Take Trent Concrete. It offers job security and a career path, regularly takes on school leavers, and is committed to training all its 160 factory workers to NVQ Level 2 over the next few years. Staff turnover is virtually nil, boasts Mike Downing, Trent's managing director.
But construction can profit from the labour force's voting with its feet for factory work. Transferring processes from site to factory not only solves skill shortages, it can improve build quality and speed up the programme.
In the building of the Great Western Hospital in Swindon, an M4I demonstration project for sustainable construction, Trent has helped Carillion achieve the key Egan objectives of efficient use of site labour, an accelerated work programme, and a reduction in the amount of waste produced on site.
SUSTAINABLE STRATEGY
Carillion set a sustainable construction strategy for the project, which wasn't just about saving the planet. The company signed a 30-year private finance initiative (PFI) deal committing it to build the Great Western in three years and then run the building for another 27. Given its PFI obligation to maintain the hospital for a generation, the constructor had good reason to make the building as sustainable as it could, using materials and construction techniques that would reduce waste and prolong its life.
Although the architect originally specified masonry for the external walls, Carillion ruled out a brick facade because laying bricks would have been expensive and time-consuming. It decided instead to clad the Great Western in precast concrete, partly because it fits in well with the Portland stone common in Wiltshire, but mainly because it would do away with external scaffolding.
Scaffolding on the five-and-a-half-storey building would have been hugely expensive, adding several hundred thousand pounds to project costs. "That's dead money," says Paul Dempster, Carillion's senior project manager on the Great Western.
Expense wasn't the only reason for dismissing scaffolding. "It always stays up longer than you want," says Dempster. "It also means you're into safety issues, and having to work in all weathers raises quality issues too."
Carillion accordingly chose the modular, precast route. Dempster dismisses metal cladding as cheap and cheerful. "Precast is just so easy," he says. "It'll stay there for 60 years. Brick is cheaper, but you'd never get the labour on a job this size, and it would mean expensive scaffolding and slower enclosure."
Not surprisingly, Downing also weighs in against metal cladding. He claims concrete is cheaper than aluminium and glass curtain walling because concrete can span from column to column, allowing it to dispensing with intermediate structural support. Downing costs precast concrete at £230 per square metre compared with £450 for a square metre of aluminium curtain wall.
The sustainable benefits of precast cladding included less dust, less noise and less traffic on site. Management benefits included fewer people and materials on site. "It's a clean site anyway," says Dempster, "but precast helps. And once it was on, we could get straight on with paving up to the walls. With scaffolding, you can't progress your externals."
For its £1.7m Great Western contract, Trent manufactured and erected 7,600m2 of external cladding. With a maximum size of 7m by 4m and a weight of seven tonnes, the reconstructed stone panels were made as large as practicable. This was done to reduce the number of crane lifts, joints and components required, speeding up construction, and improving insulation by offering fewer points for air leakage.
WORKING TOGETHER
Unlike the site, the factory environment permitted the panels to be held in safe storage areas until they were ready for trucking out. Once on site, a single movement from a crawler crane lifted each panel into its final position on the building in a matter of minutes. Trent staff —working behind a safety rail on the hospital floor to which a panel was being attached — would then make final adjustments before fixing it.
Trent was appointed cladding contractor over a year before starting on site, and was working with Carillion even before the constructor signed the project contract. This allowed it to have a major input into the design process.
Downing believes that most designers pay little attention to sustainability. "The earlier the appointment, the bigger our impact on a project," he says. "Usually, we're appointed too far down the line. When the design's at an advanced stage, all we can do is price the job."
Just as Carillion drew up a sustainable construction programme for the Great Western, so Trent drafted a sustainability plan for its own part of the project, covering more than 30 areas. Procurement was part of the drive. Trent made sure that orders for raw materials were placed in bulk and in full loads, so fuel wasn't wasted in transporting half loads. This halved the number of deliveries by lorries with raw materials.
TURNING GREEN
Trent turned as green as it could to achieve Carillion's construction goal of sustainability. One big change was to get much better use out of the timber cladding moulds the concrete was cast into. "You'd be astonished how few cladding units repeat themselves," says Downing. "It's an average of three in a typical commercial structure." Careful design of the cladding panels helped Trent to improve mould repeatability for the Great Western job to 30.
To minimise work on site, Carillion also made Trent responsible for delivering the cladding panels with window frames, glazing and insulation already fitted.
Although not a first in construction, providing completely finished panels was a first for Trent. After casting the panels, Trent stacked them up in 'toast racks' for a window specialist to put in the aluminium frames and the glass and inspect the jointing of the frames.
In fact, there was little danger of damaging the windows and window frames by fitting them at the Trent factory, because concrete panels don't flex. And despite the high risk of accidental damage to the glazing when the panels were erected, all the window panes survived installation intact.
"Putting the windows in off site gave us a quality product," says Dempster. "It didn't matter if there was a wind howling. Installation wasn't affected and it took out a huge operation on site."
"Central to the Egan Report's recommendations is prefab construction," says Downing. "The industry is going at one hell of a lick. From a cost and programme angle, it makes things more certain and it reduces the accident rate."
In the final hectic weeks of construction before the hospital is handed over to the customer on 5 November, Dempster too can still find time to rejoice. "Looking back, we got it right," he says with satisfaction. "As long as Trent got what it wanted — the right design information — it was able to deliver what it knew we needed."
Source
Construction Manager
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