Historically timber-framed floor system designs have sometimes included some sort of granular material infill in order to reduce sound transmission between tenancies. Often this material is readily available and low cost material (e.g. ash, scoria, and sand). Recent research has been conducted into timber-framed floor toppings which contain a granular material infill in the form of a sand and sawdust mixture. The sand and sawdust infill increases the mass of the floor, which improves the low frequency impact insulation performance. This sand and sawdust infill also greatly increases the vibration damping in the upper part of the floor, improving the mid to high frequency sound insulation performance, while also making the system robust to construction defects. This paper presents results of isolated element impact insulation and flanking transmission measurements of timber-framed floors which have a sand and sawdust infill in the floor topping.