Wood, Wedges, Joints, and Jigs: CNC Milling a Pavilion with Low Grade Timber

Pavilion Approach
Pavilion at Summerhill Farm in Papamoa, 2022

This thesis aims to develop a methodology for the Computer Numerically Controlled (CNC) fabrication of a timber structure using relatively low grade, unstable timber. It investigates both how to design a structure that can deal with the use of unstable timber and the processes required to use CNC milling techniques on unstable timber. The thesis aims to build on the learnings of previous theses from the School in this field of research, developing the processes required for the fabrication of traditional timber joinery using CNC milling. In doing so, the use of CNC milling to create timber joinery can be better utilised in becoming a more widely applicable fabrication method, such as in situations where material options are limited. As part of this thesis, an application of this fabrication method has been tested at Summerhill Farm in Papamoa through the construction of a small timber pavilion.

CNC milling is a highly precise fabrication technology, and as such it normally requires a highly precise and stable material to work with. The problem faced by previous students and I is that we were supplied with timber that was neither precise nor stable. Therefore, my question became: how do you apply the highly precise CNC milling fabrication technology to an inaccurate and unstable material?

CNC Post Batch Larger
CNC machining of posts
J2 Wedge Prototype
Wedge joint prototype

My response to this problem was to use a wedged joint – a traditional ‘low tech’ solution. Each joint uses a clearance-fit connection combined with wedges to allow for lateral movement or adjustability to cope with warped, bowed or twisted lengths of timber. The wedges allow the joints to be tightened to create strong moment connections and also allow the joint to be tightened or adjusted as the timber moves over time.

Interior Pavilion
Detail Shot Pavilion
Detail showing wedge joints

The final outcome of the thesis is a worked example of the material, methodology and fabrication learnings gained throughout the year. The pavilion at Summerhill Farm is the final in a series of investigative models exploring how CNC milling can be used to fabricate a timber structure with unstable timber, as well as the next step in developing a methodology for the CNC fabrication of timber joinery.

Interior Truss View