<p>This study is aimed at investigating the effect of partial composite action between floorboards and joists on the dynamic properties of timber floor system: natural frequency, velocity and deflection due to footfall vibrations. The results are compared with the results of two cases: floor system with full composite action and floor system with non-composite action. It is shown that span length of the joists and spacing between the fasteners are the two main factors that affect the dynamic properties of floor system with partial composite action. As the floor span length increases, and spacing between fasteners decreases, the results of dynamic properties of floor system with partial composite action will approach the results of floor system with full composite action. On the other hand, as the span length decreases and spacing between nails increases, the results of floor system with partial composite action will approach the results of floor system with non-composite action.</p>