Full size wood joist floors were built and their frequencies were measured. Double tee-beam floors were built and also cut from the full size floors and their frequencies were measured. The floor joists investigated included: solid sawn, parallel chord floor trusses, and composite I -joists. The first natural frequency of each tee-beam floor was predicted after measuring the deflection under imposed loading. A design procedure is presented to predict the fundamental frequency of wood joist floors from tabulated material properties