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Floor wastes in bathrooms when are they required

One of the more contentious issues in relation to bathroom construction is the provision of floor wastes and when they are required.

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 of 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.

BCA Volume 2 references or ‘calls up’ AS 3740 as a Deemed-to-Satisfy document i.e. if the provisions of AS 3740 are followed in full the solution will comply with BCA mandatory Performance Requirements. AS 3740 contains the detailed waterproofing of wet area provisions for Class 1 buildings (houses). BCA Volume 1 also applies AS 3740 to certain classes of 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

So starting with Volume 1 requirements:

For apartment buildings (Class 2 buildings), hotels, motels and boarding houses (Class 3 buildings), and residential parts of commercial buildings (Class 4 parts of a buildings), BCA Volume 1 requires a floor waste be installed in bathrooms and laundries if a bathroom or laundry is situated at any level above a sole-occupancy unit or a public space. A public space in a building would include areas such as public foyers and reception areas.

In these circumstances the floor to the room is required to be waterproof and the floor graded to the floor waste to permit drainage of the water. The required fall of the floor, the waterproofing requirements of the floor and the installation details of the floor waste are specified in AS 3740.

The intent of this provision is to provide protection from flooding to an adjoining separate units or a public area.

Class 1 buildings

So looking at the requirements in Volume 2 for a house:

For a Class 1 buildings the BCA through AS 3740 ‘requires’ a floor waste be provided within the shower area. The required fall of the floor, the waterproofing requirements of the floor and the installation of the floor waste are specified in AS 3740.

For the area outside of the shower an additional floor waste is not ‘required’ to be provided, nor is one ‘required’ to be provided in other wet areas such as in a laundry or in a WC.

For a shower over a bath if it is ‘unenclosed’ i.e. is not provided with a minimum 900 mm wide screen for the open side of the bath AS 3740 ‘requires’ an additional floor waste be provided (see Figure 1)

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Figure 1

It should be noted that these requirements are the minimum requirements only but if a designer or builder may choose to install an additional floor waste (i.e. in addition to the one in the shower area) or provide one to the floor in a laundry or WC voluntarily.

Plumbing and drainage requirements for bathrooms and wet areas

Associated plumbing & drainage requirements in the Plumbing Code of Australia:

Plumbing & drainage requirements for all classes of buildings are set out in Plumbing Code of Australia (PCA), in turn the PCA references the AS/NZS 3500 suite of standards for the detailed technical requirements for plumbing & drainage installations.

Specifically, AS/NZS 3500.2 sets out the sanitary plumbing and drainage requirements and these requirements are replicated in AS 3500.5 (Housing Installations).

AS/NZS 3500.2 contains a number of provisions relating to the installation of floor waste (gullies) in bathrooms as part of the installation of certain waste fixtures such as baths, basins, showers, laundry tubs etc.

However, it should be noted that AS/NZS 3500.2 does not prescribe that a floor waste (gully) must be installed, rather it is listed as option as part of the installation of the waste fixture(s). For example a bidet can be installed with a trap and waste pipe or with an unstrapped waste pipe to a floor waste gully.

For bath installations, AS/NZS 3500.2 contains a similar provision for the installation of a floor waste gully, in circumstances where a bath waste is unstrapped and is not accessible.

Falls to floor wastes

AS 3740 requires that a floor be graded to the floor waste and meet other compliance requirements where a floor waste is ‘required’. The required fall of the floor is prescribed in AS 3740.

HIA is aware that there are some differing views as to whether a floor is required to be graded to the floor waste where:

  • an additional floor waste is provided voluntarily i.e. it is not required by the regulations to be provided; or

  • a floor waste gully is installed as part of a plumbing and drainage installation of a waste fixture(s).

The HIA’s view on this matter is that as the provisions of AS 3740 refer to a ‘required’ floor waste and the associated falls prescribed in AS 3740 apply to a ‘required’ fall waste, if a floor waste is provided and it is not required by the BCA, AS 3740 or plumbing & drainage requirements the floor isn’t required to be graded to the floor waste.

However, as highlighted above there may be differing interpretations on this matter, therefore before proceeding with the work it is recommended that you check with your local authority or administration in relation to the installation of floor wastes.

State and Territory variations

It is also important to check with your local authority or administration for any specific State or Territory provisions in relation to the installation of floor wastes that may override the BCA or Australian Standards provisions.

To find out more, contact HIA’s Building Services team.

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