Mason, a Crown House director, is also confident that the consultants will find few defects with the completed scheme. “The snagging has been completed on one floor so far,” he says, “and the only glitch was one over-long fixing supporting the services.” The reason behind this on-site performance is that the heating, cooling and electrical services were delivered to site as preassembled modules. Most of the work was carried out at Crown House’s factory in Wolverhampton, where the company is pioneering techniques more commonly used in the car industry. Kaizen, Ishikawa and Poke Yoke sound like delicacies from a sushi bar but they refer to the quality control methods put in place by Gary Connolly, Crown’s operations manager. (Poke Yoke, for example, means idiot-proofing – designing components so that they cannot be installed incorrectly, on the same principle as the three-pin plug.) The result is a “right first time” record of 99.3% in assembling the modules.
“The plant is a manufacturing facility and not a site with a roof,” says Connolly. “As a result, our average factory productivity is well up on the site average shown by the Building Services Research and Information Association.”
Crown House first used prefabricated service modules on the refurbishment of the NatWest Tower in 1996. Preassembling the services was seen as the best way to reduce the manpower and deliveries to a congested London site. But other advantages soon became apparent: for example, the space needed for tools, plant, storage and workers’ amenities was reduced.
The mixture of production-line techniques and prefabrication makes Mason confident that the Brindleyplace installation will perform well. “It gives us better time guarantees by taking risk off-site, and means that the client knows how much the scheme will cost. And because the modules are assembled under factory conditions, we know that the inside of the pipework and ductwork is clean, so that reduces our commissioning time,” he explains.
How Brindleyplace was fitted-out
More than 230 modules have been installed at Brindleyplace. Each is built around a fan coil unit that will supply heated or cooled air to the office. Connected to the fan coil are pipes; one set delivers hot water to and from the unit and the other supplies chilled water. A drain removes any condensation. Ductwork, which will carry fresh air, is also fitted, as is the electrical wiring that will supply power to the offices. At the front of the unit, a basket was incorporated to carry the control wiring to the fan coil units.
The modules were assembled in Wolverhampton in lengths up to 40 m, each corresponding to one side of an office floor. Threaded joints connected the pipework between modules and modular wiring allowed the electric cabling to be installed in sections. When the assembly was complete, the pipework, ductwork and electrics were tested for leaks and performance before the assembly was split into manoeuvrable 8 × 3 × 1 m modules, which were delivered to site by lorry on a just-in-time basis.
Once on site, a crane lifted them to the appropriate floor, where a wheeled dolly moved them to their final location. Installers then raised each module on a scissor lift to connect with the support hangers before joining the pipework and cabling.
Crown House has appointed the University of Loughborough to benchmark the installation. The top seven floors at Brindleyplace used prefabricated services, whereas traditional methods were used for the ground floor. Once the scheme has been fully commissioned, Crown House will know how well the two methods compare. “It’s early days,” says Mason, “but already the signs are good for prefabrication.” Kevin Hole, of project manager and QS Silk and Frasier, says: “Modularising the services has certainly been no more expensive on this project than doing it traditionally before you consider the quality of programme improvements the system gives.”
So what’s the catch?
Installing the services preassembled is not without problems. “We had to ensure that the main contractor, Carillion, thought about access to each floor,” says Mason. “In this instance, the contractor agreed to leave out a window at each level so that we could crane in the modules.”
The decision to follow the modular route also affected consultants, which had to buy into the process much earlier than on a traditional scheme to ensure that the services design was sufficiently advanced for manufacture of the modules to begin.
Connolly is quick to point out the advantage this early involvement brings. “The first thing we did was build a prototype,” he says. “We then invited the services consultant, the client, the client’s maintenance engineers and the main contractor to view the prototype and incorporated their comments before manufacture of the 230 modules commenced.”
The prototype was also tested to ensure it performed as expected. One problem the team found was that the fan coil unit vibrated more than expected. “The prototype allowed us to test various solutions before it reached site, which saved time and money,” says Connolly.
Crown House has used prefabrication on other schemes, including Portcullis House, the high-profile parliamentary building. But despite the advantages it brings in terms of quality and completion time, Crown House is the only services contractor using the method in the UK.
The reason for this reluctance to offer prefabrication – and therefore to ask for it – is simple: it requires a huge commitment of resources on the part of the subcontractor. In effect, it means getting hold of the capital to start an industrial concern from scratch. Strange as it may sound, Connolly wants other subcontractors to compete with him. “The more companies that prefabricate, the more it will be accepted as the way forward,” he says.
Another problem for Connolly is that to gain maximum benefit from prefabrication, the decision to prefabricate has to be taken early in the project. For example, at the parliamentary building, an early decision allowed structural elements to be combined with supports for the services. To increase the use of prefabrication, Crown House are putting together a design guide for engineers with the University of Nottingham.
Crown House eventually aims to provide a fully piped module as an off-the-shelf unit. The modules at Brindleyplace are the first prototype for this system, says Connolly. Soon, any Crown House team will be able to order modules by quoting a reference number. Eventually, Connolly hopes to be able to supply any services contractor with a proprietary prefabricated module selected from a catalogue. Mail-order services installation – now there’s a thought.
client Argent Estates concept architect Allies and Morrison client’s QS and project manager Silk & Frasier client’s engineering consultant Ove Arup & Partners design-and-build contractor Carillion project architect The Weedon Partnership project services engineer Hoare Lea & Partners project structural engineer Curtins building services design and installation Crown House Engineering