While light weight flooring systems are commonly used in new apartment developments in many countries, they are generally regarded as providing only moderate impact sound insulation. Poor acoustic design of a light weight flooring system can result in non‐compliance with applicable building code standards and poor perceived performance, particularly in comparison to massive floor systems which include a concrete slab. It is therefore useful to develop a reliable prediction routine, to engineering accuracy, for light weight floors. This paper briefly outlines existing theory for prediction of impact sound insulation for light weight floors. A development of the basic model is proposed, involving consideration of the modal response of the floor membrane and its potential effect on the impedance of the floor in the mid‐frequency region.