Learn what the waterproofing bathroom standards are in Australia and what can be done to protect your home from a poor waterproof installation.
Ask the Inspector, Building Inspection Tips, Building Inspections, House Interior Wet Areas

How Do You Know a Bathroom Meets Australian Waterproofing Standards?

Open Home Check: Signs the Bathroom Waterproofing Doesn’t Meet Australian Standards 

A common recurring building defect reported by property owners in newly acquired or renovated homes is the waterproofing. Bathroom areas with insufficient waterproofing are a water damage headache just waiting to unfold. 

The quality installation of waterproofing a bathroom will determine its longevity in the home. 

To put it simply, a bad waterproof job can cause an array or problems, but the most troublesome is the premature renovation of a bathroom. It costs money and time to fix – and bathrooms aren’t the cheapest rooms in the home to renovate.

The only way to fix a bathroom with significantly leaking floors or walls is often to do a full renovation.  This may involve removal of debris, and then getting the room back to square one where the waterproofing can be installed to Australian standards.  

There are some epoxy treatments which can be applied over the tiled wall and floor, but these are only a temporary fix. 

A poor waterproofing membrane is often due to it not being installed according to Australian standards by a licensed waterproofer. 

So what is the Australian standard for waterproofing and how can you prevent the upheaval of a bathroom renovation to rectify waterproofing issues?

What is waterproofing?

The first question to address is what waterproofing is. 

Many renovators may not be familiar with waterproofing but it’s the most important aspect to protect the home from structural damage should water find its way into places it shouldn’t be. 

The first step when building or renovating a bathroom is to have a waterproof barrier installed around the walls and floors. This barrier protects the structure of the property from moisture. 

The installation of waterproofing must abide by the Australian standards. It’s not a DIY project for the unfamiliar. 

What are the Australian standards for waterproofing bathroom areas?

Waterproofing a bathroom must comply with the Building Code of Australia and Australian Standards AS3740-2010 Waterproofing of wet areas in residential buildings. 

While your licensed waterproof specialist will know these Australian standards, it’s good for the property owner to know the minimum requirements. 

It can’t hurt to go above the minimum requirements too, if the property owner is wary of water damage. The cost of installation compared to the costs of water damage can be significantly less. 

If a bathroom is installed on a ground floor, the shower floor and walls must be waterproofed up to 1800mm. The walls encasing the bathroom must be waterproofed up to 150mm. Hobs should be waterproofed up to 100mm.

Wet room bathrooms (bathrooms with frameless showers) will need to have the whole bathroom floor waterproofed as well as the walls up to a 1500mmradius.  The same minimum requirements for a shower would need to be installed for the shower space in a wet room bathroom. 

Wet room bathrooms are a modern style and very popular in renovated bathrooms. It’s paramount the waterproofing is done correctly to prevent water damaging the property in the future. 

If a bathroom is on the second floor or higher, the whole floor must also be waterproofed. The same requirement is applicable for bathrooms with timber flooring. 

Can you waterproof a bathroom yourself?

Your locality will determine if you can waterproof the bathroom yourself or engage with a professional service. Even if your locality states you can waterproof a bathroom yourself, it’s highly recommended to use a licensed waterproof installation specialist. 

In Queensland and New South Wales, a bathroom must be waterproofed by a technician with a current and valid waterproofing license. 

In other states in Australia, a compliance certificate must be given by the waterproofer to assure the waterproofing has been installed to Australian Standard AS 3740.

A qualified waterproofer will have completed a Certificate III in waterproofing. They will also offer a guarantee for the work they have completed in your bathroom and have insurance for the work they have completed. 

When it comes to waterproofing a bathroom, it should be done by a qualified waterproofer even if local requirements state you can apply it yourself. 

Local and state laws can be contradictory and they can also change. Your new bathroom may not meet waterproofing Australian standards when it’s done as a DIY job. The question needs to be asked if you’re saving money now on your renovation, what extra costs are you creating in the future if you haven’t installed it correctly? 

Waterproofing problems

The common waterproofing problems in homes have occurred due to installation or lack-there-of. A leaking bathroom is a certainty. Here are the common waterproofing problems to avoid.

  • Not ensuring the waterproofing is applied in the correct sequence of the bathroom renovation. The application is done before walls and floors are laid with their final finish. 
  • Not choosing the correct waterproofing product for the application.
  • Not allowing enough time for the waterproofing to cure.
  • Not installing waterproofing in mandatory areas of the bathroom or at the required heights.
  • Skipping waterproofing altogether. 

The best way to avoid these common waterproofing problems is to engage with a licensed and insured waterproofer. They have the experience and knowledge when choosing the correct product and installation for your bathroom type. 

How do you waterproof a bathroom floor in Australia

The best way to explain how to waterproof a bathroom floor in Australia is that it’s done in stages. There are different applications or systems installed to prevent water travelling through various orifices and surfaces of the bathroom. 

Before the bathroom is built, waterproofing will be applied under the floors and walls. A bathroom membrane is the most common type of waterproofing. The steps involved in waterproofing a bathroom floor are as follows:

  1. The wall and floor surfaces of the bare bathroom space will be cleaned and primed.
  2. A waterproof membrane agent will be painted or sprayed.
  3. Curing time will be needed for the membrane to dry. 
  4. Floors and walls can be sheeted/tiled. 

Liquid sealant will be applied to the tiles to establish a protective barrier to water seepage. 

Silicone is then used to seal the gaps where the tiled floor and walls meet to prevent water running in behind gaps. 

What are the costs of getting a bathroom waterproofed?

The costs can vary when getting a bathroom waterproofed. Much of the cost is determined by the size of a bathroom and whether it’s a wet room or has concealed sections like an enclosed shower requiring less application. 

The best way to determine the costs is to get a quote from a qualified and insured waterproofer. Costs can vary between states too. Waterproofing can cost from $40 per meter. For an average sized bathroom, you can expect to pay between $500 – $1000.

Signs a bathroom has bad waterproofing

The signs a bathroom has had a bad waterproofing application include:

  • Dripping of water under a shower or water seepage around wall and floor structures
  • Water damage to timber studs and structures attracting termites
  • Mould and mildew growth inside walls and on floors
  • Squelching or movement of tiles when stood on

There are two options to fix a bad waterproofing application. 

  1. An epoxy treatment can be applied to the tiles on the floor and wall to create a protective barrier to moisture and water.
  2. Demolish the bathroom by ripping up tiles and clearing the wall and floor surfaces so the waterproof membrane can be applied again. 

Is waterproof laminate flooring REALLY waterproof?

Waterproof laminate floors are an attractive product to use in bathrooms due to its cost effectiveness and look. But is it really waterproof?

The click-lock system and water resistant technology in laminate floors advertise that waterproofing is not necessary with this product installation. The surface is 100% waterproof but the warranty is shortened compared to a tiled surface. 

Most waterproof laminate floors have a 5 year wet warranty which means you will need to replace this flooring sooner rather than later. 

Do you need to waterproof a bathroom floor if it’s concrete?

It is recommended to waterproof a bathroom floor when it’s concrete. Concrete is porous and water-resistant, but it’s not waterproof, therefore it requires the same waterproofing installation as other flooring types. 

Waterproofing would not be a common building defect if more consideration was given to the choice of installer and application. 

For peace of mind when purchasing a home, get in touch with Andrew and the friendly team to arrange a building inspection.


About Andrew Mackintosh

Andrew Mackintosh has been answering home inspection questions in the greater Brisbane area since 1995. He has personally carried out over 20,000 building inspections and is a licensed builder and licensed building inspector, Member of Queensland Master Builders Association & Institute of Building Consultants. Being the business owner and the inspector, Andrew is passionate about providing clients with excellent customer service, value for money, honest, unbiased, thorough inspection and reporting in a professional and timely manner to allow clients to make informed decisions when purchasing property.

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