Cost study: National Agriculture Centre

<b>At-a-glance guide
New Exhibition Hall, National Agricultural Centre

Client</b>
Royal Agricultural Society of England
<b>Location</b>
National Agricultural Centre of England, Stoneleigh, Warwickshire
<b>Construction cost</b>
£3.7m for 6452 m2 gross internal floor area
Unit cost £574/m2
<b>Special design features</b>
Walk-through subway to allow access to grid of services outlets in hall floor
New exhibition hall connects with existing hall so that both can be used simultaneously or independently
<b>Cost and procurement constraints</b>
£4.5m overall budget
Construction timetable set to fit between major shows on fully working trade showground site
<b>Form of contract</b>
Management contract (JCT98) with works package contracts
<b>Contract period</b>
Procurement and construction period: 10 months Total
development period: 14 months

<b>Client brief</b>
The Royal Agricultural Society of England needed a second exhibition hall at its National Agricultural Centre in Stoneleigh, Warwickshire. The 100 ha centre is the venue for the annual Royal Show with large external show arenas and pavilions.
In November 1998, the Royal Agricultural Society asked RMJM to look at the feasibility of increasing the amount of up-to-date, purpose-built exhibition space at the showground. The intention was to market the venue to clients outside the agricultural world, in competition with Birmingham’s National Exhibition Centre nearby.
The client wanted to accommodate larger shows than were possible in its 1990-built hall, and there was also the need to stage separate events simultaneously. By linking the new hall to the existing one, both halls could be let separately or as a combined exhibition space of 7852 m2. New foyer, cafeteria, conference and administration areas were also required to serve both halls. Clear external walls were stipulated so that the new hall could maximise the lettable area for exhibition stands.

<b>Site layout</b>
The new hall has been placed to cut across the National Agricultural Centre’s gridiron of roadways and isolated plots. The building stretches across two plots lying south of the older exhibition hall, blocking off the road passing between them.
As well as preventing through-traffic, the arrangement creates distinct courtyards on three sides. Two of these are interlinked service courtyards with lorry parking, and the third is a formal, traffic-free exhibition square, providing the main pedestrian access to both exhibition halls.
The exhibition square and one of the service courtyards can also be used as external exhibition areas. When adjacent buildings become redundant, the exhibition square may be extended.

<b>Architectural design</b>
In RMJM’s design, the new exhibition hall of 4536 m2 is adjacent to and connected with the existing hall (see site plan opposite). Both halls are reached from the new exhibition square through a common foyer that provides a single point of control to the entire complex. The foyer is arranged as a double-height space with café and offices adjoining.
The new hall provides a clear, column-free, rectangular floor space 84 m long with a 45 m clear-span central area. Beyond a row of columns to one side, a 9 m wide aisle increases the overall width of the hall to 54 m. This configuration caters for standard 3 m2 exhibition stands, and also offers opportunities for increased stand sizes. The hall has an internal clear height of 8 m, giving ample provision for larger exhibits. Arena events may also be accommodated in the central space with banked seating in the side aisle.
Amenity facilities and back-up areas, including plant area, are based on occupancy figures of one person per 1 m² of exhibition space. Toilets are arranged as two pod structures with curved ends, which project from the rectilinear hall, while the plant is housed on the roof and concealed behind parapets.
The hall has a simple box form, with the ancillary accommodation adopting a lower-level, butterfly-pitched roof. The butterfly roof mirrors the low pitch of the older hall’s roof in order to create a unified complex.
Internal and external cladding was designed as a neutral backdrop for the exhibits. The exhibition hall is clad in large-scale, profiled steel cladding laid horizontally between fins at 6 m centres. The ancillary accommodation and the toilet pods are clad in glazed and composite metal panels with a common modular dimension.
The foyer is generous and adjoins the 250-seat café, which is also suitable for smaller exhibitions or displays. Although this accommodation faces north on to the exhibition square, a series of rooflights along the centre of the café allow sunlight to flood into the space.
The building is functional throughout with its component parts clearly identifiable externally. These comprise the simple rectangular form of the hall itself, the projecting toilet pods with their curved ends, and the foyer and café contained beneath the butterfly roof that projects forward to form an entrance colonnade. Finishes are simple and practical, creating a sense of space and lightness with clear orientation and order for visitors. It offers opportunities for flexible and extended uses as well as establishing a new design ethos on the site.

<b>Services distribution</b>
The hall is serviced from below for power, data, telecommunications, water and drainage by a walk-through service tunnel that bisects the building beneath the ground-floor slab. Lateral service ducts spur off the tunnel to a 3 m grid of metal-lidded outlets, which serve all exhibition stands.
The spine tunnel is accessible from the service yard behind the exhibition hall, which allows the services for the next event to be installed while its predecessor is still under way, thus saving turnaround time.

<b>Procurement</b>
The building completion date, in May 2000, was set by the Pig and Poultry Show, which needed to occupy both the existing exhibition accommodation and the new exhibition hall. Because of the timetable restriction, it was decided to use a two-stage tender management contract. This allowed the contractor to be part of the design team at an early stage and help devise the most economic and buildable solution.
The project was procured using the JCT98 Management Contract, with works tendered on the basis of package contracts. Bills of quantities were prepared for each package, which were then competitively tendered. The design process began in March 1999 and work started on site in July the same year, immediately after the Royal Show.
The management contractor, Tilbury Douglas, handed over the completed project by the set date, 10 months later.

<b>Cost commentary</b>
The unit construction cost of £574/m2 compares well with Spons’ updated estimate for exhibition halls (£550-£760/m2). A basic level of finishes suitable for agricultural shows combined with the exclusion of exhibition seating and floor finishes from the main hall has kept the figure near the bottom end of the range, despite extra costs to cope with abnormal site conditions that included soft sand and groundwater.

<b>Specification</b> <b>Structure</b>
The superstructure comprised a steel frame adopting a primary grid of 12 m aligned with a secondary grid of 6 m. The main cellular roof beams are at 6 m centres supported by columns at 6 m centres around the periphery. Along the line of the aisle columns, the roof beams are supported on columns at 12 m centres and trimming beams, which, in turn, carry the 6 m grid of beams supporting the roof system over the aisle section.
The steel structure of the foyer is also a combination of 6 m and 12 m grids supporting a butterfly roof whose pitch follows that of the existing hall. The foyer and café are thus clearly articulated from the exhibition hall that rises above them.
The power-floated concrete ground-floor slab contains 300 mm2 lateral services ducts running from east to west across the hall, which are linked to an underground services subway formed from precast concrete units.

<b>External facades</b>
The exhibition hall was clad in standard, large, semicircular profile steel sheets, polyester powder-coated and fixed horizontally with vertical division flashing at 6 m centres to suit the structural grid.
The ancillary accommodation was clad in aluminium composite panels and PPC aluminium-framed double-glazed curtain wall sections with clear glazing.
The toilet pods were clad in vertical profiled steel panels.

<b>Internal finishes</b>
Exhibition hall floor: power-floated.
Foyer and café floor: ceramic tile.
Offices: industrial-grade carpet tile.
Kitchen, first-aid and WC areas: vinyl sheet.
Walls generally: emulsion paint on blockwork or plasterboard.
Walls in hall: fairfaced block to 3 m, liner sheet above.
Ceilings: mineral-fibre tile inlay in suspended ceiling grid or polyester powder-coated roof lining sheet in foyer, café and hall.

<b>External works</b>
Vehicle yard: concrete block paviours.
Footpaths: tarmacadam.
Exhibition square: tarmacadam with concrete paving slabs underneath the building canopy.

<b>Heating and ventilation</b>
The hall is mechanically ventilated and heated from a boiler and air-handling unit located at mezzanine level over the toilets and kitchens that serve the café and foyer.
Controllable high-level louvres on each of the long sides of the hall provide natural ventilation. These louvres are also used for the evacuation of smoke should a fire occur in the exhibition hall.
The foyer and café are ventilated from an air-handling unit at mezzanine level. Heating to these and all ancillary areas is by low-pressure hot-water radiators.
The hall is mechanically ventilated and heated from an indirect gas-fired air-handling unit located in the plant room at mezzanine level above the toilets and kitchens, serving the café and foyer.
Controllable high-level louvres on each of the long sides of the hall provide natural ventilation. These louvres are also used for smoke evacuation should a fire occur in the exhibition hall.
The foyer and café are ventilated from an air-handling unit at mezzanine level. Heating to these and all ancillary areas is by low-pressure hot-water radiators. Kitchen ventilation is provided by air-handling plant located in the mezzanine plant room.

<b>Lighting</b>
400 W high bay luminaires are used in the hall to provide a uniform lighting level, with security lighting provided by fluorescent luminaires.
Decorative pendant luminaires provide lighting to the café and circulation areas with lighting suitable for VDU usage in the offices and organisers rooms.
IP65-rated fluorescent luminaires are provided in the services walkway and plant room, with “easy-clean” luminaires in the kitchen.
A comprehensive emergency lighting installation comprises fluorescent luminaires in the main hall with integral emergency fittings elsewhere and maintained emergency exit signs throughout.

<b>Services distribution</b>
A new substation, comprising switchgear and a 1000 kVA transformer, provides power to the hall.
Within the hall, the exhibition stands are individually serviced for power, data, telecoms, water and drainage by a 3 m grid of floor-level outlets, which are fed by an underground walk-through service tunnel and spur ducts.
All other areas are serviced more conventionally by a combination of surface and recessed power, data and telephone outlets.
Hot water is provided to the kitchen and café toilet area by a hot-water calorifier located in the mezzanine plant room. Hot water is supplied to the organiser’s rooms and toilet pods by local unvented water heaters.
A combined fire alarm and public address system has three speaker circuits, allowing flexible operation of the public address system. Microphones are provided in the organiser’s room with a fireman’s microphone at the main entrance.