New Bury Theatre, Hurstpierpoint College, Sussex

Introduction

Hurstpierpoint College, a co-educational day and boarding school in West Sussex, has a long tradition of theatre performance; its Shakespeare Society has performed a Shakespeare play every year since 1854. It is a tradition celebrated in the new performing arts centre designed by Burrell Foley Fischer. The theatre accommodates a variety of formats to suit drama, dance, music theatre and musical performances as well as school assemblies. It is also a highly sustainable, low carbon building, achieved by the use of a timber structure and cladding together with a natural cooling and ventilation strategy.

The college caters for pupils from 4 to 18 years and its 140-acre campus lies in beautiful countryside close to the South Downs National Park in West Sussex. The original Victorian Gothic quadrangle and chapel have been surrounded by later buildings and the performing arts centre is the first stage of a new masterplan which will co-ordinate them into a collegiate framework. It stands at the centre of the campus, the auditorium distinguished by its zinc-clad pitched roof capped with four roof ventilation chimneys and flanked by lower single-storey spaces containing dressing rooms, toilets, workshops and offices. The façades are clad with crisply detailed western red cedar boards.

The main entrance, facing the original college buildings, opens to a spacious glazed foyer which runs the full length of the east side, and is used for teaching, rehearsals and for theatregoers to meet and assemble before a performance.

The auditorium has a ‘courtyard’ format and like traditional courtyard theatres it is constructed of timber, creating a warm and intimate atmosphere. The rectangular plan has two levels of galleries set at each side and raised seating at the rear. The stage is flexible and the ground floor seats can be removed to create a raised ‘thrust’ stage.

The pitched roof of the auditorium is supported by four pairs of exposed glulam trusses, each pair set closely together so that the two bottom chords support four technical and lighting access bridges, which are accessed from the upper gallery. The trusses are supported by pairs of exposed glulam columns which also support the side galleries, which are lined with maple balustrades.

The auditorium provides an intimate theatre for performing arts activities and, with a seating capacity of nearly 370, it accommodates school assemblies in two groups. It has also been made available for use by local groups with whom it is very popular.

The choice of timber

To fulfil the acoustic and structural requirements of a small theatre which would also be environmentally sustainable, the clear choice was timber. The practice had previous experience of designing with CLT (crosslaminated timber) and glulam, as Geoff Pyle of Burrell Foley Fischer explains: ‘We knew that as a structural material timber was capable of being used to create an excellent theatre space. We also knew that it would offer a visual feel and aesthetic that would be well suited to the project. The timber would provide a degree of natural thermal insulation, and being in panels it would be simpler to form an air-tight seal for higher thermal performance.’

As well as its integral environmental advantages, the practice appreciated the cost and speed benefits of off-site timber fabrication. The exposed glulam frame and CLT wall structure could be quickly and easily erected on the concrete undercroft (used to cool external air naturally before entering the internal spaces). Services could be coordinated using the BIM computer model and the manufacturing process of cutting in the factory would mean that holes and cutouts would be provided as drawn, avoiding site errors and tolerances inherent with other materials. Erection using a single crane could be achieved in a relatively short period.

For a theatre building the practical advantage of a timber structure was the ease of installing theatre lighting rigs, technical stage equipment and access decks. These were designed to be fixed to or hung from the timber structure and, once on site, were installed relatively simply and quickly. This gave the contractor reassurance and reduced the risk of errors.

The timber structure

Rachel Pattison, structural engineer and associate at Price & Myers, describes the structure: ‘The glulam roof trusses, which span more than 10 metres, are designed to support the CLT roof panels and the technical access bridges. The geometry is designed in a way to provide clear access for technicians to operate lighting equipment and as such do not have any diagonal members. The bottom chord of the truss works in combined tension and bending from the truss forces plus torsion due to the offset technical bridge support slab. Headroom was critical around the perimeter at the access gallery and as such the truss has been designed in a way which results in a shallower timber member between the column and external wall. This section of the bottom chord is acting as a tie between the end of the roof panel and column to prevent horizontal forces on the external CLT wall.

‘The lateral stability of the building is provided by solid CLT wall panels. These act as cantilevers from the substructure and work in bending and shear to transfer the lateral loads to the foundations. The walls are typically 95mm thick CLT and, as shear walls, the forces are well distributed and the panels are not overstressed.

‘The grid of columns is largely defined by the number of technical access bridges and their width. The three access bridges are 1350mm wide and are set 3175mm apart. This creates the column arrangement and provides the support for the essential equipment to operate the theatre during performances.’

The CLT walls and cedar cladding

The 95mm thick CLT wall panels are generally clad with an insulated rainscreen of untreated western red cedar boards, used in both horizontal and vertical format. The vertical boards are set in a sequence of 102, 122, 102 and 82mm widths. They are tongued and grooved with a 4mm V-joint and are secretly pinned to battens. At external corners the joints are mitred to a Y-shaped purpose-made 5mm stainless steel vertical trim which is fixed at each side to the battens. The bracket creates a crisp edge, especially at the junctions of horizontal boards, and provides some physical protection on the external corner.

Sustainability and energy use

Instead of conventional mechanical ventilation and cooling with its associated intensive energy use, the auditorium is naturally ventilated. Fresh air is delivered and heat extracted using the natural buoyancy of air combined with an extensive concrete undercroft below the building which cools incoming air. Four ventilation chimneys on the roof of the auditorium allow stale air to exhaust to outside. The combination of these design measures results in a calculated energy consumption of 64kWh/sqm per annum compared with 78kWh/sqm for a notional typically designed building of this type.

The benefits of timber

Burrell Foley Fischer summarised the advantages of timber compared to steel or concrete:

  • Embodied carbon in the timber itself, a major ‘plus’ for the environment.
  • Off-site manufacture results in a clean construction site, fewer wet trades needed, minimal dust and fewer safety risks.
  • Fewer deliveries (lower carbon and easier to manage). The whole of the timber structure was provided in only seven deliveries.
  • Faster construction. The build period was compact at eight weeks. Concrete would have taken much longer. Steel would have required cladding and protection, taking time.
  • Lightweight structure (compared to reinforced concrete) reduces foundations and transfer structure at ground floor level, saving time and cost.
  • Ease of integrating and co-ordinating postfixed services such as lighting rigs. Fixings to timber are simpler than to concrete or steel.

Awards

Structural Timber Awards 2020 – shortlist
Wood Awards 2020 – shortlist
Sussex Heritage Trust 2019 – Public and Community Award

 

Prepared by the publishing team with contributor Susan Dawson.

Completion Date:

May 2019

Building Type:

Performing arts centre

Location:

Hurstpierpoint College, Sussex

Architect:

Burrell Foley Fischer

Structural Engineer:

Price & Myers (CLT and glulam structure)
DOA

M and E Engineer:

P3r

Theatre and Acoustic Design:

Charcoalblue

Main Contractor:

Management and Construction Services Ltd

Structural Timber Supplier and Installer:

KLH UK Ltd

Joinery:

T J Lowery, SB Joinery

Timber Supplier:

Wenban-Smith Ltd

Timber Elements:

Structure, roof, walls, staircases, handrails and balustrades, internal linings and acoustic panels, external cladding

Timber Species:

PEFC-certified Austrian spruce, western red cedar, maple, poplar

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