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Dimensional Changes in Structural Glued Laminated Timber

Technical Note

Glulam is manufactured from dried lumber which minimizes dimensional changes from moisture compared to sawn lumber. However, members can shrink or swell as they acclimate to their in-service environment or are exposed to the elements during transit and storage.

This publication is designed for: designers, builders, and inspectors

This publication explains how to estimate dimensional changes in width and depth, with dimensional change coefficients by species and equilibrium moisture content by temperature and humidity. It includes two example calculations. The publication also clarifies why moisture-related changes may exceed manufacturing tolerances without indicating noncompliance with ANSI A190.1.

Key sections include:

  • Introduction and overview of dimensional changes in glulam

  • Dimensional tolerances at the time of manufacture

  • Shrinkage and swelling characteristics of wood

  • Example calculations illustrating dimensional changes in glulam

  • Summary and references

Published by APA — The Engineered Wood Association.

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