We studied the correlation between the thickness swelling and the layer strength of wood composites, or what impact the adhesiveness of the building blocks has on the swelling of the boards. We tested LSB and MDF boards, particleboards type P2 and particleboards type P5. We tested layer strength and thickness swelling. Thickness swelling was determined by immersion in water, exposure to an environment with increased humidity (relative humidity 85 %, temperature 20 °C), and cyclic exposure (immersion in water, freezing and drying). When the test was completed, layer thickness swelling and sturdiness of the test samples were determined. We established that in the dry state, LSB panels have the best layer strength, whereas the particleboards type P2 have proven to be the least effective. When exposed to a humid climate, particleboards type P5 showed the smallest swelling, whereas MDF boards had the highest thickness swelling. When immerging under the water, LSB boards showed the smallest thickness swelling, while particleboard type P2 the largest. We also performed a cyclic test, where we found that the proportions of layer strengths were similar as those with the dry boards, as well as thickness swelling with the exception of MDF boards. The latter had smaller swelling due to the drying, which was the last step of the cycle. The fibreboard namely submits the moisture quicker than other boards because fibres have the great ability of absorption and dissipation of moisture, which is why the board very rapidly responds to a climate change of the surrounding area.