Hitting The Timber High Notes
Barney Jordan, Structural Engineering Partner at multi-disciplinary engineering firm, Cundall, discusses the triumph of timber in musical education and how the award-winning King's College School, Wimbledon's state-of the-art new music school is an achievement of client vision, innovative architecture and structural design.
Key to the project's success has been the integrated approach between the architect, engineers, the school and the wider project team. Showcasing specially designed American white oak-lined ceilings in both the concert hall and rehearsal room, timber was the obvious choice of material in the design of the new music school.
The multi award-winning structure, which opened late last year, is part of the school's ongoing development masterplan and is the result of a clear vision by both the school and the architect, supported by superb engineering.
The Hopkins Architect's designed music school is arranged over three floors. The basement level comprises loud practice rooms for instruments such as percussion, drums and brass, while the ground floor is home to the stunning 200-seat concert hall which can accommodate a 70-piece orchestra, a new porters' lodge and staff administration space. The top floor consists of an orchestra rehearsal room, additional practice spaces and the porter's residence. Both the concert hall and the orchestra rehearsal room have specially designed American white oaklined ceilings, which create a wonderful acoustic and reveal the exposed triangulated structure of the building.
The project team, comprising the architect, engineer, fabricator and contractor, went through extensive deliberation before arriving at the choice of timber as the dominant structural material. During the concept design stage, concrete and steel were evaluated for the roof structures but they didn't meet the structural honesty that Hopkins aimed for in their vision for the buildings and would not have been as aesthetically pleasing.
In the end, timber was chosen for its good compression qualities, which suited the requirements of the triangulated roof design, its sustainability credentials and its ability to achieve the architect's aesthetic requirements to integrate the structure with both the interior and exterior finishes.
The shape of the main concert hall roof and the smaller orchestra rehearsal room roof – affectionately known by the design team as 'the baby roof' – are governed by the acoustic requirements of the spaces. The elegant glulam diagrid structures of these roofs not only result in a very efficient way to create the required geometry but also provide a support system for the integrated timber acoustic panels.
American white oak soffit lamella glulam beams were selected to match the American white oak veneer of the acoustic panels. The diamond structural grid matched both the interior acoustic panels and the external tile pattern, providing a cohesive and ultimately quite beautiful design, which contributes to the space functionality.
The main challenge Cundall faced was joining the timber diagrid members together, as the design required the six pieces of timber to come together at a single point. Both Cundall and Hopkins spoke to multiple timber fabricators to find an appropriate solution, eventually selecting a steel node to join each of the pieces together and designing each diagrid to withstand the different forces across the roof. This meant close collaboration with both the contractor and fabricator to ensure each piece was built to the correct requirements and assembled appropriately.
To keep the overall thickness of the roof to a minimum, some of the glulam elements are designed to be working close to their strength capacity, which made the connection details even more challenging. The roof design and the node connections are just one part of a very well-conceived and engineered project, but they exemplify the collaborative and detailed design process that was experienced by the whole project team.
The timber components were prefabricated offsite following close collaboration between the engineer, architect and timber contractor to ensure fine tolerances, low wastage and a cohesive and resilient design and installation. This meant less waste, as materials are not being cut down or amended on site. The timber selected was also PEFC and FSC-certified, meaning the construction material has a lower embodied carbon, compared to other standard materials and has been responsibly sourced from well-managed forests.
Close liaison was required with the timber contractor from tender through to construction, to make sure the components met the requirements and allowed for the triangulated timber diagrid design to have structural integrity and match the design details of the rest of the structure. Since the timber was prefabricated, the design could not be altered once construction had begun.
Timber is a natural insulator, and it provided a thermally efficient structure and building envelope for the music school. This meant lower running costs and increased resistance to the unregulated changes in air, water, heat, light and noise transfer from the outside environment. Using timber to satisfy the acoustic requirements in this way meant it could be integrated into the build-up of the envelope and resulted in an elegant and environmentally efficient design.
The entire design team worked hard to meet the vision of both King's College School and the architect, to ensure the design was fully co-ordinated ahead of fabrication. The process was collaborative through to final completion and has resulted in a beautiful and functional structure that will nurture a love of both music and building design for generations to come.