Trouble, left), for the time being at least, it looks as if there is no substitute for the bucket and sponge.
Warren Kent: Playing Spider-man for real
The only practical way to clean some buildings is by using abseilers dangling from ropes attached to the structure. Some buildings, including the unusual Lord’s Media Centre, were specifically designed to be cleaned by rope access. Warren Kent, a window-cleaning abseiler, works for New Century, the facade-maintenance division of support services firm OCS Group. The only practical limit to Kent’s working height is his 100 m long ropes. His most elevated job is waxing the pyramid on top of Canary Wharf tower – the tallest building in the country – to protect it from the weather. Despite the stomach-churning altitudes, he doesn’t get nervous. “I’m more comfortable abseiling than using cradles,” he says. “You are relying on yourself, not what other people have done in the past.” He cites the case of workers dying because deteriorating concrete on older buildings has caused access equipment to be torn away. He says nobody has ever died using rope access with his level of skill. He has never had any nasty moments when working off ropes, although suddenly opened windows can give him a shock. In fact, it tends to be the occupants of buildings who are most surprised to see someone suspended in mid-air outside their window. “Old ladies ask us if we want a cup of tea,” he laughs. Kent says the quality of glass has an influence on how dirty a building gets. Channel 4’s building on Horseferry Road, for example, has a big atrium that stays sparkling because the glass is very smooth. So is he worried that the new rash of self-cleaning glasses coming onto the market will put him out of business? “I don’t think that will ever get bird muck off it,” he says dismissively.
No such word as ‘impossible’
The facade access on Swiss Re will be almost invisible. The trained eye might just spot two parallel tracks, one above the other, running around the circumference of the building at the 36th storey; these are the guides for the access equipment. But push a button and a Thunderbirds-style sequence will spring into action. A section of facade will swing out of the way, revealing a garage that takes up half the 36th floor. Inside will be a mini-railway siding with three different machines. The one selected will be computer-guided along the rails and out of the building, where it attaches itself to the parallel tracks. All the operator has to do is climb in, ready for work. Two of the machines are conventional cradles suspended on cables, and are used to clean below level 36. Because the building is narrower here than at its widest point at level 17, a telescopic arm supports the cradle cables at level 36. This pushes the cradle out progressively as it descends. Below level 17, where the building’s circumference decreases, the operator will stitch the cables into the facade like a rock climber negotiating an overhang. The third machine is a cherry picker without wheels; its telescopic arm will extend to the top of the dome from the tracks. Finally, there is special rescue trolley in case of problems such as power failure. Armed with a built-in generator, it can operate the hydraulic arm and cradle so the stranded operator can avoid spending a chilly night suspended in mid-air.
The Heineken approach: Reaching parts other systems can’t
The last thing occupants of Manchester’s most expensive apartments want to be greeted with as they open their windows is a view of maintenance machinery. Luckily the designer, Ian Simpson Architects, was able to find a solution. The penthouses at No 1 Deansgate are progressively stepped down the sloping roof so each occupant can see over the roof of their neighbour. It was decided to hide two access machines in two troughs at each end of the building. Each is directly in front of an apartment. While the occupants of the flats are at work, the machines rise up out of their burrows. The larger of the two has an arm that unfolds, then telescopes out to a maximum of 18.5 m. At the end of each arm are cradles that descend down the side of the building. The whole arm also rotates to reach three sides of the facade. The smaller of the two machines cleans the fourth side, and the parts of the two sides the first machine can’t quite reach.
Techno trouble: The development of automated cleaningThe team at Canary Wharf dreams of automated cleaning because of the acres of glazing it has to maintain. Several machines fitted to conventional access cradles have been tried. One Canada Square had a machine that worked like a car wash with rotating brushes. Another machine, Arcow, mimicked the action of a human cleaner. Instead of a hand, though, a rectangular box consisting of rubber strips squirted cleaning fluid onto the glass, then sucked it back for recycling. The rubber strips sealed in the fluid and would squeegee the glass clean. But both these machines are now history. The only machine Bruce Jones thinks might have potential is the Skybot. This works in a similar way to the Arcow except it retains the cleaning fluid within the cleaning box with “air knives” instead of squeegees. A thin blade of air is blasted at the facade at very high pressure. The advantage of this is that it can deal with changes of profile in facades, and it uses a camera system to see where it is going. Jones says self-clinging robotic systems have all failed. One system was trialled at BRE’s research facility Cardington but the robots fell off the trial facade during the demonstration. Jones says: “There is not a big enough market for robotics to develop it really effectively.”