National Opera House, Oslo, Norway

Recently completed in the harbour area of Bjorvika, Oslo, the National Opera House (Nytt Operahus) is a NKr3.3bn new opera house. Statsbygg, the Norwegian Directorate of Public Construction and Property oversaw the project which has been billed as the biggest boost for culture in Norway since the medieval Nidaros Cathedral was built in Trondheim. With a total cost of £420m, its design won an international competition and was opened by King Harold of Norway in April 2008.

The opera house is the first element in the planned transformation of this area of the city. In 2010 the heavy traffic besides the building will be moved into a tunnel under the fjord. Due to its size and aesthetics, the opera house stands apart from other buildings in the area. The marble-clad roofscape forms a large public space in the landscape of the city and the fjord.

DESIGN AND ARCHITECTURE

The opera house is split in two by a corridor running north-south, the 'opera street'. To the west of this line are located all the public areas and stage areas. The eastern part of the building houses the production areas comprising three to four storeys above ground. There is also a basement level – U1 – below this part of the building. The sub-stage area is a further three storeys deep.

The opera house has approximately 1,000 rooms and is the workplace for over 600 people divided into more than 50 groups. The building is composed of three main elements: front of house, back of house and the roofscape.

The 'roofscape' describes the building's sloping roof surface, which rises directly from beneath the fjord. It is designed with fractures, stairs, the stage roof surfaces and the stage towers as defining features to the vast platform from the sea to the uppermost levels – all of which will be accessible to the public.

The unusual sloping roof is very different from the surrounding buildings. The roofscape will be clad in white stone, and its details will provide a holistic and symbolic character to the building while also providing a variety of experiences as one moves past it.

The front of house incorporates all the public areas, located in the building's western section, with access from the nearby central train station. These public areas include the main foyer, a large performance auditorium with 1,350 seats and a small auditorium with 400 seats.

The large auditorium employs a classical form with a horseshoe-type plan and a high ceiling height, providing high-quality natural acoustics and good sight lines to the stage. In addition to the main stage there is also an under-stage complete with elevator, side stages, back stages and a back-side stage that can be used as a choir or orchestra rehearsal room.

The small auditorium has considerable flexibility in both stage and seating arrangements. The foyer is a grand, open room with a variety of lighting conditions and views of the surrounding city and fjord. The space is characterised by its simple use of materials and minimal details. A tall undulating wall defines the separation between foyer and auditoriums.

The foyer also contains rest areas, a coatroom, café, bars and a restaurant.

The production areas of the building are those termed 'back of house'. Here are all the workshops, storage areas, rehearsal rooms, changing rooms, offices, and every facility necessary to produce an opera or ballet. This part of the building has four floors and one basement. The architecture and the use of materials are functionally appropriate, with the exterior façade being composed of metal panels.

SHIP BARRIER

A considerable portion of the new opera house is positioned in or under the sea. There are two ferry terminals close by – the Revier Quay, which houses docking for cruise ships, is only 100m from the opera house.

A risk analysis in relation to ship traffic was carried out during the planning stage by the Norwegian Veritas organisation. They concluded that there was an 'unacceptably high' risk of a ship colliding with the new building. To solve this, a new underwater ship barrier close to the building was constructed.

The barrier is located just south of the opera house and sits up to 2m below the sea surface. It is 70m wide at its base and 10m wide at its top. The development of this structure was executed in cooperation with the Public Roads Administration and the Oslo Port Authority.

FOUNDATIONS

As the opera house is situated both on land and on water, there are considerable consequences relating to the foundation design, handling of polluted soil, control of moisture and the building's water tightness.

To create a stable and dry working environment, the construction required 12,000m² of steel sheet piling around the perimeter of the site. The foundations needed 28,000m of piles to act as supporting elements for the building above. The piles vary in length and can reach up to 55m below the water surface before meeting stable bedrock.

ACOUSTICS

The main auditorium has been designed so that no amplification or electronic assistance will be required to obtain the optimum acoustics. The room shape is designed to ensure that sound will naturally reflect around its surfaces to the audience.

The horseshoe form provides the best compromise between acoustics and intimacy and has been chosen for the new opera house's main auditorium.

The materials are also important with respect to reverberation and acoustics. With reflective walls and ceilings, the acoustics will be sharper, while broken surfaces create a more diffuse sound. The new opera house is designed to provide reflected sound early, combined with a long reverberation time. To provide the best possible solutions, both a physical model and a data model were used to simulate the room's acoustic qualities.

OPERA HOUSE LOCATION

The National Opera House is located in an area of the capital characterised by heavy traffic (both road and rail) and busy port activity. In addition to the opera house, Oslo council is developing the area into an attractive centre for business, dwelling and cultural activities. This will involve placing the nearby E18 highway into a tunnel under the region.

KEY CONTRACTORS

In June 2000, the Norwegian architect firm Snøhetta AS unanimously won the contract to design the new National Opera House, beating competition from 230 other entries. The key structural engineers are Reinertsen Engineering AS, Ingenior Per Rasmussen AS and Erichsen & Horgen AS. Norges Geortekniske Institut (NGI) is the geotechnical consultant.

Other contracts were awarded to: Theatre Projects Consultants, London, UK (theatre consultant); Scandiaconsult AB (foundations and building contractor); Brekke Strand Arup (acoustics); Johns J Syltern AS and Veidekke Entreprnor AS (site preparation, phase I and II, respectively); Skandinaviska Glassystem AB (glazing) and Bosch Rexroth AS (hydraulics / pneumatics).