During the Royal Albert Hall's £66m refurbishment, performances must continue as usual – even if that means Sir Cliff Richard being wheeled in on a trolley wearing a dust mask.
This week, on the 150th anniversary of the opening of Prince Albert's Great Exhibition of 1851, another prince consort, Prince Philip, will unveil a grand flight of restored stone steps leading down from the rear of the Royal Albert Hall in London. The centrepiece of the restoration is a statue of Prince Albert, a memorial to the Great Exhibition and not to be confused with the more elaborate Albert Memorial facing the front of the hall from Kensington Gardens.

The steps and statue, however, form little more than a huge, decorative lid. What the guests at the opening ceremony will not see is the three-storey underground labyrinth that has been created directly below. Stuffed with plant rooms, workshops, dressing rooms and a vast service yard for articulated lorries, this is the expanded engine room that will make the the UK's largest purpose-built concert hall operate more efficiently and will, for the first time, introduce modern air-conditioning. The basement extension is a key part of a £66.3m package of refurbishments to the 130-year-old, grade I-listed building, which is not due for completion until 2003.

Concert-goers likewise have little clue about the extent of the refurbishment programme. For them, the show goes on as before. Last summer, for instance, Sir Cliff Richard's stage entry stunt was to appear through the stage floor in a puff of smoke. What the audience did not see was more outlandish: to reach the stage-floor hatch, Richard had to be pushed through a waist-high underground building site on a flat trolley while lying on his back and wearing a dust mask.

The show-must-go-on mentality pervades all aspects of the refurbishment, and is what distinguishes it from many other theatre renovation projects, most notably that at the Royal Opera House, completed last September. Otherwise, the two projects have much in common. Both are lottery-funded refurbishments of internationally famous Victorian music auditoriums in inner London. Both have entailed extensive backstage and services improvements to increase efficiency and comfort. Both have extended development programmes of longer than 10 years. And both share the same architect: Martin Ward, head of Building Design Partnership's multidisciplinary design team at the Albert Hall, helped design the Royal Opera House scheme as part of a Building Design Partnership/Dixon Jones joint venture.

"The big difference is that the Albert Hall is financially self-reliant, with no public revenue funding," says Ward. "It was convenient for the Royal Opera House to close for refurbishment, because it stopped running up losses for a while. But the hall cannot afford to close, because it would lose revenue and it could lose clients permanently. Certainly, we are nervous about the expense and inefficiency of working in a building while in operation, but that's the way it has to be." The hall's deputy chief executive, Heather Walker, explains the problem from the performers' viewpoint. "They had two main anxieties. The first is the dust and cold which affects dancers and musical instruments. The second is noise during rehearsals, as nearly every evening event is preceded by a daytime rehearsal. Finding moments when builders can let rip and make a lot of noise and mess has to be very carefully managed." The construction team has taken a twofold approach to these site constraints. First, construction management was adopted as the procurement route. Second, a series of Monday morning meetings was set up to plan how to keep builders and performers out of each other's way over the following week.

Bob Older is project manager for Taylor Woodrow, which narrowly beat what was then Bovis to the tender for construction manager in 1995. "Construction management is crucial to the sequencing of works so as to preserve the continuity of hall performances," he says. "We have broken down the 10-year development into 29 individual projects, each with a life of its own and worth between £500,000 and £2m. This keeps the dialogue going on manageable issues. And each project is sequenced to unlock others. For instance, retiering the seating at the south end of the auditorium allows the removal of stairs behind it, and this in turn will make way for the rebuilding of the south porch." Tenders for lump-sum contracts are invited from trade contractors separately for each of the 29 projects. Older says there are no repeat orders, except for mechanical and electrical services, where continuity has been a consideration. Stavely Services was awarded the first £7m M&E package in the basement after a two-stage tender and then negotiated a further nine contracts on an agreed schedule of rates.

Older also claims that, unlike at the Royal Opera House, "we missed out on any labour disruption", because the small, self-contained jobs were relatively easy to keep under control. "Generally, it's been a friendly project. At every milestone we have a little celebration," he adds.

The weekly meetings to co-ordinate building works and performances are held by the hall's executive committee, on to which Older has been co-opted. "We are treated like any other hall department," he comments.

The co-ordinating committee has adopted the analogy of the level-crossing. "There are all these trains thundering past, and we've got to allow all traffic to cross the rails without getting in their way," explains Older.

One of the more prestigious thundering trains is the Institute of Directors, whose annual conference was held in the building last week. The IOD would not accept that the two first-floor halls, where it traditionally holds its receptions, were temporarily separated by a void after the removal of a staircase. To connect the two halls, a temporary boxed bridge was slung across the void. "We can't turn 5000 people away," says Older.

According to Walker, the hall has closed for large-scale works for a total of only eight weeks since 1996, and no shows have been cancelled because of building works. Indeed, the hall has actually increased bookings, although she concedes that this is partly because of separate commercial ventures.

"In 1995, before we started construction, there were just 250 shows," she says. "Last year, there were 320 shows, with very healthy 80% attendances. Promoters can see that the refurbishment will benefit them, as they can unload and set up their shows more easily and quickly. We are now looking to push shows up to 350 or 360 a year by encouraging two shows a day." The doubly restored Prince Albert, beaming down on his 130-year-old creation from both front and rear, would no doubt be proud of this renewed fusion of culture and commerce.

Refurbishment highlights

1 Services basement
As is the rule in theatre and concert hall refurbishments, the £66.3m makeover of the Royal Albert Hall largely consists of upgrading and expanding the back-of-house facilities and plant. However, the grade I-listed hall is a uniquely detached structure with a continuous wrap-around facade – like the Colosseum in Rome – that offers next to no scope for extensions. Instead, the South Steps – the stone stairs leading down from the back of the hall – were removed and the underground car park below was deepened by 12 m to create three underground storeys for scenery access, air-conditioning plant, an electricity substation, workshops and dressing rooms. The undercroft directly beneath the hall has also been expanded by excavating a second concentric tunnel devoted entirely to ducting and cabling. Another much deeper tunnel was hand dug purely to serve as a low-pressure air-supply duct leading from the plant rooms to the auditorium. 2 External landscaping
The restored stone South Steps, officially reopened this week by Prince Philip, form the reconstructed lid to the new plant basements. The memorial of Prince Albert has also been restored, and its plinth has been slightly raised to double as a fire escape from the enlarged basements below. Gardens on either side of the steps have been restored in a Victorian baroque design. All roads leading directly up to the hall and its four porches will be closed off, as production lorries are now served by the underground loading dock reached from beyond the South Steps. The entire open space surrounding the hall can then be repaved in granite setts as a grand traffic-free civic piazza for concert-goers and the public at large. 3 New south porch
The only above-ground extension to the hall is the expansion of the south porch, and this project has caused one of the biggest set-backs in the refurbishment. The existing south porch is smaller than the other three, as it originally served as a link to a large conservatory, which was built for a garden exhibition in 1870 and long since demolished. The plan is that a replica of the other double-storey porches will be built on the south side, where it will serve as the main box office with offices above. The new porch has been designed in red brick and buff terracotta to match the existing hall. However, the contract for CeraFrance to supply 8000 terracotta blocks was terminated last year, delaying the project by several months. The French company failed to meet standards of colour, texture and modelling quality laid down by the architect and English Heritage, as agreed in the contract in 1999. Building Design Partnership’s project director, Martin Ward, says: “We believe there are no grounds for a claim, and after an initial letter from the supplier’s solicitor a month or two ago, we have heard nothing more.” The terracotta supply contract has since been awarded to Shaws of Darwen. 4 Auditorium remodelling
Inside the listed auditorium itself, seating in the stalls and circle has been retiered to improve legroom, access and safety. The retiering of the stalls involved replacing timber beams with prefabricated tiers containing hollow cores that serve as air-conditioning plenums. The reordering gives more headroom to the foyer below. The auditorium’s much-criticised acoustics were analysed by Dutch acoustic consultant Peutz & Associés. It constructed a 1:12 scale model – as big as a typical living room – as the elliptical geometry of the volume proved too complex to input into a computer. To provide extra sound diffusion, a classical cornice and large, scrolled brackets removed in the 1940s are being reinstated in replica around the perimeter of the dome. And as for the alien-looking fibreglass flying saucers installed in 1969 to curb reverberation, these will now be grouped towards the centre of the dome to improve acoustics. 5 Front-of-house remodelling
Four bars have been created and two existing ones extended into the side porches. Modular disabled lifts inserted into the side porches now serve all floors. The Victorian stencilled decorations in green and beige are being reinstated. In contrast, the new toilets are modern and high-tech in style – “a relief from Victoriana”, comments Ward. 6 Roof
Though not visible to the public because of an opaque ceiling added in the 1940s, the roof of the Royal Albert Hall is perhaps the most spectacular feature of all. It is in the same league as the great Victorian railway station roofs in iron and glass, with the extra ingredient of being an elliptical dome-shaped structure culminating in a dense core of criss-crossing iron trusses. The original glazing around the perimeter, which has an overlapping detail as in a greenhouse, is being replaced to match with more secure aluminium glazing bars. The roof is structurally sound, but a ring of beams is being bolted near the perimeter to support a new maintenance gantry below the ceiling.