Floor Wastes in Bathrooms – Are they required?

HIA Industry Update for NHS
Approx read time: 3 minutes

One of the more contentious issues in relation to bathroom construction is the provision of floor wastes and when they are required. There is much anecdotal evidence out there in relation to this, but what are the facts?

There are two primary documents in relation to wet areas construction:

  • the Building Code of Australia (BCA)
  • AS 3740 – 2010 Waterproofing in domestic wet areas.

Both contain information on materials and methods required in relation to waterproofing bathrooms and wet areas such as WCs and laundries.

The BCA has two parts: Volume 1 for Class 2 – 9 buildings and Volume 2 ‘Housing Provisions’ for Class 1 and 10 buildings.

AS 3740 contains the wet area provisions for Class 1 buildings (houses) and residential buildings; BCA Volume 1 also applies this to other commercial buildings.

There are several things to consider in determining if a floor waste needs to be installed.

Class 2, 3 or Class 4 part of a building
In apartment buildings, residential buildings such as motels and boarding houses, and residential parts of commercial buildings, it is necessary to install floor wastes in bathrooms and laundries if a bathroom or laundry is situated at any level above a sole-occupancy unit or a public space.

The intent of this provision is to provide protection from flooding to adjoining separate units or buildings and areas outside the immediate building. These requirements apply regardless of the type of shower enclosure being installed.

Class 1 buildings
In relation to Class 1 buildings the key to when a floor waste is required is dependent on whether the shower area, which is defined in the BCA as “the area affected by water from a shower, including a shower over a bath”, is an enclosed shower area or unenclosed.

An enclosed shower area is designed to control the spread of water within the shower by a shower screen and door. An enclosed shower area does not need a floor waste.

An unenclosed shower area means an area that is open on one or more sides and can include frameless and semi-frameless shower screens. This area is defined by an arc that extends 1500mm from the shower connection at the wall.

It is important to note that a shower area needs to provide fall to the shower waste and if unenclosed the fall would need to be provided from the 1500mm arc.

If this cannot be achieved, due to design constraints, the whole or part of the floor outside the defined shower enclosure may need to be drained and in this case a floor waste would need to be installed.

Showers over baths
A shower over a bath is considered to be unenclosed unless it has a minimum 900mm wide screen on the bath.

The provision to allow showers over baths to be considered enclosed when a minimum 900mm wide screen is installed was introduced through an amendment to AS 3740 which considered that baths with showers over them provide a better ability to control the spread of water without needing to ‘fully enclosed’ .

Where a bath does not have a screen of 900mm or more the shower will be considered unenclosed and a floor waste would be required.

Falls to floor wastes
It is important to note that although a floor waste is generally not required in a Class 1 building, if one is provided, the bathroom floor must be graded to that floor waste and other compliance requirements should be met in relation to the installation of the floor waste.

It is also important to note that despite whether a bathroom is on a ground floor or first floor of a house, the wet area provisions, including installing floor wastes if required, are the same.

Diagrams to support this matter can be found in the HIA information sheet of the same name as this article.  To view this or further information about other technical matters visit www.hia.com.au or contact the HIA Building Services team on 1300 650 620.

Craig Jennion
HIA Executive Director – Hunter