Faulty waterproofing is one of the three top building defects in Australia; and the main areas it affects are balconies and bathrooms (showers and floors etc). Did you know that when it comes to high-rise apartment blocks in Australia, failed waterproofing is the most common defect nationally! A recent industry report showed that the total cost of building defects in the last decade amounted to an eye-watering $6.2 billion, with weather and water damage issues accounting for $1.4 billion of that total!*

Usually, waterproofing represents just a couple of percent of the overall construction costs for a property, and yes, if not done correctly the repair and remediation costs can blow out into the tens of thousands of dollars.


There are three main reasons why waterproofing tends to fail:


1. Poor workmanship, especially when it comes to preparation accounts for 90% of all waterproofing failures.

2. The second most common problem is the failure to prime the surface areas correctly before the application of the waterproofing membrane.

3. The third most common cause of leakage is when there is a failure to test the concrete of the mortar floor or walls before applying the waterproofing. In simple terms, this is all about how much residual moisture there remains in the floors, walls, concrete, or mortar.




It can be a very technical space to understand, however, there are a few basics which can ensure the risks are minimised:


This is the most effective solution to prevent waterproofing issues, but one that is often overlooked.

Example 1 – Showers without hobs

Whilst these look awesome, it’s amazing how often I come across these as being unpractical after they have been built.  If you want to have a hob-less shower, you need plenty of fall in the tiled floor to ensure that the water doesn’t run out of the shower area and across the bathroom floor. Jargon Buster – Don’t know what a “hob” is?  The shower hob is the little raised wall or step that goes around the shower base.  It has the important job of saving your bathroom floor from flooding whenever you take a shower.

Example 2 – Splash Effect

Make sure you design to keep the water in the shower.  Use screens (glass screens, shower curtains, etc) to prevent splashing.  Showerheads mounted on the ceiling look fantastic but create a lot of splash; showers within baths do the same.  It’s far easier to design to prevent waterproofing issues than to try to rectify after the works have been poorly completed.


Ensure that there is sufficient drainage (ie drains in the floor or balcony etc) and that there are sufficient falls to those drains.  It’s no good having drains if they are the highest point on the floor; they have to be the lowest so that any water on the floor runs to the drain. Encourage the plumber and tiler discuss the drain grates to ensure that they are fixed properly and that there is a good seal between the tiles and edge of the drain


Use Accredited & Licensed Tradespeople

Waterproofing membranes need to be compatible with the surfaces being applied to and the adhesives being used (tile glues etc). Check the waterproofing contractor is accredited or licensed and get referrals to ensure the waterproofing is done correctly; they should also provide you with a certificate on completion of their works.

The Building Code of Australia and the Australian Standards stipulate the regulations that your contractors need to comply with. These include MINIMUM requirements but speak to your waterproofing expert to discuss what other choices you can make to protect yourself.

The rules as to who can do waterproofing may differ across the different states and territories, but the simple fact remains the same regardless of where you live: your wet areas (usually bathrooms, showers, toilets, laundries, and balconies) are either waterproof or not waterproof. There is no in-between!


*The Urban Developer: Waterproofing tops out construction concerns June 2020