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Moisture-Related Dimensional Stability

Technical Topic

Wood structural panels like plywood and oriented strand board (OSB) are hygroscopic materials that respond to changes in environmental moisture conditions.

Whether exposed to humidity variations during service or direct wetting during construction, understanding moisture-related expansion and swelling is essential for preventing common issues like panel buckling and ensuring long-term structural performance.

This publication is designed for: builders, contractors, engineers

The publication provides comprehensive technical data on equilibrium moisture content, linear expansion coefficients, and thickness swell characteristics for both plywood and OSB under various exposure conditions. It includes empirical formulas, comparative data tables, and graphical representations that enable practitioners to predict dimensional changes and incorporate appropriate design considerations. The publication also references standardized testing methods and relates findings to practical construction applications.

Key sections include:

  • Equilibrium moisture content of solid wood and wood structural panels

  • Dimensional stability: linear expansion and thickness swell

  • Moisture response during wetting cycles

  • Predictive formulas and data tables

Published by APA — The Engineered Wood Association.

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