When is a Fixture Floor Drain Not Floor Waste Gully

The National Construction Code 2022 defines a floor waste as ‘a grated inlet within a graded floor intended to drain the floor surface’. AS/NZS 3500.2:2021 provides for a shower outlet to act as a floor waste gully (FWG) under certain conditions. The NCC defines a wet area as an area within a building that is supplied with water from a water supply system, which includes bathrooms, showers, laundries and sanitary compartments.

In QLD and various other states, a floor waste is not mandatory in a Class 1 building. A floor waste gully can be installed internally in a wet area in a Class 1 building with provision, where required for the connection of waste pipes from fixtures and for the entry of water spillage from floors.

A shower recess installed with a water stop as defined by AS 3740 and commonly referred to as a ‘hob’ does not provide for any spillage from a bath, basin, or other waste fixture installed in the same wet area to be captured and drained to the shower outlet. Where the shower recess is enclosed by screens or walls intended to contain the spread of water within the shower space, the outlet cannot be considered a FWG for the purpose of receiving the discharge from other fixtures but rather as an individual fixture waste outlet. A separate FWG can be installed in the associated wet area for the purpose of receiving the discharge from other waste fixtures located in the same room.

Where a floor waste gully is to be installed in a Class 1 building for the purpose of receiving discharge from permitted waste fixtures as well as providing for drainage of spillage from wet area floors, the installation shall satisfy the performance requirements of the NCC Volume 1 – 2022.

F2P1 Wet area overflows

Overflow from a bathroom, laundry facility, or the like must be prevented from penetrating to:

1. another sole-occupancy unit used for sleeping accommodation; and
2. a public space

F2D4 Floor wastes:

1.  In a Class 2 or 3 building or Class 4 part of a building, a bathroom or laundry located at any level above a sole-occupancy unit or public space must have a floor waste.
2. Where a floor waste is installed—
   • the minimum continuous fall of a floor plane to the waste must be 1:80; and
   • the maximum continuous fall of a floor plane to the waste must be 1:50.

For further questions and technical advice, MPAQ members can call the Technical team on 07 3273 0800.