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Opening up the Exchequer

The UK's historic Treasury building in London is undergoing a ú128M refurbishment under an ambitious PFI scheme. Margo Cole reports

Corridors of power do exist - but not for much longer at the Treasury. The 100 year old building is undergoing a major transformation that will see walls torn down and open plan offices created as sweeping changes are made in working practices at the Whitehall department.

Refurbishment and reconstruction is the responsibility of Bovis Lend Lease, as contractor to Exchequer Partnership, which has been granted a 35year concession to operate the building and lease it back to the Treasury. The work - financed by ú128M ($186M) in bank bonds - started in July 2000 and is scheduled to take 25 months.

Staff in the 100,000m 2Portland stone-clad building have been moved into the east side while 48,000m 2of space on the west side is rebuilt in this ambitious Private Finance Initiative project. When they move back, Exchequer Partnership - a joint venture of Bovis Lend Lease, Stanhope and Chesterton - will look for finance to refurbish the other half, and find another government tenant.

Government Office Great George Street (GOGGS) was built in two phases at the turn of the 20th century. A 10-year gap between the two was taken up with delicate negotiations to persuade the ICE to move out of its newly built headquarters and relocate to the other side of the road.

The first phase was built using load bearing masonry walls and clinker concrete floor slabs, while the later construction made use of newly developed structural steel technology.

Up to six floors of offices surround a square courtyard, with a further three basement levels below.

By ripping out walls and bringing existing light wells into use, Bovis is creating an extra 40% of space within the west half of the building.

According to Bovis project director Julian Daniel, the maze of corridors, offices and small enclosed spaces deterred many of the 1,100 staff from venturing outside their own areas for fear of getting lost. The new scheme will make circulation easier, as well as turning the previously unused courtyard into a garden to create a 'focal point'. All services will be replaced, new lighting installed and a natural ventilation system introduced to improve environmental performance.

Light wells clad in traditional white glazed bricks penetrate the building, but currently offer little light. In the new scheme they will be roofed over with lightweight ETFE to turn them into usable space for a library, kitchen and auditorium. One large light well at the west end will be incorporated into a new full height entrance and reception area, which will feature glass lifts.

Rather than increasing, loadings are actually reduced with so many solid masonry load bearing walls coming down.

In all, Bovis is demolishing 12.5km of wall, some up to 6m high, and creating an open plan layout based on a lightweight structural steel frame and concrete floors. As the building is Grade II* listed, English Heritage has to approve all internal work.

Walls and floors have to be preserved where they can be incorporated into the new layout. and these are being propped as part of extensive temporary works.

Some old walls also have a structural function. While planning the job, the project team value engineered out all piling with a design that springs the new lightweight steel internal structure off the load bearing masonry. This saves money, but increases the amount of temporary works - predominantly consisting of steel 'goal posts' and intermediate props which can be removed systematically as the new floors are built back up.

Demolition contractor Griffiths McGee's ú7M contract includes design of the temporary works, but the firm is working closely with structural steelwork contractor Rowen to ensure the new steel can be taken through and fixed into place.

Bovis has close relationships with the key package contractors, says Daniel: 'We've partnered 70% of the job and negotiated contracts with the firms. They're all friends.'

This is essential on what he describes as 'a builder's building. All the solutions are here, ' he explains. 'People say the devil's in the detail - and on this job you've got to understand the detail to understand what the risks are. If you take a superficial view you'll come unstuck.'

Design and buildability are interlinked, so the project team - which includes architect Foster & Partners and consulting engineer Waterman - must be flexible enough to adapt to changing circumstances as demolition uncovers new problems.

A special feature of the Treasury building is the 'detonation slab' - a concrete slab between 1.75m and 3.5m thick that was installed beneath the ground floor slab when the Second World War broke out. Eight hundred workers were reputedly brought over from the US for the slab's construction, as pumped concrete was still new in the UK at the time.

The high strength reinforced slab, which contains 90N concrete was designed to withstand a bomb attack and allowed the government to relocate to the basement and sub-basement levels of the building for the duration of the War.

One third of the area beneath the slab is now occupied by the Cabinet War Rooms museum, which will be extended once the refurbishment is complete. For the most part, the slab is being left intact, but sections have to be cut out, for example to give additional headroom to install a new lift pit in the entrance and to create new wheelchair access.

In the circular east court the visible edge of the slab in front of the building is being removed.

Specialist firm Robore has a ú1M contract to cut out the lumps of concrete using a diamond wire cutter.

A core is drilled on either side with the wire fed through and attached to two arms of a hydraulically operated machine, which rotates, bringing the arms together so the wire slices through the concrete.

The project is just six months old but already much of the demolition is complete and sections of permanent steelwork are in place. The last few corridors are about to disappear.

On the spot

Name: Julian Daniel Age: 38 Qualifications: BSc (Hons) civil engineering, Current job: Project director, Bovis Lend Lease Best thing about current job: The cut and thrust of a fast moving major refurbishment - or doing what Hitler could not manage, as one wag stated.

. . . and the worst: The days I cannot cut and thrust fast enough.

Best job ever and why: Apart from this one, Banque Paribas headquarters behind Marylebone Station. Excellent achievement by a team who generally put the project first and needed to, on an ú85M project carried out in 77 weeks.

. . . and the worst: I am not at liberty to say, but all bad projects end sometime, even Sadlers Wells!

Most important lesson learnt in career: Only look back if it helps you move forward.

Hopes for the future: Keep a 'can do, will do' mentality until I retire (early) and be a director of (a successful) Hull City Football Club Additional information: If you lead with your chin like I do there are always lots of embarrassing stories, some of them printable, most not. I did a couple of years of morris dancing in my youth which gives colleagues weeks of enjoyment at my expense when they find out.

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