Simple empirical relationships are available in many design codes to relate the height of a building to its fundamental period of vibration. These relationships have been realised for force-based design and so produce conservative estimates of period such that the lateral shear force will be conservatively predicted from an acceleration spectrum. Where assessment of a structure is concerned, however, it is the displacement demand that gives an indication of the damage that can be expected; this displacement would be underestimated with the use of the aforementioned period-height formulae. Furthermore, the period of vibration of interest in assessment is the yield period, which is calculated using the yield stiffness, also often referred to as the cracked or elastic stiffness. The derivation of a yield period-height formula for use in displacement-based assessment of European buildings is thus the focus of this work. Analytical fibre element models of RC frames of varying height have been developed and the yield period has been sought using eigenvalue, pushover and dynamic analyses.