Bristol’s Colston Hall has played host to most of the greats. From The Beatles to Black Sabbath, Led Zeppelin to The Libertines, there are few successful bands that have not graced its stage.
From the first Colston Hall, erected on the site in the 1860s, to the fourth hall, which opened in 1951, all have managed to attract the biggest names of their time.
But the present hall, which opened to mark the Festival of Britain, is starting to feel its age and a restoration is under way. Part of the project is the creation of a new foyer in a £20 million package. It will provide access to the concert hall for disabled people as well as enhancing the facilities.
New performance space alongside offices and bars will be sited in the copper-clad foyer in the first of an anticipated three-phase redevelopment.
Contractor Willmott Dixon is spearheading the first part of the Colston Hall redevelopment plans, having taken the £20 million package procured on a two-stage NEC Option A-type contract.
“The contract form encourages early involvement and discussion throughout the project team and allows the relationships within the team time to develop,” says Brian Drysdale, managing director of Willmott Dixon’s Wales and South-west region.
Demolition waste recycled
The contractor has been on site, initially with its specialist demolition subcontractor, LA More, since February 2007, when demolition of a former Bristol City Council-owned office block, Colston House, began.
Since then operations director John Boughton and project manager Richard Jones have watched the new foyer grow from the ground up.
“Ninety-six per cent of the material that came out of the demolition is being reused in the new building,” says Mr Boughton. The Colston House building was attached to the hall and that made demolition difficult.
And if the technical issues involved in knocking down the old building and saw-cutting through the stone walls of the existing hall to provide bridged links across from the new to the old building were not enough, the Colston Hall management company upped the stakes by insisting in true theatrical style that the show must go on.
“Throughout the project it was important that the day-to-day workings of the hall carried on as normal. It has added another constraint to an already complex build,” says Mr Drysdale.
The site is bounded along three of its sides by roads. Trenchard Street marks the north-west boundary, Pipe Lane the south-west and Colston Street the south-easterly edge of the site, which falls significantly from north to south.
This fall, coupled with the fact that the underlying rock sits very close to the surface, meant that piling work was kept to a minimum.
“The rock is very shallow here. The old hall is partly built directly onto the rock itself. The last thing we wanted to do was to undermine the existing building,” says project manager Richard Jones.
With a large, reinforced concrete retaining wall running across the middle of the site providing a step in the site footprint as it falls toward Colston Street, the Willmott Dixon team turned to specialist contractor Roger Bullivant to help provide the foundation and ground engineering expertise.
“The foundations are in tension,” says Mr Jones, “We had to core through the rock and use Dywidag bars to tie back in. The ground is fairly fractured between 9 m and 18 m.”
The structural frame of the building is predominantly reinforced concrete with a central atrium stretching up six levels built using structural steel.
Reinforced concrete got the nod over structural steel for the bulk of the frame because of its better acoustic and anti-vibration qualities but, where longer spans across the roof and central atrium were required, steel was used.
“The frame is quite narrow and tall, which is unusual,” says Mr Jones. “It wasn’t the easiest frame to construct because of the amount of shuttering required. Every deck was different and needed different shuttering configurations.”
The slab spans vary between 16 m and the larger 42 m length required by the designers in the bar areas. To accommodate these spans a 350 mm-thick post-tensioned slab has been placed.
The cutting edge
One of the most difficult parts of the project has been the creation of the physical link between the old and the new buildings. Cutting through the walls of the existing building to improve accessibility has proved particularly challenging.
“The existing gable wall varies in thickness between 1,200 mm and 600 mm,” explains Mr Jones. “We used different techniques to cut through, depending on the thickness.”
Where wall thickness stayed at around 600 mm, standard track saws were used but they can struggle with wall thickness above the 600 mm mark.
At these thicker dimensions a chain saw cutter sliced through the solid stone walls. These act in a similar way to a wire cheese cutter, with a loop of serrated wire passed through holes drilled through the walls at the top and bottom of the proposed opening.
This loop is then drawn together, slicing through the stone wall as it is pulled back towards a power pack, which is set up on one side of the planned opening.
Bridges linking the two sides of the atrium are manufactured using 605 x 305 x 35 mm steel sections, installed in situ and featuring a composite slab deck. These sit on bridge-bearing pads with 40 mm of isolation between them. Because of the gently curving profile of the building these bridges vary in length between 11 m and 14 m with the heaviest section weighing in at 4.5 tonnes.
“We did look at the possibility of prefabricating the bridges but each would have weighed in the region of 35 tonnes to lift in. Logistically it was tricky,” says Mr Drysdale.
The building will be predominantly clad with a distinctive copper system while curtain walling will complete the envelope.
“The majority of work associated with the cladding is getting everything set up properly,” says Mr Jones. “We have gone for a hot rolled steel structure between the floor slabs with a metal frame. We are also using a metal decking liner for the cladding. It gives a good structure to build off.”
Mr Jones is confident that the building will be ready in time for its opening date in the late spring of next year.
“We are definitely on schedule. We are plasterboarding the internal block walls and the mechanical and electrical work has started. Some of the most challenging parts of the project have been completed and we can look forward to a busy summer,” he says.
Civic pride calls for Skilled constructors
Although the Colston Hall is well known as a concert venue and is arguably the most famous concert hall in the south-west, it is in need of major refurbishment.
The development of the new foyer to the hall is the first step in a three-stage process that Bristol City Council hopes will become part of the creation of a “dynamic venue for Bristol and the West Country,” according to the Lord Mayor of Bristol, councillor Christopher Davies.
The new foyer development marks the first stage of that work with Phase 2A set to transform the existing front of house and bar facilities by providing a multipurpose performance and conference venue.
Phase 2B will see changes made to the Grade II listed building by increasing the capacity of the main auditorium as well as replacing the air conditioning and improving its acoustics.
Willmott Dixon treads the boards
Provincial theatre work is fast becoming an area of specialisation for Willmott Dixon.
Aside from the Colston Hall scheme, the company has recently finished work to provide a new 500-seat theatre and arts centre in Newport, south Wales, and theatre projects around the country.
These include a £20 million facility in Shrewsbury, a £27 million scheme in Aylesbury and the new Central Library in Swindon – all of which are set to have the Willmott Dixon magic worked upon them.
“These sorts of projects make for difficult and complex work,” says Willmott Dixon chief executive John Frankiewicz.
“And it is an increasingly important sector for us. These sorts of project can become a catalyst for more widespread regeneration of towns and cities.”