Floor wastes are to be installed in bathrooms and laundries in Class 2 and Class 3 buildings and Class 4 parts, where those bathrooms and laundries are above another sole-occupancy unit or public space. F2D4(2) requires that the floor containing these mandatory floor wastes be provided with a fall.

The aims of F2D4(1) are to minimise water overflows from fixtures in the specified rooms:

• causing costly and possibly dangerous water damage to other sole-occupancy units;
• creating unhealthy conditions in public spaces in buildings; and
• disrupting and intruding on neighbours in the unit below.

Further, F2D4(2) requires a fall towards any installed floor waste, even floor wastes not required by F2D4(1), F2D3(1)(a)(b) or any other NCC provision.