Author(s): Emanuel Jannasch, Mark Mackinnon, Myranda Reay, Brendan Roworth & Ben Goldsmith
Converting a log to rectilinear timber adds constructional convenience, but also incurs material waste and consequent loss of structural capacity. Puncheons were a pre-industrial timber product: a log flattened on three faces and left “live” on the fourth. They were typically employed in log structures in a one-way mass-timber floor slab, not unlike dowel laminated timber (DLT). In 2022 an instructor at Dalhousie University (Jannasch), his co-authoring grad students, and ten teammates compared the values gained and lost in puncheons vs. conventional timbers, both in the production process and in their application as spanning members. A literature review by MacKinnon found historical and more recent work on round wood, but scant mention of puncheons. A purely geometric assessment of kerfs and slabs compared sawmill wastes and performance of laminated lumber and puncheon slabs. Goldsmith’s M.Arch thesis on forest-informed design points out that irrespective of structural performance, the additional mass conserved in puncheons sequesters carbon. Nonetheless, we built a specially designed apparatus to begin assessing actual loss of stiffness entailed in progressive sawing: load testing was carried out by Reay and Roworth. We also built a puncheon bridge and other structures to explore the tectonic and expressive potential of this construction. Positive results in most areas of investigation suggest further work be undertaken.
Volume Editors
Caryn Brause & Chris Flint Chatto