Strengthening the 18th century, timber-framed Corn Exchange and connecting it to an upgraded 1930s Studio Theatre were key to opening the arts centre to modern audiences
Joshua Hobson of Feilden Clegg Bradley Studios and Paul Diller, building services engineer at Max Fordham, reveal how they updated the listed buildings.
When did FCBS start work on the project?
FCBStudios’ involvement stretches way back to 2013 when we were involved with developing a future vision for the Royal Pavilion Estate in Brighton. The Corn Exchange and Studio Theatre form phase 1 of a broader masterplan.
When was the Corn Exchange built?
The grade I-listed Corn Exchange is a pioneering timber structure built between 1803 and 1808. It was one of the first Regency buildings in Brighton, erected as a column-free riding house for the Prince Regent, adjacent to the stable block – now home to the Dome’s Concert Hall. It measures 54m by 18m by 10m and as far as we know is still the widest single span timber framed building in the country. The smaller grade II Studio Theatre is in the adjoining former supper room, which was built in the 1930s.
What was your brief for this phase?
Our brief was to increase the physical and visual connections between venues to improve accessibility and commercial viability. We had to stabilise the building fabric, in particular the timber-framed structure of the Corn Exchange, which was suffering from significant decay and movement. We also had to strengthen the roof structure to allow theatre and production equipment to be suspended from it - enabling an existing floor-mounted truss to be removed to improve flexibility and the commercial offer. And there was an ambition to reduce operational energy use.
How did you approach redevelopment of the Corn Exchange
We wanted to reveal and celebrate its structure. Most of the timber frame had been hidden behind linings – horizontal painted timber boards or a plaster ceiling that was added later which masked the roof structure. Five large arched windows along the west-elevation had been blocked off and mirrored over the years. Our reference was a John Nash painting of the interior showing the building at its inception when the whole roof structure was legible and the windows allowed natural light in.
Describe the timber structure
This is effectively a timber arched beam structure, running east-west, that supports a duo-pitched slate-covered roof above. The principal arched beams are three equally sized sections that are formed using curved timbers in small lengths bolted together to form a shallow arch. There are six bays, each comprising three principal beams positioned between the window openings.
Originally the walls were thought to be solid masonry, but structural engineer Arup found that the timber roof structure was supported on a trussed timber frame in masonry cladding. On the western side of the Corn Exchange, the wall was not stiff enough to resist the thrust from the arched beams and was bowing outwards.
How did you establish the structural interventions needed?
Initially, we conducted site surveys, investigations and computer modelling analysis to determine the condition of the building.
The loft space above the arched, plaster ceiling was accessible, but there were still plenty of unknowns before works began. A lot of the decaying timber was found once we’d engaged the contractor and the plaster ceiling and wall linings had been removed.
A scaffold was erected internally so the contractor could peel back layers of the building fabric and get close to the roof structure. To repair the timber structure, damaged sections had to be cut out and new sections spliced in. Some of the historic ironwork connections and splice plates also had to be repaired. In addition, because the plaster ceiling had been laid over the arched roof structure, the exposed timbers had been painted. So once the plaster had been removed we had to strip the paint from the timbers.
The structure had to be strengthened too, to enable it to support motorised theatre trusses and to prevent the walls from leaning any further. Steel ties have been introduced to triangulate the arched trusses in five bays. The ends of each tie connect to new steelwork which is stitched discreetly between three principal rafters.
Cameras installed at each end of the hall monitored the roof’s deflection during work on it and when it was being loaded with theatre equipment to ensure that deflections were within expected tolerances.
What work was undertaken to the windows on the west side?
The five arched windows have been opened up, strengthening the visual connection between venues: the two southern windows now look up towards the Studio Theatre, the central two look into the new top-lit gallery and foyer spaces, and the northern window looks into the existing Corn Exchange foyer.
The windows were dismantled and taken off site to be repaired and reglazed with transparent glass. Another line of glazing has been introduced to provide additional fire and acoustic separation between venues. The void between the glazed layers now houses a motorised blackout blind to visually separate the spaces during productions.
Has the thermal performance of the roof been improved?
The Corn Exchange had to be re-roofed. Removing existing slates gave us the opportunity to insulate a previously uninsulated roof. An extra 200mm of insulation above the existing sarking boards forms a warm roof. The additional build-up also creates a service transfer zone, so that we could route new building and theatre services up behind the wall linings, through the sarking boards and into the insulation zone, from where they can drop directly onto the above-stage theatre truss, which helps keep the interior free of building services.
How is the hall ventilated?
Max Fordham’s Paul Diller: Originally the Corn Exchange was ventilated by opening the doors at each end. The refurbished Corn Exchange has a capacity of 505 people seated or 1291 standing, which requires a large volume of air to be distributed into the performance space using mechanical ventilation. The hall has a dedicated air handling unit with heating and cooling coils in addition to exhaust air heat recovery and a mixing box to recirculate the air in the winter, if there is enough oxygen in the space.
There was a courtyard to the west of the Corn Exchange where FCBStudios’ new foyer and gallery link building now stitches the venues together. That created a new flat-roofed area, which was out of the line-of-sight from the adjacent Pavilion Gardens, where we could house the plant.
A new single-storey basement constructed beneath the Corn Exchange auditorium houses two ventilation plenums which run the length of the auditorium. We blow conditioned air into these plenums, which are connected to a series of displacement vents set into the low-level cabinetry lining the walls of the auditorium above. The conditioned air displaces stale air in the hall, which rises and is extracted through openings in the pitched roof and ducted back to the air handling unit.
Concealed below the new north-end balcony is a 325-seat retractable bleacher. When this is in use, we blow air into the plenum beneath the seating to increase the influx volume of conditioned air.
When occupancy is low in winter, to prevent the need to run the air handling unit to heat the space, we’ve concealed fin-tube heaters, which act like mini radiators, within the cabinetry.
What has been done to the Studio Theatre?
The Studio Theatre was conceived as a supper room in the 1930s. It was later repurposed as a black-box theatre. Alongside the Corn Exchange, it has been reworked and improved with the addition of a balcony in the auditorium, stairs and a goods lift to improve accessibility, and a new mechanical ventilation system with heat recovery.
Together, the interventions to the Corn Exchange and Studio Theatre result in more comfortable, accessible and environmentally efficient venues that also reveal their history.