Hitting the high notes

Shrewsbury Music School’s timber-panelled roof combines strength and acoustic sensibilities, writes Rob Gregory

Roofs have rarely been the generator of twentieth century architecture. Certainly, the modernism that grew from the lineage of the International Style produced a roofless generation of buildings. Roofs were either all or nothing. You either had a flat roof, where the architecture was principally derived from the form and expression of the elevations, or you have dramatic roof forms by Nervi and Saarinen and others, that gave their architecture an identity.

The synthesis of the two was rare. Distinctive roof forms that are part of an assembled composition where walls and roof were given a mutual expression were limited to the work architects such as Hans Scharoun, Hugo Haring, Michel de Klerk and Eric Mendelsohn. In their work the volumetric and material nature of roofs were composed carefully to give their buildings very particular identities. The new music school in Shrewsbury has arguably taken its inspiration from this line. Located on a split level site within the grounds of Shrewsbury School beside the River Severn, this new building will re-house the existing department, offering improved facilities for both teaching and public performances.

Citing Malting buildings and agricultural warehouses as their inspiration, and making reference to the formal similarity it bears to Mendelsohn’s Hat Factory (Luckenwalde 1923) Pringle Richards and Sharratt Architects have designed a building that synthesizes the principles of both the functionalist and expressionist traditions. The form, it is argued is a direct function of its internal organization, whilst the external expression is derived from a pragmatic yet highly controlled composition of materials.

Under the direction of John Pringle this should come of little surprise. As a leading influence in the work of Michael Hopkins and Partners with Ian Sharratt for almost twenty years prior to establishing PRS in 1996 (see Profile Building Design April12 2001), Pringle has worked on some of Britain’s most distinguished roof structures, testing the composition and elevation of roof forms. In the early Hopkins years the technical differences between wall and roof were questioned on buildings such as on the Patera Building System where wall became roof whilst, at Schlumberger the dramatic fabric roofs not only had technical and environmental benefits, but the expressive juxtaposition of elements resolved what Pringle described as "contradictory uses". Housing a drilling test station and cellular offices resulted in a building that is "curiously awkward in its form", yet beautifully resolved. The same composed awkwardness is evident at Glyndebourne where flytower, auditorium and backstage volumes skillfully become one.

At Shrewsbury, despite the shift in scale and budget, PRS have applied the same rationale in resolving conflicting functional and compositional issues. The organization of the building is so clear that it is difficult to imagine a more efficient solution being possible. A large triple height performance space at the heart of the building is wrapped in a double height elliptical ring of cellular accommodation - separated by a continuous inhabited corridor. The residual space between the facetted geometry of the auditorium and the elliptical geometry of the perimeter accommodation punctuates the corridor with waiting and storage spaces. The radial music practice rooms naturally produces spaces with splayed walls (essential to avoid standing sound waves being produced) avoiding the contrived awkwardness of having to resolve such angles within an orthogonal envelope.

Structurally, the masonry lower ground floor provides a massive undercroft to accommodate the loudest music rehearsal spaces and a mechanically assisted cooling labyrinth for fresh air intake, forming a base upon which sits the predominantly timber superstructure, comprising perimeter columns and beams and a dramatic faceted roof.

The auditorium’s faceted roof structure actually has no structure to speak of, rather it is formed like an igloo where solid spruce panels prop each other in compression. Described by Pringle as being like very thick sheets of plywood, the solid 110mm thick MERK-Dickholz panels were not only strong enough to eliminate the need for a traditional frame and infill structure, but also due to their inherent mass were more appropriate acoustically than PRS’s initial stressed skin approach.

Where possible the panels have been expressed as self-finished units such as in the perimeter music practice rooms as exposed soffits, however this was not possible in the auditorium as the panels could not be given the necessary curved form required by the acoustic engineer Richard Cowell. As a result curved plywood panels face the units where required.

PRS was introduced to the German product whilst collaborating with Thomas Herzog on a housing scheme in Berlin and following poor responses from UK specialist timber contractors, the decision to use MERK not only proved to be a very successful collaboration, but due to a weak Euro had cost benefits which made the system affordable.

It is unlikely, considering the modest scale and budget, that a prefabricated structure would have been envisaged - Merk however were able to use PRS’s own 3D model of the roof structure, perimeter roof beams and columns to manufacture the units, which once on site were erected in little over two weeks. Once erected, the insulation, membrane and Cedar Shingles were then fixed directly to the panel’s top surface. The result being that slender composite construction allows the external expression of the roof to be true to its internal form.

Originally detailed as a terne coated stainless steel roof, the roofing material was changed to shingle, to strengthen the material continuity of the scheme as essentially a timber building, and to ease the necessary resolution of the faceted and elliptical geometries that would have produced too many complicated seam details. Shingles, like fish scales provide a seamless skin to the roof, which is then crowned by a steel structure housing the required attenuators, ventilation dampers, and rooflights.

The day-lighting of the auditorium was very important to Pringle. He was keen to introduce a generous roof light in this scheme, offering the opportunity to walk into the auditorium from the landscaped gardens and appreciate the qualities of the summer daylight.

The tight budget of the scheme at £1025/sq m does not seem to have taken its toll on the quality of the building, which may be a virtue of its rational primary moves. It will be interesting however to see how the timber ages as there are four different species used as finished materials. Spruce for the structural panels, beams and columns, Western Red Cedar for the timber cladding and shingles, Larch windows and Birch Ply panels. Despite this Pringle believes the contrasts of the wood will give the building more life.

The building, which officially opened in February, has already proved to be a functional success. The natural cooling strategy coped with the hottest day of the year with a full audience, and the auditorium met the target reverberation time of 1.7 seconds without the need for any unsightly reflectors or absorbers.

Designed in a holistic manner, resolved in the round, the roof was the principle generator. Whilst the resultant form may be considered slightly ‘awkward’ with its dominant formal symmetry and its uneasy proportions, Pringle can explain everything in terms of the buildings function, and in the spirit of the functionalist tradition.

As the modernist commentator J.M. Richards wrote "whereas many symmetrical buildings are made so by forcing diverse elements into a formal pattern, this is a rare instance of a building in which divergence from symmetry would have been the first evidence of artifice." 

© Building Design 2001