Zen gardens, wave pools and bowling alleys - in an English forest? All in a day’s work for Holder Mathias at Center Parc Woburn, finds Felix Mara
Leisure buildings are hard work for their architects: hotels require intensive MEP services and recreation facilities have complex operational needs. But the brief for Center Parcs Woburn Forest holiday resort in Bedfordshire, offering more than 100 leisure activities to the 350,000 guests it expects in its first year after opening last month, involved levels of technical complexity and sophistication that were, for its architect Holder Mathias, unprecedented, notwithstanding its experience of this type of project.
Working alongside an army of consultants, Holder Mathias was responsible for designing three complexes: the Village Square, which includes the 5,200m² Subtropical Swimming Paradise; the 24,500m² Plaza structure; and the smaller Waterfront family retreat. The project’s complexity was compounded by the design team’s strategy to integrate with and conserve its setting in 362 acres of forest, and avoid giving the impression that the site has been overdeveloped by regulating building heights and using convex plan geometries, which restrict the visibility of their facades.
The Subtropical Swimming Paradise, defining the south edge of the meandering Village Square, takes advantage of a change of level on the site and turns its face in the opposite direction, where more height was available for the sweep of its bowed glass elevation. This scoops daylight into the voluminous multiple-facility interior. Learning from the operational consequences of its Center Parcs Whinfell Forest which, as was the vogue in the 1990s, has extensive roof glazing, Holder Mathias limited light pollution and solar gain by combining insulating enclosures of standing-seam aluminium cladding and triple-layer ETFE cushions.
The external envelope comprises a shallow barrel vault co-joined with a half-dome, which is partially supported by diagonal struts at its highest levels. The half-dome and barrel then morph into a D-form with a curved vertical section which encloses the sides of the building. ‘When domes come down to the ground they feel quite claustrophobic,’ says Holder Mathias senior partner Peter Gamble.
The structure is a hybrid. Sculptural concrete pylons support glulam beams whose curved profile peels away from the perimeter soffits, allowing ventilation to sweep away their condensation. The third structural material is galvanised and painted steel, which raises the soffits above the beams, and is also used to form glulam splices and bowstring trusses supporting the curtain wall and the bay at the south end of the building. Stainless steel was considered unsuitable for the pool climate. The visual concrete finish to the pylons relies on stainless steel formwork and the GGBS substitute aggregate gives them a light tone. Unusually, the glulam beams themselves, each of which was transported to site in three sections, have a white semi-transparent stain for enhanced reflectivity.
The pool area floors are surfaced with stone, which provides good slip resistance, chalking up wet pendulum test readings of 36 plus. The client favoured a green quartzite aggregate render finish to the pool itself, rather than faience, and this also has good slip resistance. As this is a pool interior, the roof build-up and its vapour control required careful attention. Center Parcs’ sustainability strategy rests on factors such as its CHP system and material selection: like most of the resort’s facilities, the pool complex is mechanically ventilated, using pervious flexible ducts, and it was considered unnecessary to provide enhanced solar control to the glass facade. ‘We wanted plenty of heat, even on the hottest days,’ says associate director David Gallimore.
Programmatically, the Plaza is Center Parcs’ most complex building. ‘This complexity involved getting such vast facilities on to the site without producing a building which felt oppressive,’ says associate director Emma Jackson. Holder Mathias somehow packed a sports hall, a 7,700m² spa, a 75-bedroom hotel, a supermarket and conference facilities into the Plaza’s low-lying, stepped green roofed, insulating rendered envelope. Layer upon layer of inboard spa accommodation is divided into separate wet ‘experience’ areas and dry zones with support facilities, and a central drum funnels light into the heart of the complex.
By all accounts, architect, client, main contractor, QS and project manager worked in harmony, building on previous Center Parcs experience, and VE was comprehensive but constructive. Where requirements for service penetration allowed, post-tensioned slabs were substituted for troughs and cement-sand screeds, and a 50mm vertical movement joint running through the Plaza complex also allowed steel, concrete and hybrid structural frames to be separated, enabling the main contractor to keep its options open longer. The cut-and-fill strategy, developed in detail by the structural engineer, was critical to the concept of integrating the architecture into the site and minimising waste. Holder Mathias helped to reduce costs by explaining the quality of the concrete surfaces was so good that decoration would not be necessary. Many of these conceal retained earth held in place by Tensar reinforcement, which is doing the actual structural work.