Absolutely prefabulous

Ten years ago, before a stone was laid, Sir Michael Hopkins' design was heavily scrutinised by the Royal Fine Arts Commission which demanded many changes to make it fit in with its historic Thamesfront site between Pugin's gothic Palace of Westminster and the turreted Norman Shaw building to its east. Even now, the design is controversial with MPs branding the building too dark and heavy looking.

Procurement of the building caused a stink when in November last year, cladding subcontractor Harmon successfully sued the House of Commons for not picking subcontractors fairly. The client chose a joint venture between Alvis and Seele for the cladding package instead of the lowest priced Harmon bid. Judge Humphrey Lloyd branded project sponsor Andrew Makepeace's evidence "disingenuous".

And tabloid outrage was prompted when it was revealed the building would cost £1.2m per MP. Even though the building is designed to last over 200 years.

Now, as contractors race to finish the project before the House sits after summer recess in October, the project is being reassessed. The building is being finished earlier than most critics forecast and it is being completed within a revised budget that was severely increased when delays to the Jubilee Line Extension station below lead to a 12-month delay in construction.

Problems stitching the concrete

Problems with stitching the giant concrete sections of the building together and delays in the prefabrication programme lead to the Parliamentary Accommodation & Works Committee predicting that the project would not be ready for occupation until 2001. Now, says Laing Management project director Simon Harding, MPs will start moving in during September.

Costs have also been kept under control. According to Laing's figures, the estimated cost in 1993 at the start of the contract was £216-£227m. That's £125m for construction costs, £21m for fees, £19m for risks and £51-£62m for inflation.

As Laing approaches practical completion, it estimates final costs of £235m. This assumes an original cost of £221m plus £4m for client changes and £10m for the delay caused by the Jubilee Line Extension project.

It seems remarkable that despite these problems, Harding and his team have succeeded in producing what the client wants, when it wants it. Harding, who took over as project director in 1998 from Phil Brand (who came in for heavy criticism from Judge Humphrey Lloyd) attributes part of the success to resilience. He says that even after the Harmon case ruling, which Harding still finds hard to credit, morale in the management team stayed high.

From a technical point of view, Harding's toughest challenge throughout the project has been tolerances. "We've got huge precast arches [see diagram right] which hold the building up that had to be built to plus or minus four millimetres," he says. The problem is that the building is largely prefabricated. So there are few bespoke elements to take up any slack." By the time we hit the sixth floor we had to work very hard at making the joints line up," says Harding.

While extensive prefabrication has been a concern, it is also the biggest reason why construction has gone smoothly. Portcullis House is a kit building and sequencing is planned well in advance. Almost all of the building was prefabricated, he says. The structure consists of precast arches and special floor planks that have a curved underside that forms the ceiling of the floor below.

The services have also been heavily prefabricated. Panels, measuring 3.5m by 2m, for the raised access floor arrive with service ducts attached and cable trays attached. As each panel is laid the services snap-fit together. Installation could not be simpler and fewer mistakes are made, says Harding.

Installation was further simplified by services contractor Crown House Engineering which provided a 3D viewing suite for the project. Here installers could view Portcullis House drawings on a 3D computer model. Harding says that this was a great success not only for the services installers who had a better understanding of what they were doing but also for the trades working in conjunction with the services who could see how their work affected the services installation.

The high degree of prefabrication and long planning period - Laing was originally appointed before the Jubilee Line Extension was approved - meant that construction has been fast. Constractors started working up from the concrete roof of the tube station below in January 1998 and 30 months later, over £200m has been spent.

But handover between the two projects was not smooth, explains Harding. "It was fraught. The Balfour Beatty-Amec joint venture hadn't finished working on the station so we had to start working around the edges." He adds: "It was really difficult to get a clean start".

Suprisingly, Harding says that working above another giant scheme that is run by another contractor was not a problem. "London Underground Limited and the House of Commons worked out a rulebook for running the projects together and we came to forge close links with the joint-venture team," he says. Even with 550 men on site, including 18 Laing managers, Harding claims to have avoided any disputes with the joint venture.

Now everything looks likely to run smoothly to an official opening in February. Even the MPs have decided which offices they will have. It seems Labour - as befits the current political top dogs - will take the fifth floor. The conservatives will take the fourth floor. The third floor will be split and the second floor will also be Labour.

Even the problem of the too dark roofline looks likely to be solved. Harding says that the Aluminium/Bronze roof metal will be scoured to give it a lighter colour in some areas.