The global stiffness behaviour of modular-based two storey timber structures was studied under prescribed horizontal displacements at the upper corners of the volume modules. To be able to study this behaviour, a numerical finite element model was created in Abaqus. A parametric study was performed in which the geometry and spring stiffness of joints were varied until the enough stiff module was attained for safe transfer of shear forces through the module structure. The FE-model was parameterized to have possibility to vary positions of door and window openings in the volume modules. These openings had influence on the global structural behaviour of the two storey module structure since the side wall with two openings showed less reaction forces at its top corner point A compared to the other wall point B. In addition, the module#3 was assigned with small spring stiffness in x-direction representing friction in the joint between the volume modules. This was done without uplift plates and angle brackets. The findings showed that there was significant slipdeformation between the volume modules and small reaction forces at points A and B. The spring stiffness value in x-direction was varied until large value was obtained which resulted in overall shear deformations of the walls in both volume modules. When the angle bracket and the uplift plates were introduced between the modules when small spring stiffness along the joint between the volume modules was used, the results showed that most of the shear forces were transferred through the angle brackets instead of the fastener joints between the modules. Moreover, the results showed that the reaction forces at the points A and B increased when the angle brackets were assigned in the module. Furthermore, the results also showed that uplift plates used in the model worked well for simulations with low vertical spring stiffness between the modules.