David Noble of architect White Design says: 'The brief requires the building to function both as an operational office and visitors'centre for the public and construction professionals. The split-level section allows the office to function independently and privately while still exploiting synergy with the display area.
'The chosen design results in a building made up of two complementary roof forms constructed from a gluelaminated timber framework.The two roofs are different in character: the south facing roof - an elegant concave sweep of natural slate tiles - is visible from all approaches; the convex north roof is clad in cedar shingles and acts as the primary means for daylight to enter the building through a second array of Velux windows and through the clerestory windows that join the two roofs together.
'The two roofs shear relative to each other along the eastwest axis, providing a natural entry point at the east end of the building and an exit point to the terraced garden at the west end.The axis of the building is curved to respond to the site topography and present a welcoming entry to the site.'
Julian Sheppard, structural engineer for Buro Happold writes: 'The building's structure includes a timber glue-laminated frame supported off a concrete base and first floor.The timber structure defines the building's external walls and its roof.From this frame the internal first floor is supported.The 800 x 200 gluelaminated beams span a 15.5m width and up to the apex at a 12m height.The timber frame repeats on a 6m grid - however, this grid rotates by 4o or 9o.This change in grid set-out ensures that the building is curved in section and on plan.
The building's transverse stability comes from the inherent triangulated form of the timber structure.However, the stability elements in the building's longitudinal direction had to be placed within the curved roof fabric because the architect requested no internal bracing.
'The client was also keen to see as many windows as possible, so bracing was restricted to one bay only.Further to these constraints, the architect requested that a 75mm shadow gap be incorporated between the internally exposed timber structure and the internal face of plasterboard skin (hence, from inside, the roof would appear to float above the timber structure).
'This, in effect, dislocated the stability of bracing members within the roof from the vertical support members.As a result, a complex steel connection was designed in weekly co-ordination meetings held between the design team and the steel and timber contractors.This connection can be seen (without bracing elements) on the attached photos.
'The connection incorporates changes in angles both vertically and horizontally and ensures that all stability forces are catered for. It also fits within the roof fabric, ensuring easy plasterboard installation (adopting countersunk bolts) and reduced interference with roof joist elements.Every nodal connection is an individual design.The final design of this constrained and difficult part of the building was an achievement of co-ordinated discussions between all parties.'