Description:

The role of the carpenter in traditional Japanese architecture was as much an architect as a craftsman. Buildings created by miyadaiku carpenters (carpentry techniques using interlocking wood without nails) involved sophisticated timber-to-timber joints that dis not rely on mechanical fastenings—nails, bolts, screws, and so on. This approach to timber architecture has been largely lost with the adoption of mechanical fastenings, especially in the construction of structures with many small timber members. In essence, this resulted from the high labour costs associated with making precision timber work, leaving this craft as largely the reserve of high-end furniture; in New Zealand, at least, such precision work has become largely absent from smaller building structures.

Sophisticated timber joints, however, are still used in structures with large timber members, each element of which costs many thousands of dollars. With such large-scale elements, the cost of accurate digital (CNC) fabrication is small relative to the cost of the members themselves. However, a gap in the application of this technology exists regarding small timber members, where the cost of the members is just a fraction of that of larger elements. The costs of CNC fabrication cannot therefore be justified, and screws are used.

The question that drove this project relates to these small members—how can simple three-axis CNC milling be used to fabricate sophisticate timber joints, creating viable timber-to-timber connections on small elements?

This project forms part of an ongoing series of projects carried out by staff and students [at a NZ university]. In the course of these projects, methodologies have been developed involving jigs to hold and consistently cut many small pieces of timber by locating sticks on the CNC milling bed. This massively reduces the set-up time associated with milling each element. Earlier projects successfully milled one face of the timber to create partial lap and cogged lap joints. However, there is a limit to the types of joints that can be fabricated when only one face is cut. For this project, a new jig methodology was devised to cut any face of the timber so that more sophisticated and complex joints could be fabricated. The client gave a further constraint for the project—that it be constructed from the client’s own Summerhill Timber, which was grown in the exotic forest that covers the project site. The most suitable species available was cypress, chosen for its durability, relative strength, and availability in relatively clear lengths (knotty timber is unsuitable when structural elements are slender).

The result is a forest classroom for use by visiting groups of school children, constructed from a lattice of small timber members connected by kashigi-orie (a form of mortise and tenon) joint. This learning space was, uniquely, created from trees in the forest where in now stands. Serving as a built example of how the technology can be applied, it dispels the notion that structures of this scale and budget must rely on unsophisticated construction methods.