The overall aim of our research is to eventually develop a viable system, using pinus radiata, for demountable multi-storey timber buildings up to 6 storeys with sound insulating floors. The components are to pack efficiently into containers and be easily transported. This paper describes the proposed demountable multi-storey timber building system. Also, it reports on the testing of a prototype floor, with radiata pole joists, for sound insulation properties. Measurements have been made of the objective performance and complemented by subjective comparisons made in a purpose-built International Electro-technical Commission listening room. The results indicate that the floor meets code requirements – even when it has a hard surface.