The first phase of the Paddington Central development is racing towards its July 8 completion date, helped along by extensive use of modularisation. But the underlying partnership of the construction team has been equally influential.
We're still in our honeymoon period," says Pat Carroll from Bovis Lend Lease. This is how he describes relations between the main contractor and the m&e subcontractor on the £85 million Paddington Central development. This is an unusual situation given there is less than five months to go before the first phase, of what is London's largest mixed-use development, is due for completion.

But it doesn't end there. Relations between all parties throughout the design and construction have been positively upbeat. So what's the secret? In services terms the scheme is relatively conventional, made up predominantly of Category A offices arranged over two 11-storey blocks (see box story). But what is less conventional is the route taken to bring it all together. "The client was sick to death of the traditional type of problems that present themselves when it comes to m&e, be it in the procurement, the deliverables or the final product," explains Richard Hansen of m&e consultant Oscar Faber. "He was instrumental in saying he wanted to go about the main contract in a different way, so that manifested itself in the way we procured the m&e."

The client, Development Securities, was keen to embrace a more inclusive and open approach to the project as a whole, and to help deliver the design and the procurement processes it drew up a strict cost-plan. As an incentive to achieving this the contracts for the main contractor and the m&e sub contractor had a shared risk reward element written in, thereby giving them a share of any savings made – or any over spend.

The team
Bovis Lend Lease were appointed main contractor on a JCT 98 main contract, heavily amended to reflect its construction management role. At around the same time that the selection process for the main contractor was going ahead in April 2000, the client and design team were also inviting submissions from m&e sub-contractors for the £17 million services package.

"The issue of prefabrication came up," explains Richard Hansen, "as the client was keen to bring in the advantages this offers in terms of certainty of delivery, cost and health and safety."

Three major m&e contractors were identified as having the necessary experience in modularisation and, following informal discussions, were invited to enter a two-stage tender process. "We wanted to hear about their approach says Hansen, and importantly who their team was for delivering the project. We were looking for people who could take a collaborative approach in the development of the design."

Haden Young were subsequently appointed, based predominantly on its proposed team; its approach to modularisation and meeting the target cost plan. Frank Conolly from Haden Young explains: "We gave them what we believed they needed to make the job go the way they wanted. We brought the supply chain in very early in the process and got them involved before we were even selected to go forward."

Collocation
In parallel to the appointment of the main contractor and m&e sub-contractor, Oscar Faber were advancing with the scheme design. However to save time and accelerate the design process the production of Oscar Faber's construction drawings and Haden Young's installation drawings were integrated into one process. "It was recognised that we needed the contractors early input to get the maximum benefit from the prefabrication," says Hansen.

In September 2000 the Oscar Faber design team relocated to Haden Young's Watford offices to develop the m&e design, while the architect's team and the structural engineers moved into the site project offices, as they became available in October 2000.

Frank Conolly explains: "By working with Oscar Faber here we could tell them when they had put enough information onto the drawing to allow us to go on and develop it, and if there's any queries the design team are all together to resolve them." Connolly estimates that this has reduced the procurement process by around three months compared to a traditional route.

However both Hansen and Carroll agree that there is room for improvement on the way the collocation worked, as although the Oscar Faber and Haden Young arrangement worked well it meant Fabers were remote from the rest of the team. "We lost a bit of communication with the design team as a result of that," says Carroll. "If we could have collocated everybody from the start the benefits would've been well worth it but the practicalities are difficult to do," he adds.

The Haden Young and Oscar Faber teams relocated to site in December 2000, with Fabers joining the architects and structural engineers. Haden Young moved into their own site offices, "Initially a lot of the people involved in the design and development went down to site," says Connolly. "Over time the team changed as the design moved towards completion more of our operational engineers were involved, thus allowing a smooth transfer of the project knowledge between the design and construction phases eliminating the hiatus which occurs with the traditional approach," he adds.

In parallel with the design exercise Haden Young were procuring the primary sub elements of the m&e package. It was also decided to make the option of converting the m&e package sub contract to a guaranteed fixed price available – having completed a risk review. This meant that if the tender was brought in below the target cost plan Haden Young received a third of the risk/reward share with Bovis Lend Lease and the client. "Because you've done so much work up front you've got a much greater knowledge of the job and the uncertainties have been removed," says Connolly.

Modularisation
Modularisation has been used for the high-level horizontal services distribution, the mechanical and electrical risers, rooftop plantrooms and toilet assemblies. "It's not quite as flexible with respect to change," says Hansen "It's bringing that no change date forward. But saying that if the job is well designed it's got an inherent amount of flexibility in it anyway."

The high-level horizontal services have been brought into two main spines on each floor. These are made up of 6 m long modules which incorporate the mechanical pipework, lighting control unit, and busbars for the lighting and fan coil unit power.

"We had four weeks a floor allowed for the first fix and it was done in a week," says Carroll. "We almost had to slow down because we were putting it up faster than they could provide building to put it on."

The air side fan coil units were brought to site with the controllers already fitted and commissioned, with the intention of connecting these to the modules using flexible plastic pipework to minimise on-site fabrication. However the pipework proved insufficiently flexible. "Eventually they had to abandon it and use copper which is a shame because it was a good idea," says Carroll. "We'd still like to come up with a better idea for doing the final connection because the copper pipework is time consuming," he adds.

The final pipework connections to the riser also proved slightly problematic, as they ended up over one of the few areas of plasterboard ceiling – in the toilets – making the final site measured connections awkward. "As it turned out the design of the building didn't leave us much option," said Carroll, "so that's one lesson for the future."

Falls are the biggest killer on-site and the prefabrication of the risers has helped in this respect. Manufactured in three sections which were simply lowered into the shafts, the risers incorporate all the pipework, and importantly the access gantries, making the riser immediately safe. "You remove a big potential area for falling," says Carroll. "It's proved its worth."

There were cost penalties involved with this approach as the access gantries also act as fire stops and everything needed to be mounted on a self-supporting steel frame "We managed to transfer some money from the builders work elements into Haden Young's package," Carroll explains.

The rooftop plantrooms were a departure from the norm. At the time Haden Young became involved the design team hadn't decided how the plant would be mounted on the roof. A number of options were looked into, including plinths to sit the pipework and plant on, as well as running a floating concrete slab over the roof – which proved too expensive.

Hadens developed a modular solution that incorporated the support steelwork with the services distribution, allowing a large chunk of the distribution to be fabricated before the roof structure was even in place. This was then lowered onto upstands built into the roof.

"The procurement of that didn't go as well as we would've liked, because it was perceived that it would be part of the steel structure and priced in with the initial steelwork package," says Carroll. "But fairly quickly we realised that wasn't going to work because of all the major pipework distribution underneath it. We ended up with a package transfer out of the steelwork package into Haden Young's package." Modularisation also extends to the toilets, with the cistern, pipework and connections, being made-up on frames off-site

The future
With six months to go and the building still not fully closed off commissioning is about to start. "We've already agreed and signed off the software and graphics for the bems and again in my experience that is a novelty at this early stage of the job." says Carroll.

Several more phases are planned for the development meaning there is potential to make more of the partnering. "It took us a period of time to develop the relationship, but I believe the time frame at the pre-construction phase can now be reduced because we know each other and we've got a fairly detailed knowledge of what the client is looking for," says Connolly. "Motivation is not an issue on these sort of projects, it is less to do with modularisation and more to do with the teamwork that underlies it," he adds.

Facts and figures

The £700 million Paddington Central scheme will eventually provide over 176 000 m2 of mixed-use space. The development occupies a former goods yard just north of Paddington Station, which is enclosed by the Grand Union canal, the A40 as well as a railway line. The first phase of construction comprises 48 000 m2 of commercial, residential, retail and leisure facilities. Arranged over two 11-storey block, the Category A offices occupy the upper nine floors, with the two lower levels providing space for car parking and plant rooms. The blocks are joined by a two-storey podium structure housing the retail and leisure facilities. Building one has a gross internal area of 21 057 m2, with cooling provided by three roof-mounted 790 kW, R134a air-cooled chillers. Three 1000 kW boilers provide lphw. Building two has a gross internal area of 16 220 m2 and is serviced by two 970 kW, R134a roof-mounted chillers and three 720 kW boilers. Phase one is due for completion on 8 July 2002.