16 CITY OF LONDON FREEMEN’S SCHOOL POOL, ASHTEAD, SURREY A box of two triangles
The pool has an interesting geometry with slightly uneven elevations and a roof comprised of two triangular zinc sections. It resembles a rectangular box which has been slightly squashed at two corners and folded along its top. The ridge junction between the two triangles runs diagonally across the space, creating an offset, dynamic rhythm externally and internally, expressed in the CLT ‘ribs’ that hold up the structure.
We have been truly impressed by the swift construction of the pool, and how it fits in the woodland space and complements the school
as a whole Roland Martin, headmaster, Freemen’s School
Adam explains how the building’s form was developed during the design process: “We began with the end requirements of the buildings. Then, we took a rectangle and extruded it, and you’ve got quite a conventional box, we then simply pushed down two adjacent corners of that box, and picked up the remaining two corners.” A standing seam zinc cladding in a dark copper colour was chosen to cover the building’s unconventional exterior, with seams forming vertical ribs which are intended to help the structure blend into the landscape. Another reason standing seam cladding was used is because it is a more traditional material, responding to key features of the school’s main house.
Off-site timber
Led by contractor Gilbert-Ash, the construction of the pool is centred around a glulam portal frame braced with CLT panels. The use of engineered timber provides a fast, efficient, carbon neutral method of construction that provides both structure and internal finish.
PROJECT FACTFILE
Architect: Hawkins\Brown Structural engineer: Eckersley O’Callaghan Services: Skelly and Couch Contractor: Gilbert-Ash Landscape designer: BD Landscape Transport engineer: Motion Ecology advisor: Aspect Arboriculturalist: TreeLine BREEAM assessor: SRL Project management: Pick Everard
The all-timber construction also has a number of advantages in dealing with the challenges of a pool environment – it is resilient, a thermal insulator and corrosion resistant. On site, the erection of the glulam portal frame and cross-laminated timber walls and roof took just over three weeks. This allowed the detailed design and full construction of the building to be delivered in one year.
The natural internal surface of the structural timber roof and walls is left exposed, and has been stained white. Here, the material acts as a complemen- tary feature to the external setting and helps to create a special environment to swim in.
This is enhanced by the structurally expressive roof geometry with its series of shifting glulam frames, the result being a visually dynamic space. Cossey comments: “The design allows students and spectators to really
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understand how the building has been put together. Even if they’re just visiting, they can really understand the structure.” He adds: Structurally, it is a very honest building.”
A softwood spruce is used throughout – in the CLT panels and glulam beams – which, as Cossey says, “ties in nicely with the surrounding woodland.” The elements were formed offsite, with all panels, beams and columns prefabricated by Wiehag in Austria, then assembled on site. The whole superstructure was erected in just under two weeks.
Cossey says CLT is being used increasingly on a wide range of projects: “People are starting to see the potential of CLT. A little over a decade ago it was a method of construction that was widely disregarded in the UK, whereas today contractors are increasingly suggesting this as the principal method of construction.” BIM software helped optimise the process. “Using BIM technology we can generate 3D models with relative ease,” says Cossey. “This allows us to create a very complex geometry, which can be imaged on a computer, then sent straight to factory to be manufactured.”
Collaboration Cossey notes the “fantastically collaborative” experience between the client, design team and contractor. He continues: “Where there were challenges, they were dealt with swiftly. From day one, there was a very positive, can-do mentality. It was an absolute pleasure to work with everyone involved.” Roland Martin, headmaster of the
school, gave a glowing testimonial on the finished building: “We are overwhelmed by the beauty and quality of the new swimming pool – it is a fantastic new asset for the school and the local community. “We were impressed by the swift construction of the pool, and how it fits in the woodland space and complements the school as a whole.”
It is not often that fires are a blessing in disguise, but it appears to be the case here, with the school now having a striking architectural asset for its students. Relocated to its proper location as one of the school’s sports facilities, and taking advantage of, as well as enhancing, its woodland location, it’s not hard to see why it has picked up RIBA South East and national awards. Lucky students and visitors will be able to ‘swim among the trees’ for decades to come.
ADF AUGUST 2018
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