IzvlečekAbstract: An important aspect of wood-based panel usability, especially for construction, load bearing purposes or when in use for longer time, is its resistance against water. The resistance against water is related to type of woodbased panel, morphological characteristics of the constituents that panel is made of, and from the resin that was used for bonding. In an experiment we used four different wood-based panels, namely MDF (urea-formaldehyde adhesive), particleboard (urea-formaldehyde adhesive), OSB (melamine-urea-formaldehyde adhesive) and beech plywood (melamine-urea-formaldehyde adhesive). All panels were immersed into water and exposed to a humid climate for 90 days. Thickness swelling, compression shear strength and shear strength were determined after 1, 5, 30 and 90 days. The results showed that the highest strength decrease was observed at immersion into water. The lowest compression shear strength after immersion into water and exposure to a humid climate was determined for MDF. The occurrence of constituent failure due to mexposure to water was demonstrated through SEM analysis.Izvleček: Pomemben dejavnik uporabnosti lesnih ploščnih kompozitov pri gradnji in nosilnih konstrukcijah je odpornost le-teh proti delovanju vode. Odpornost proti delovanju vode je odvisna od vrste lesnega ploščnega kompozita, morfoloških lastnosti gradnika, iz katerega je plošča narejena, in lepila, uporabljenega za lepljenje. Za izvedbo raziskave smo uporabili štiri različne lesne ploščne kompozite in sicer MDF (urea-formaldehidno lepilo), iverno ploščo (urea-formaldehidno lepilo), OSB (melamin-urea-formaldehidno lepilo) in bukovo furnirno ploščo (melamin-urea-formaldehidno lepilo). Vse plošče so bile potopljene v vodo in izpostavljene vlažnim klimatskim pogojem. Določili smo debelinski nabrek, tlačni strig in strižno trdnost. Lastnosti so bile določene 1, 5, 30 in 90 dni po izpostavitvi. Največja sprememba trdnosti je bila ugotovljena pri preskušancih, potopljenih v vodo. Najnižja odpornost proti delovanju vode je bila ugotovljena pri MDF plošči. S SEM slikovno analizo smo prikazali nastanek razpok in porušitve zgradbe gradnikov.