Tall Order

To call it a refurbishment would be somewhat stretching the context of the word. It's more of a rebuild. Britannic House, the old headquarters of BP, and a fine example of the drab, faceless, box-like office block that plagues Moorgate in London, has been stripped back to its concrete skeleton and completely redeveloped.

This mammoth task includes the demolition and rebuilding of the top two floors of the 36-storey block, the extension of the floor plate on all storeys and the redesign and reinforcement of the five-storey basement and foundations.

Some would say that it would have been easier to knock the whole thing down and start again. The client, Wates City of London Properties, considered it but a limited timescale and the risk of the City planners imposing height restrictions lower than that of the original tower rendered it non-viable.

And so, what will be the City's largest commercial office building is being resurrected from the bones of its previous incarnation to create City Point. The extension of the floor plates – 1 m on the east and west elevations, 3 m on the northern and 7 m on the southern – plus the construction of a completely new seven-storey office block at the tower's base provides a massive 75% increase in the building's lettable floor area, from around 30 000 m² to 52 700m². Add to that the top floor restaurant and a basement health club and it is a massive job.

In the midst of this colossal £160 million project, as always, is the m&e contractor. In this case it is Matthew Hall. The contractor's package is huge, somewhere in the region of £44 million. Within Matthew Hall's remit are m&e services to the core of the building – the major plant rooms and all main service risers. With this task comes the responsibility of calculating the loads and the selection of plant needed to achieve the parameters specified in a preliminary design by the consultant Foremans. As the building has developed, Matthew Hall has had to gain approval for each element of the installation from the structural engineer who decides whether the building will accommodate it.

This type of working may sound a little out of the ordinary but City Point has presented quite a few challenges for the project team. The building's sheer size means that plant rooms have had to be positioned on three different levels: in the basement, floor 14 and floor 36, each feeding a third of the building. These, in turn, are fed by a 9 MVA supply from London Electricity in the form of two Solkor rings. The huge power requirement has meant that electricity is distributed to the plant room substations at high voltage to avoid power loss. And physically fitting the services into the structure is no mean feat. Services runs couldn't be finalised before coming to site. "It was just something that you had to sort out as you came up against it," says Ray Shaughnessy of Foremans. "This was one of the reasons for the air conditioning being designed around a four-pipe fan coil system. Because of the building's structure, numerous small risers are used, as opposed to one large one, making the services more flexible than they would have been otherwise."

Add to these obstacles noise restrictions that would keep your average librarian happy (noisy works are only allowed between 8-10 am, 12-2 pm and 4-6 pm on a weekday plus no noise at the weekends) and the discovery of a huge lump of old concrete in the way of the foundation reinforcements and you've got quite a job on your hands. Plus the client has pre-let office space so the tenants are waiting to move in.

Scheduling of works has been of paramount importance on the project. The programming of services installation throughout the building has been entirely dependent upon the installation of the large plant in the three plant rooms.

Much of the work on the services has been carried out off site. Pump sets have been fully assembled remotely before being delivered to site on large skids. Once on site, the sets were positioned and the final connections made. The electrical services came in for the same treatment. Distribution boards have been factory assembled, rather than fabricated on site, giving a higher standard of workmanship and a guarantee of quality.

Matthew Hall has also had to co-ordinate all builders' works within its contract. Again this means scheduling to tight deadlines and working with the consultants to pass elements of the works as and when they are encountered.

City Point will be, when complete – and completion is not too far away, tenants begin occupation in August – one of the City's premier commercial office buildings. From the subterranean health club to the skyscraping restaurant, all clad in glass, the building will exude quality. And that goes for what is behind the scenes as well as that on show.Prices M&E installation £44 million Total construction costs £160 million