Wood science · Version 1 · Published September 18, 2026 · AI-assisted educational synthesis; not an independently validated standard.
Learning outcome
Explain how moisture changes affect movement and make a documented installation-readiness decision.
Start with the service environment
Wood exchanges moisture with surrounding air. Changes below fiber saturation affect dimensions, and movement across the grain is generally much greater than along it. A shipment date or a fixed number of days onsite cannot prove that boards are ready. Consider expected seasonal conditions, current weather, storage, board dimensions and the supplier’s written guidance together.
Build a useful moisture record
Inspect packaging and storage first. Sample boards from different bundle positions, not just the easy-to-reach top layer. Use a meter suitable for the material and apply its species and temperature guidance. Record the meter, settings, board location, date and readings. Surface wetness, treatment and dense species can complicate interpretation; investigate unusual differences rather than averaging them away.
Make the decision, not just the measurement
Keep stock supported, protected and ventilated according to supplier instructions. Compare readings with expected service conditions and the installation specification. If the two disagree, pause and obtain clarification. Design gaps, fastening and drainage as a system; neither a finish nor a hidden clip eliminates wood movement. Avoid copying one universal gap or moisture target to every species and climate.
Sources & scope
These references support the underlying principles; they do not approve a specific project or endorse EHCI.
- USDA — Chapter 4: Moisture relations and physical properties of wood
Wood moisture fundamentals and dimensional behavior.
- USDA Forest Products Laboratory — Wood Handbook (2021)
Reference chapters on species, moisture, fastenings, biodeterioration and finishing; not a project-specific specification.