Dowel-Laminated Puncheons: A High-Performance, Low-Waste Mass Timber Assembly

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.

https://doi.org/10.35483/ACSA.AIA.InterMaterialEco.23.23

Volume Editors
Caryn Brause & Chris Flint Chatto