Alfriston School is a state-funded girls school with Academy status catering for secondary-age day and boarding for a wide range of special educational needs and disabilities between the ages of 11 and 18.
The school has day places for up to 120 pupils, and provides residential care for 20 of those pupils. Most pupils have moderate learning difficulties, and a large majority have additional needs, such as speech, language and communication difficulties, sensory impairment, or physical difficulty. The school serves the whole county of Buckinghamshire and a number of neighbouring local authorities. It became a Specialist Sports College in September 2009 with science as a second speciality subject.
Duggan Morris Architects was commissioned in January 2008 following an invited tender and interview process to replace an existing redundant swimming pool structure with a new up to date facility. At the time of the commission the current sports department consisted of a derelict swimming pool, gymnasium and changing area. The vision developed in conjunction with the school steering committee evolved to improve the provision entirely and potentially open the swimming pool to the public. A number of funding streams were targeted including private fund-raising, Sport England and Local Government. A masterplan was prepared by Duggan Morris Architects to suit a phased programme of release of finances consisting of a new pool structure, refurbished gymnasium, new enlarged changing facilities, staff offices and a fitness suite.
The entire project was split over 2 phases with a small extension to the gym completed in 2010 followed by the main pool extension thereafter commenced in 2013 – the subject of this document. Planning permission was obtained in November 2009. The project was completed in June 2014 following a 50 week construction programme.
The scheme consolidates the existing and new sports facilities into a fully integrated sports department defined by one singlular block containing gym, changing facilities, fitness suite, admin offices and swimming pool. A new changing facility is connected onto the side of the existing gym with the pool extending into the landscape beyond.
The site levels have been altered to bring the primary entrance to the sports department central to the pool and gym with a secondary entrance to the rear of the gym permitting a public and private entrance to suit out of hours use. The new arrangement caters for 24 pupils within the pool at any one time and a further 24 in the gym building.
Wide access ways and large storage areas are included to service varying disabilities and hoist equipment. The overall permissable build footprint within the defined area was compressed by the greenbelt to the south skirting around the playing fields and the protected trees to the north.
The new pool building, sits discreetly at the rear of the site, facing directly onto the greenbelt land. Intended to be a contemporary expression of the local pitched roof vernacular, but executed with subtlety, the design of the new pool enclosure envisages a raised timber structure, articulated by three repeated folded roof segments.
The roof creates a dramatic internal landscape viewed from within the pool and also serves as an acoustic baffle thus preventing a high reverberation of sound, which is a crucial aspect of the brief.
A 1m narrow glass strip around the edge of the building, separates the pool roof from the rest of the base reinforcing the apparent floating form. Thus the privacy of pool users is protected and the panoramic view preserved.
Due to the very steep level changes from east-west and north-south, a heavy concrete retaining base structure was necessary. The substructure and pool container is constructed using on site traditional assembly methods consisting of concrete strip footings and retaining walls, a poured concrete pool container, and displacement tank. The pool is designed as a level deck pool ie. the water is level with the adjacent floor, with a simple flush drainage floor perimeter channel and beech tile.
The prefabricated roof was manufactured off site (by Cowley Timber) in 12 triangulated truss modules, the largest being 15 long x 5.2 high meters. The trusses were delivered with a weather tight membrane ready for roof dressing. The interior face is factory finished. The entire assembly took place over a
4 week period. This method offered precise, high quality finishing with no requirement for temporary internal or external scaffolding as well as cost and programme benefits. A standing seam roof system with integrated cladding clips supports the roof timber allowing the entire pool roof to be clad in the same material, with precise spacing and alignment.
All rainwater pipes are external but hidden behind the timber rainscreen. The pool roof is raised off the concrete deck with slim circular posts located at each cranked position. The glazed strip is achieved using a self-draining shuffle glazing system with minimal framing components. The cranked cills follow the geometry of the facades above and are powder coated matt black.
The existing building is cleaned up and using colour a simple reading of the volume is intended, so white windows and contrasting colours are eliminated. The facades are (re)rendered in black along with the base of the pool support structure to provide stark contrast to the Plato cladding.
The interior finishes palette is minimal with the majority of materials self-finished. The changing room timber structure is exposed and walls are constructed of fair faced concrete blocks. Tiling is used in the wet areas only and a black sheet UPVC flooring is used throughout. Lighting is achieved using LED strips following the exposed lines of structure both in the changing and pool area.
The project challenge was to provide a clear spanning structural solution that allowed maximum off-site pre-fabrication without the aesthetic compromise of appearing that it had been simply bolted together.
The ideal solution was to pre-fabricate 12no roof, 12no wall and 2no gable stressed skin panels constructed with primary glulam framing members and secondary glulam infill members working compositely with a cross laminated timber skin
as an efficient engineered solution that could be achieved under factory controlled conditions.
An intensive design process was undertaken to achieve the complex geometric planes and iterative structural analysis.
The many planes of the structure surface were defined by the architectural intent which provided an inherently stiff and stable structure when
fully assembled but manifested in challenges of assembly, distribution, transportation and site handling due to the proportions of the roof panel sizes being a triangulated shape of circa 15m long x 5.2m wide and weighing 1.7 ton.
A major ambition was to conceal all traces of the galvanised metalwork and bolting which was not only necessary to connect the off-site assembled primary glulam frame of the individual panels but also to connect the interfacing panels as they were assembled to each other on site. The sequence of build was an important consideration as was limited tolerance. Trial assemblies were a luxury that space could not afford and so we were reliant on the accuracy of our 3D modelling and the CNC 5 axis router machine.
Reducing the amount of time required to attend
to the fully installed panels was another important CDM consideration and so close liaison with
M & E service engineers to provide concealed but accessible service routes was vital as was pre-finishing the timber surfaces with a 3 part coating system before the panels arrived on site to provide both temporary and permanent protection. Mock-up sections were manufactured to assist in this process. The end result is an efficient, elegant and functional example of an off-site prefabricated, highly engineered stressed skin panel solution to create an open space.