Australian Waterproofing Standards (AS 3740) – Key Element in Residential Homes

August 14, 2020
Australian Waterproofing Standards (AS 3740) – Key Element in Residential Homes

When we talk about quality homes in residential construction, there  are very critical aspects which contribute to this  and the prolonged life of your home structure. 

A key element that is often  missed out is Waterproofing. Leaks or damages due to water penetration can not only weaken your structure but may pose serious implications to mould, dampness or damages to other building materials or structures within a home. All Australian Homes need to comply with AS3740 standards to meet waterproofing requirements in wet areas such as bathrooms, laundries and balconies.

What is Waterproofing and why do we need to do it?

Waterproofing is one the first steps that is taken into consideration whenever a wet area such as the bathroom, laundry or a balcony is built. It involves installing a waterproof barrier or a physical barrier to walls and floors to prevent moisture penetration through the structure of your home. It’s Either your bathroom is fully compliant with the waterproofing requirement or it is not. Waterproofing can be done in three simple steps.


STEP ONE – Primer Application

Prime the walls and floors and make sure there are no large gaps between them

STEP TWO – Close gaps

Use a bond breaker, usually made of rubber or fabric, that aid in closing gaps in the most important areas such as corners, drains or round drain fittings. 

STEP THREE – Membrane application

Lock membrane layers by applying two coats horizontally and vertically 

What is the Australian Standard or requirements for waterproofing (AS 3740)?

The Australian construction standards follow certain rules for the construction of residential buildings. Buildings should adhere to this standard, by all means, to become inhabitable. The standard of waterproofing the wet areas of a building is called the Australian Standard 3740 or AS 3740.

There are various areas in apartment buildings that are prone to collecting moisture over time. Open areas may have walls and floors which may be exposed to moisture due to rainfall. Inside houses, kitchens and bathrooms are constantly exposed to moisture from taps, washbasins, and drainage outlets.

The Australian Standard AS 3740 is made in regard to maintaining the structural integrity and hygienic conditions of a building for the long run. Not waterproofing building areas can lead to fungus, mold which can lead to various hygienic issues.

If AS 3740 is not followed, even the concrete may get eroded due to excessive moisture. If the metal frames beneath the concrete catch moisture, they may rust and cause structural damage. 

AS 3740 directs certain standards to coat concrete, rust-proof the metal frame structures beneath the concrete, and also take different waterproofing measures to keep exposed surfaces like bathrooms, kitchens, and wash areas free from micro-bacterial and fungal buildups.

It is also important to make sure the drainage and the water outlets are optimized to carry out water from the building without retaining anything. 

The key requirement is to meet the Australian Waterproofing Standards AS 3740 and Building Code of Australia guidelines. The regulations mainly depict the following minimum requirements:


  1. According to Australian Waterproofing Standards AS 3740, all shower floors must be waterproofed and all shower walls to be at least 1800mm should be waterproofed
  2. All other walls such as the laundry wall must be waterproofed up to 150mm. 
  3. If the bathroom floor is made of particle boards or wood or located on the second level, it is necessary for the whole bathroom floor to be waterproofed. 
  4. If any step-downs to floors are about 100mm, it should be waterproofed as well. 


It is good practice to follow these minimum Australian Waterproofing Standards (AS 3740) requirements. However, depending on your situation and needs, you may also waterproof the areas around the bath, toilet, vanity units, and other possible water penetrating points.

Who is qualified to do waterproofing in Australia?

Only trained professionals who currently carry an Australian waterproofing license especially in NSW and QLD are qualified. Said professionals must provide a statement of compliance once the job is done. This is an indication that the work they have done complies with the Australian Standard AS 3740 – Waterproofing of domestic wet areas. In most cases, a qualified person or license holder would also have an approved III level course certification in waterproofing.

What does BuildQ Group do to meet these Australian Waterproofing Standards (AS 3740)?

BuildQ Group takes waterproofing and moisture penetrations very seriously because of their great effect on structure quality and significant impact on the building process. First and foremost, only licensed and qualified trades are used to meet all BuildQ Groups wet area waterproofing requirements.

Prior to doing any waterproofing, supervisors or site staff arrange a meeting with a waterproofing technician to make sure that the areas are ready for waterproofing. We make sure the areas are clean and free from dust. All penetrating junctions should have no gaps, or all gaps are silicone with approved sealants.

Our new approach to waterproofing begins with our PVC products range that overcomes all the shortcomings of a surface applied coating system.

The membrane material is PVC transparent plastic polymer material which is designed to make drainage and sewer pipes. It is applied to the shower walls and the perimeter of the bathroom walls that reach up to a height of 1800mm.

Then, a PVC floor membrane is laid on the floor and a PVC shower tray is fitted with plastic welding and all joints overlapped with plastic welding and silicon sealed.

A water stop angle is also established at the entry point of wet areas. The PVC floor membrane is turned into penetrating pipes or floor wastes, to make sure no water can penetrate the floors.

The PVC floor membranes are 1.5mm thick, light grey, and available with or without fleece backing, allowing for all types of installation including bonded, loose laid, ballasted, or mechanically-fastened applications. It’s environmentally friendly, recyclable, and UV stable. 

Why does BuildQ Group use PVC membranes?

The system has no reason to fail based on the following facts:

  • P.V.C. sheet membranes are class III flexible membrane systems, which unlike liquid applied membrane systems have uniform thickness and are not subject to applicator oversights. They also are not subject to emulsifying and or pitting, as are acrylic and polyurethane membrane systems, if not correctly primed.
  • P.V.C. sheet membranes are a single layer application and do not require primers. Our P.V.C. sheet membrane applicators are highly skilled and have been in the industry for more than 15 years.
  • The installation of P.V.C. sheet membranes do not give off any odours or toxic fumes. P.V.C. sheet membranes do not require curing time, hence quicker turn around. A huge advantage in cold or damp climates.
  • The membrane can be tiled over immediately upon completion of the installation.The average time to install a P.V.C. sheet membrane in a bathroom is 3-4 hours
  • P.V.C. sheet membranes are unaffected by household cleaners.

Benefits of using PVC membrane:

  • Resistance to wind stress.
  • High resistance to weathering and ultraviolet rays.
  • High mechanical resistance.
  • Insensitivity to the hot-cold cycles.
  • Resistance to puncturing.
  • Possible RAL color for landscape or architectural purpose

A quality waterproofing system does not only give you peace of mind at home but ensures your home is free from any moisture or water penetrations. It is the most critical element to achieve protection from leaks and water damage which can result in furniture, floor covering, walls and structural damages. Water damage can lead to severing the integrity of the structure, making it unsafe to live in. So in conclusion, good quality PVC waterproofing membranes extends the lifespan of a home by limiting moisture which may intrude or cause rust, rotting or corrosion defects to the members. It will also protect from mould and provide a healthier environment. The overall impact will reduce maintenance costs and increase the property value. This is what BuildQ Group believes in delivering quality homes.