Simple vaulted roof forms allow a dual expression of engineering and architecture to be realised. The elevation afforded by giving a depth to the roof allows the Engineer to take advantage of the effects of gravity on structures.
An early example of this is the concrete domed roofs designed to act in compression. Vaulted forms need to be buttressed around the perimeter to prevent a spread of the dome. Alternately a tie can be provided around the perimeter to similarly prevent spread. Early dome structures can be seen to have wrought iron ties performing this function.
Bringing forward these ideas it is far easier to design such a structure in this age.
The short span of the extension allows simple affordable timber elements to be used to form the roof structure. Timber is naturally effective in compression and the jointing of these elements is relatively straightforward. The perimeter tie was also formed in timber with steel connecting elements used at corner junction locations.
Detailing of the respective junctions required an understanding of the forces acting, be it tension or compression. Compression joints are far easier to consider as the direction of the force is inclined to keep the junction together. Tensile forces require more emphasis to be placed on the connectors that need to transfer forces between members. Stress reversal from wind uplift also had to be considered to make sure that the roof could resist this also.
By consideration of the above, it was possible to detail junctions that are simple and neat and give a clean canvas to express both the architectural engineering.
Project Architect: Joe Howland
Photographs: Joe Howland