D.I.Y or professional applicator?

The rules about who can complete waterproofing fluctuate slightly between different Australian states and territories. In both Queensland and NSW, the person completing the waterproofing in your home, is required to carry a current waterproofer’s licence. In other states, waterproofers must provide a statement of compliance once the job’s done, indicating that the work they’ve completed complies with Australian Standard AS 3740 – Waterproofing of domestic wet areas.

To become a qualified waterproofer, a person must be properly trained in how to apply waterproofing systems, in accordance with Australian Standards. In most cases, this will involve undertaking a Certificate III training course in waterproofing.

You will need a qualified, experienced, or endorsed Waterproofer to waterproof your bathroom, balcony, retaining wall, fish pond, roof etc. While you can get a tradesperson who specialises exclusively in waterproofing, in some instances other tradespeople may be licensed or certified waterproofersaswell.

Their work should end with a written/signed guarantee of workmanship and a warranty, so make sure you obtain these items when the job is complete. The person doing your waterproofing will have a good knowledge of the range of waterproofing products and their applications, and they should be able to explain how it works, if you’d like specific details on how your bathroom will be sealed.

Even if local regulations permit you to do the work for yourself, waterproofing can be a messy, costly experience and if it’s completed incorrectly, can lead to a myriad of issues, ranging from creeping mould infestations, to baths crashing through floors. If you’re looking to cost cut or to get involved, DIY waterproofing is definitely not the area for you!

How is waterproofing applied?

Waterproofing is best done in stages. Some of it will need to go down before the floors and walls are fully laid, some of it will need to go down after everything is in place, including the paint. Perhaps most important areas are where the walls meet the floor. Any gaps where water can seep in can cause major structural damage, which is hugely expensive to repair.

Liquid membranes are normally applied in a comparableapproach to paint. A primer is used first, then a first coat is applied horizontally. The ensuing coat is then applied vertically, in order to fill any pin holes missed in the first coat. Silicone sealants are applied around the joins where bathroom features, such as the bath and vanity unit meet the walls, to ensure water doesn’t travel behind them. Waterproofing products usually need about a day to dry, so as to ensure that they create a proper seal – and they shouldn’t be disturbed at all while they’re curing.

Waterproofing rules and regulations

There are regulations in place that your waterproofing will need to comply with, as set out by the Building Code of Australia and Australian Standards (AS 3740-1994). In short, they require that:
• In the shower, the whole floor must be waterproof and the shower walls should be waterproofed up to 1800mm.
• The walls need to be waterproofed up to 150mm.
• If the bathroom floor is made of, or contains wood, or if the bathroom is on the second story or higher, the whole floor must be waterproofed.
• Over the step down to the floor should be waterproofed to 100mm.

Of all the rooms in your home, you will need the bathroom to be the most waterproof. Waterproofing is one of the first steps to take place when a bathroom is being fitted out. It involves installing a waterproof barrier around the walls and floor in your bathroom to protect the structure of the house from moisture. Waterproofing installation recommendations are black and white; your bathroom is either sealed, or not sealed.


Waterproofing systems and their installation details shall be waterproof or water resistant as required by the BCA. In addition, waterproofing systems and their installation details shall be compatible, and shall resist the following:

(a) Differential movement due to—

(i) Actions as defined in AS/NZS 1170.1 and AS/NZS 1170.2;
(ii) Shrinkage and expansion of substrate materials, framing and finishes;
(iii) Temperature variations from 5°C to +50°C; and
(iv) Movement tolerances as defined in AS 2870.

(b) Exposure to—

(i) Cleaning chemicals [such as detergents, sodium hypochlorite (bleach)], as required by AS/NZS 4858; and
(ii) Alkalis from cement mortar as required by AS/NZS 4858.


The waterproofing system shall accommodate the expected movement at movement joints in the substrate.

Water-resistant substrates

For the purposes of this Standard, the following materials used in waterproofing systems, in conjunction with water-resistant surface materials in accordance with Clause 2.4.3, are deemed to be water resistant:
(a) Walls:
(i) Concrete in accordance with AS 3600, treated to resist moisture movement.
(ii) Cement render treated to resist moisture movement.

NOTE: For recommended practice, see HB 161, Guide to plastering.
(iii) Fibre cement sheeting manufactured in accordance with AS 2908.2.
(iv) Water-resistant plasterboard sheeting manufactured in accordance with

AS/NZS 2588. (v)Masonry in accordance with AS 3700.


Concrete in accordance with AS 3600 and AS 2870.

(i) Compressed fibre cement sheeting manufactured in accordance with AS 2908.2.

(ii) Fibre cement sheeting manufactured in accordance with AS 2908.2, and
supported on a structural floor.

(iii) Flooring grade particleboard sheeting manufactured in accordance with
AS/NZS 1860.1, and installed in accordance with AS 1860.2.

(iv) Structural plywood manufactured in accordance with AS/NZS 2269, and
installed in accordance with AS 1684.2, AS 1684.3 and AS 1684.4.


Where required, falls in floor finishes shall allow all surface water to drain without ponding except for residual water remaining due to surface tension.
For general bathroom floor area, the minimum fall to the waste shall be 1:100.


Falls in shower floors shall be sufficient to prevent—

(a) surface water from being retained on the shower floor (except for residual water remaining due to surface tension); and

(b) water from discharging outside the shower area.

For shower areas with a vertical separation between the shower area and the wet area, such as a shower screen, hob, step-down or water stop, the fall to the waste shall be 1:100.

As a minimum for other shower areas, the fall shall be a minimum of 1:80.

The primary consideration for falls in floor finishes is to ensure water does not remain on the finished floor in a manner that can adversely affect the health or amenity of the occupants or deteriorate building elements.
Falls in floor finishes should ensure water exits the area at the floor waste or doorway if that is the designed exit point (e.g., laundry door to exterior). Water should not pond on the floor, with the exception of residual water remaining due to surface tension.

The ratio of fall achieved in a floor may vary depending upon the—

(a) finished height requirements at doorways;

(b) height of fixtures or fittings;

(c) Dimensions of the tiles used, adequate falls become more difficult to achieve as the size of the tiles used increases;

(d) Area of the floor to be drained; and

(e) Requirements of persons with disabilities.

Clause 3.4 specifies a fall ratio of 1:100 in shower areas.
Where falls flatter than 1:100 are proposed, the effectiveness of the floor drainage should be confirmed to ensure the primary consideration given in Paragraph B1 has been met.

Materials shall be cured adequately for their intended use.
NOTE: The membrane should be protected from physical and/or chemical damage until covered by the finished surfaces.


3.7.1 Baths to be recessed into a wall

Baths recessed into a wall shall have an integral vertical upstand lip along the side of the bath walls to enable a waterproof junction between the bath and walls.

3.7.2 Baths with a downturn lip

Baths without an integral upstand but with a downturn lip shall be installed as an insert bath, as specified in Clause 3.8.

3.7.3 Baths without an integral edge to allow for a vertical upstand for termination of waterproofing

For baths that do not have an integral edge detail to allow for a vertical termination of the waterproofing, there shall be full waterproofing of the walls and floor area and waterproofing under the bath. The enclosed space under the bath shall be ventilated.

NOTE: Ventilation is required to allow evaporation of water leaking around the edge of the bath into the enclosed airspace under the bath.


3.9.1 Perimeter flashing

The following list specifies the minimum requirements for the treatment for various junctions. Junctions may be either wall to floor or wall to wall. Either the floor or wall may be waterproof, water resistant or have no treatment specified.

The types of junctions that shall be used are as follows:

(c) Type 1

Where waterproof to waterproof surfaces meet, the waterproofing shall be
continuous across the junctions and, where required, incorporate an appropriate bond breaker.

(d) Type 2

Where waterproof to water-resistant surfaces meet, a bead of sealant shall be
deemed to be a waterproof junction.

(e) Type 3

Where water-resistant to water-resistant surfaces meet, a bead of sealant
shall be deemed to be a water-resistant junction.

(f) Type 4

Where non-water-resistant to water-resistant surfaces meet, a bead of sealant
shall be deemed to be a water-resistant junction.

(g) Type 5

Perimeter flashing to wall/floor surfaces shall be continuously sealed to the
horizontal surface and have a vertical leg of a minimum of 25 mm above the finished floor level, except across doorways, and the horizontal leg shall be a minimum width of 50 mm.

3.13.7 Bond breaker installation for bonded membranes

Bond breakers shall be included at all wall/floor, hob/wall junctions and at movement joints where the membrane is bonded to the substrate. Bond breakers shall be of the type compatible with the flexibility class of the membrane to be used.


1 For appropriate bond breakers, see Table 3.2.
2 Typical details for bond breakers are shown in Figure 3.7.
3 Additional information on bond breakers is given in Appendix A.



Membrane class Elongation at break Minimum bond breaker/tape width to bridge joints opening up by 5 mm.
I <60% 75 mm with backing rod II 60% to 300% 35 mm III >300% 12 mm

1. Bond breakers for Class I membranes (low extensibility) allow the membrane to flex rather than stretch.
2. Bond breakers for Class II membranes (medium extensibility) allow the membrane to stretch. If a tape is used as a bond breaker, either the membrane will not bond to the tape or the tape will have elastic properties similar to the membrane; for example, for a Class II membrane, a 35 mm wide bond breaker/tape should be applied over a joint to accommodate the joint opening up by up to 5 mm.
3. Bond breakers for Class III membranes (high extensibility) allow the membrane to have even thickness.