Bamboo is a plant that can be used as a renewable alternative for construction given its short rotation period, good mechanical properties, and carbon dioxide sequestration capacity. The woody bamboo species have a cylindrical geometry, and it is composed in its majority by lignin, cellulose and hemicellulose that are distributed over the parenchymatic tissue, fibre sheaths and transport vessels. The distribution of each component varies based on the height of the culm and through the wall thickness, leading to uneven physical and mechanical behaviours at different directions. Due to the hygroscopicity of bamboo, when it is subjected to variations in humidity or when in contact with water, it tends to enter in equilibrium with the environment and its cells either shrink or swells. Starting from a dry state with increasing humidity, the parenchymatic cells and vascular tubes adsorb water first and swell, after a certain moisture content, the fibres adsorption surpasses the other cells and governs the swelling behaviour of the structure. Since the distribution of fibres increases from the inner to the outer layer of the wall thickness, the uneven swelling behaviour and dimension changes can lead to cracks and reduce the effectiveness of the construction elements. An elastodiffusive model with two multiphase continuous porous media along the thickness is developed in COMSOL Multiphysics to reproduce the behaviour of bamboo in an environment with humidity variation, taking into consideration the materials variation on its hygroscopic properties and swelling behaviour. It is expected to identify the regions with higher dimensional variation and possible points of tension that leads to the appearance of cracks on bamboo poles.