Bare mass timber structural slabs have relatively low impact sound insulation performance. Though certain floating floor assemblies on mass timber slabs can provide adequate single number ratings, such assemblies are mainly effective in the middle to high frequency range. This study presents the impact sound insulation performance of raised discrete floating floor assemblies for mass timber slabs. The raised discrete floating floor assemblies were composed of elastomer blocks, insulation materials, wood-based sheathing panels and concrete topping or cement boards. Impact sound insulation tests were conducted on a mock-up building under different excitation sources including human walking, ISO tapping machine and ISO rubber ball. The results showed that raised discrete floating floor assemblies tested in this study could improve the impact sound insulation ratings of the bare slabs by up to 41 dBA under ISO tapping machine excitation. Under different excitation sources, the impact sound pressure level spectra obtainedfrom ISO rubber ball had similar frequency characteristics with that from human walking, though the magnitudes were higher at each octave band. The discrete raised floor without any mass topping had similar performance (LFmax=74.3 dBA) in attenuating low frequency sound to the continuous floating concrete topping of 50 mm thickness. The advantage of the raised discrete floor assemblies with dry solution boards over the continuous floating concrete topping assemblies based on the ISO tapping machine tests did not exist with the ISO rubber ball testing. Higher topping mass resulted in lower LFmax.