Wood, due to its hygroscopic nature, is dimensionally unstable, which leads to swelling, shrinkage, and internal stresses in products. In this study, we investigated the hygroexpansion of spruce wood and wood-based panel composites (particleboard, fibreboard, and plywood) using conventional mass and dimensional measurements as well as digital image correlation (DIC) photogrammetry. A total of 60 specimens were conditioned in a dry climate (φ = 33%) and a humid climate (φ = 75%), and were then dried to an oven-dry state. The results showed that spruce wood was the most hygroscopic and dimensionally unstable material, particularly in the radial and tangential directions. Plywood proved to be the most stable in all directions, while fibreboard was stable in-plane but exhibited significant thickness swelling. Particleboards achieved intermediate values, with the fire-resistant board being more stable than the standard and moisture-resistant boards. DIC enabled precise detection of local deformations that were not captured by conventional methods, particularly along the specimen edges. The study confirms the applicability of DIC for monitoring dimensional changes in wood and composites and highlights the advantages of panel products when used in environments with fluctuating humidity.
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