Backstage: How to install a flytower – while the show goes on below
The problem of presenting evermore technically demanding shows is faced by many of our older theatre buildings and the independently owned grade II-listed Shaftesbury Theatre is no exception.
Having completed work to the auditorium and the outside of the building, which had begun in 2005, the latest phase included a new flytower and office space to be completed in time for the opening of its current show, Motown the Musical.
In the 1960s, when a counterweight flying system was installed, the safe load rating of the 1911 timber grid was increased by more than 50%. In the 1980s it was further reinforced to double that rating and for Hairspray additional temporary reinforcement was required. But the increasing demands of musical productions meant that if the theatre was to be able to accommodate them, a radical long-term solution would be needed. The current design by architects Bennetts Associates extended the height of the fly tower by 10 metres above the existing roof and massively increased the weight capacity to 35 tonnes.
Like many West End theatres, the stage is below street level by about three metres and the substage a further three metres below that. This was significant, given the nature of the planned works, and it was helpful that a survey of the land beneath the theatre had already been carried out by Crossrail.
The Shaftesbury’s chief executive James Williams explains: “In January 2013 over an eight-week period the basement of the theatre was opened up and 88 piles driven 26 metres into the ground to create four foundation caps in the four corners of the sub-stage. These would support four columns of steel from the basement through the stage area to the roof and each able to carry 200 tonnes. During the process we also began a strip-out of redundant machinery and wiring to leave the building in a state appropriate for modern staging. It was a hair-raising moment with the works happening so close to the Thames water table and with much mud and water flowing into the area, which, by early March, had to be back in use for performance.”
Over another eight-week period, as a preparation for the remainder of the construction programme, the columns were taken to roof level and part of the old stage grid dismantled. A temporary grid was built and, as Williams notes: “This was designed to separate any work in the next phase from the functionality of the building. We could build and still present full-scale shows.”
In June 2015 a heavyweight steel structure was placed on top of the four steel columns. Over a series of Sunday nights, pieces of steel, often weighing almost seven tonnes, were lifted into place and bolted together.
Williams describes the process: “With the steel frame in place, construction continued in earnest, working to very tight deadlines dictated by the intense production schedules on stage. At no point was a performance halted and it is a testament to all that business continued as usual throughout. It was only after the last performance of The Illusionists in January 2016 that the old roof was removed and the new grid opened up to the stage. Within a fortnight the original roof structure and grid were removed and the new system was connected to the counterweight cradles on the stage left wall.”
One of the challenges was to preserve the last remaining fully operational, openable roof panel above the auditorium. By cantilevering the extended flytower over the auditorium roof, it has been possible to retain this, and the rest of the flat roof above the auditorium now accommodates plant for the new air management system and new boilers.
As well as the demands of construction, the theatre’s location in the Bloomsbury Conservation Area led to the local authority requesting that the flytower exterior provide a dramatic architectural statement. The result is the striking saw-tooth box that appears to hover above the theatre roof.
Internally, the offices and production spaces created by the extension wrap round the flytower, with natural light provided by ribbon windows, angled to avoid direct sunlight. One wall is formed by the brickwork of the original flytower exterior. In the auditorium, a ceiling inspection and renovation was commissioned. A high-level working platform was installed by Unusual Rigging to allow contractors Locker and Riley access to the domed ceiling. Repairs and enhanced ceiling and lathe supports ensure that all ceilings will be fully compliant with the new regulations by the September 2016 deadline.
Spotlight: Shaftesbury Theatre
With a seating capacity of 1,378, the venue has 28 standing spaces. Behind its flat proscenium stage, the back wall of the theatre is on a slant
Depth of stage:
- Centre – 9.74m
- Stage left – 9.48m
- Stage right (down) – 9.13m
- Stage right (mid) – 9.43m
- Stage right (up) – 10.46m
Proscenium opening: 9.75m
Height of proscenium: 8.96m
Bottom of pelmet to stage floor: 6.75m
Void drop points to auditorium floor: 13.2m
Stage floor to auditorium floor: 1.17m
Height of grid: 19.1m
Flying height: 15.42m
Grid loading information: 35 tonnes in total, spread evenly over the three bays between bars 1-10, 11-23 and 24-35
Counterweight bars: 35 at 0.20m centres
Length of flying bars: 12m
Maximum load: 250kg on cast iron gas barrel. All heavier pieces must be directly flown
Height under fly floors:
- Stage right – 7.44m
- Stage left – 7.40m
- Under storage beams stage left – 6.88m
Client: Theatre of Comedy Company
Chief executive: James Williams
Head of stage: Jimmy Quinn
Chief electrician: Peter Goodman
Architect: Bennetts Associates
Project manager/contract administrator: GVA Acuity
Structural engineer: Mike Jackson, MJ Consulting
Services engineer: E3 Consulting Engineers
Principal contractor: Fabrite Engineering
Acoustic consultant: Gillieron Scott Acoustic Design
Building control: Approved Inspector Services
Fire engineer: The Fire Surgery
Specialist contractors: Emplan, Unusual Rigging, Bradbrook Electrical Services, Sheridan M&E, Locker and Riley
Motown the Musical is playing at the Shaftesbury Theatre, booking until October 2017