Gridshell structures are light and efficient but their structural form is undeniably complex.
The unique attributes of a timber gridshell mean that even this double-curved structure can be built with a minimal use of materials, giving very efficient coverage of space. Unlike gridshells made of steel or concrete, which require many different complex curved shapes, the repetition of structural elements means a timber gridshell can be made from a set of straight, prefabricated, identical components.
As such, this gridshell uses 80 x 50mm sections of larch timber in a regular 1m grid. Ideally, a gridshell would be supported firmly all around its perimeter, but to allow for a more dramatic building with wide openings on to the garden, the Savill Building's gridshell has to be contained within a steel ring-tube, supported at several discrete points. This perimeter ring contains the internal forces of the structure and provides points of contact for the supporting quadruped legs, also made of steel. As a result of this design, load concentrations on the Savill structure had to be considered carefully.
Initially, the concept included steel cables to triangulate and brace the shell in its plane. But, to save cost and make a more elegant structure, cables were omitted. So, the plywood covering, which is needed to support the external raisedseam roof, provides the strength and stiffness needed in the plane of the shell. In supporting roof loads, this in-plane structure is just as important as the more visible laths. The structure's own weight is easily carried by the timber and, with no other loads applied, the stresses in the laths and the plywood bracing are very small. More severe loading conditions, such as wind and snow, had to be considered, with the structural plywood helping to transfer the extra forces through the domes or valleys of the roof, to the steelwork and the foundations.