The Weston, Yorkshire Sculpture Park

The Yorkshire Sculpture Park sits in the grounds of Bretton Hall, an 18th century country park estate. Since its opening in 1977 the Sculpture Park has developed a series of indoor exhibition spaces that complement the sculpture arranged across the landscape. The Weston is the latest addition, providing a visitor centre and gallery. At The Weston, the architect has fully embraced this aspiration. The building is truly of its landscape.

The new gallery and visitor centre is set into the hillside of a former quarry, a location that has informed and inspired its construction and appearance. It was conceived as “a sculptural element, emerging from the earth”, says Fergus Feilden of architect Feilden Fowles. ‘We wanted the building to read as being ‘of the land’ with texture and layers like geological strata.”Cement-stabilised, rammed earth was investigated as an option, but was discounted due to detailing constraints dictated by the material, which would have compromised the architectural design intent and reduced durability in comparison to concrete.

“Rammed earth needs to be protected to be durable,” explains project engineer Chris Stobbart at engineersHRW. “Walls using this technique are typically made with ‘good boots and a good hat’, with the rammed earth raised above the external ground on an upstand with well-drained footings and with generous overhanging eaves at the top to protect the walls.

Concrete was able to offer increased durability with less risk to the client and more flexibility to achieve the desired architectural finish.”Rather than physically ram the concrete in place, the walls were constructed using reinforced concrete poured in shallow layers. Within each 1.2m lift of formwork are four sub-layers, each containing a different concrete mix with varying pigments and aggregate.

The formwork was pre-treated with retardant so that, once struck, the face of the concrete could be jet-washed to expose the aggregate and provide the layers of rough texture required.engineersHRW specified structural parameters for the mix within typical limits for reinforced concrete. By testing and developing sample panels, the contractor determined that it could achieve the desired architectural appearance with a standard S3 consistence class.

This provided a mix that was well graded to give an even distribution of aggregates without segregation. The compressive strength of each mix was confirmed by cube testing. The sub-layers within a 1.2m lift were each poured before the sub-layer below was fully cured thereby allowing them to blend together to give a better shear interface. “Some small variation in stiffness between layers is expected due to the use of different aggregate types,” says Stobbart, “but since each layer is relatively long and consistent between vertical joints, local stiff points within a wall panel are avoided. Otherwise, they could lead to cracking.”

The jet-blasting was accommodated by increased cover to the reinforcement bars. This increased cover together with the wide spacing of the reinforcement, also enabled adequate compaction of the textured concrete when poured in such shallow layers. Concrete subcontractor Northfield Construction built four sample walls in its yard to test out different construction techniques, including tests for shot-blasting, types of retardant and curing times between pours.

Part of the north wall in the building was also used as a construction trial. Only after such careful consideration and testing was the final combination of mixes and finishing processes scheduled for construction. The project also includes structural concrete exposed internally with smooth, in-situ walls enclosing the gallery space. Its sawtooth roof is formed as a series of inclined reinforced concrete beams spanning 10.5m over the gallery.

The curved profiles draw north light into the space and across their timber-board marked surface. Each profile incorporates a slotted lighting track and cast-in fixing points for the gallery to suspend artworks. As well as the gallery space, the building includes a restaurant, shop and public foyer. The Weston, Yorkshire Sculpture Park has been shortlisted in the RIBA Stirling Prize 2019.

Featured in CQ Summer 2018 (pg 12)