Timber for the roof structure was European larch, sourced from FSC plantations in Windsor Forest on The Crown Estate. This was specified as being the best timber from a local source to meet the strength requirements after rigorous grading.
The design then allowed the re-use of lower grade timber in less critical areas, demonstrating the potential of home-grown timber for structural purposes. A total of 105 prime quality trees were carefully selected and felled in accordance with the ongoing FSC forestry management plan.
English oak was used for the internal hardwood flooring. A natural matt oiled finish was chosen to accentuate the timber grain and durability. Oak was also used for the rainscreen cladding to the gridshell roof, supported on an adapted metal support clip and timber bearer system fixed to the metal standing seam roof.
The gridshell roof consists of four layers of timber, which are laid out flat and manipulated into a doubly curved shell form. The curved shell is braced in plane, for shear strength and stiffness, by the Birch plywood sheathing that supports the roof insulation and outer cladding. For practical site joining, the Larch laths are connected directly to the steel edge with fingers of Kerto LVL, which are bolted between the laths and support ledges on the tube.
The Savill Building roof is four times the size of the Downland Gridshell and so its construction moves the technique forward and has enabled further development of understanding of the structural design and methods of construction for such structures utilising a programme of testing at Bath University.
The magic of the building is exposed very slowly. Visitors first see the curves of the roof, before entering through a deep earth bund. The openness of the building is then revealed, the roof apparently floating above the floor-to-ceiling glass panels which lead out to the garden itself.
Inside, the lattice of the gridshell is exposed to visitors standing 9m below. Outside, the overhanging roof projects a wide terrace from sun and rain to provide a year-round extension to the building overlooking the garden as it drops away. From here, an avenue of upright oaks aligns with those in the car park and leads down to a viewing platform where visitors can enjoy a panorama of the garden.
The judges were unanimous in their praise for the approach of the building to the site and as a successful piece of architecture in the landscape.
‘Internally the effect is one of light and space, a very pleasant place to be,’ they said ‘ it was evident that great care had been taken to ensure that even small details were just right. We were not able to find a service box cover that was not aligned with the edges of the floor boards and that did not have the infill made from the same board as the one on the outside of the box.’
LocationWindsor Great Park
ArchitectGlenn Howells Architects
Structural EngineerBuro Happold and HRW
Wood SupplierThe Crown Estate, Windsor Great Park
SpeciesEuropean larch and English Oak, Windsor Forest; Spruce LVL and Birch plywood, Scandinavia
ClientThe Crown Estate, Windsor Great Park
JoineryThe Green Oak Carpentry Company