Effects of design configuration on decay initiation and progression in non-durable wood

Rod  Stirling; Grant Kirker

doi:10.22320/s0718221x/2026.01

Authors

Rod Stirling FPInnovations. Vancouver, BC, Canada. https://orcid.org/0000-0002-4356-563X
Grant Kirker USDA Forest Service. Forest Products Laboratory. Madison, WI, USA.

DOI:

https://doi.org/10.22320/s0718221x/2026.01

Keywords:

Aboveground exposure, field testing, moisture content, design configuration, service life, Tsuga heterophylla, western hemlock, wood decay

Abstract

Wood used above ground and exposed to moisture may be vulnerable to decay. The initiation and rate of decay are influenced by several factors, including substrate type, moisture and temperature. The design and geometry of wood components affect moisture dynamics and may therefore influence both the initiation and progression of decay. This study evaluated the impact of nine different design configurations on the durability of wood components in a field experiment conducted at three North America sites with distinct climates. The tested variables included specimen volume, the presence of impermeable surface coatings, and the arrangement of appressed boards. Significant effects on both decay initiation and severity were observed, with water-trapping features such as appressed boards and sealed surfaces associated with earlier onset and more extensive decay over a fixed period. The results suggest that longer service life may be achieved by avoiding design features that retain moisture or inhibit drying.

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Author Biographies

Rod Stirling, FPInnovations. Vancouver, BC, Canada.

Biography

Grant Kirker, USDA Forest Service. Forest Products Laboratory. Madison, WI, USA.

Biography

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