A common defect: leaking bathrooms and wet areas

Despite advances in material application and technology, waterproof ‘membranes’ or wet seals used in residential construction are prone to fail. There is a high incidence of water leaks typically to showers but also other wet areas such as around baths and laundries. 

Approximately 25% to 30% of showers in bathrooms leak!

The Building Code of Australia has differing performance requirements for different areas exposed to moisture, depending on the configuration of bathroom fixtures (such as shower screens, hobs, floor waste, floor levels and use of space. Wall and floor surfaces may be deemed either ‘water resistant’ or ‘water proof’ depending on associated risk and level of use.  

Logically, a tiled shower recess is considered ‘high risk’ and the FLOOR is fully waterproofed to a height of 150mm, waterproofed internal junctions to a height of 1800mm and all penetrations for taps and shower heads are also fully sealed.  SHOWER WALLS have a reduced risk and are water resistant to a height of 1800mm.

A failed wet seal is considered a MAJOR defect.

The wet seal is a synthetic flexible membrane typically applied by brush or roller and reinforced in corners and penetrations with a breaker bond material to help prevent a tear or breakage in the wet seal. Likewise there are requirements for SUBSTRATE materials in wet areas to floors and walls to be water resistant.


With large building suppliers now stocking wet seal products for the DIY market and home owners undertaking renovations themselves, there is an increased risk of failure of wet area waterproofing.  It is highly recommended that a Certified and Licence Construction Waterproofing specialist undertake all work with the benefit of work covered by Industry and Statutory Warranty periods (typically 5 to 7 years). For recently built or renovated works, it is recommended you obtain a copy of the Warranty from the Vendor.

Misinterpretation of findings? The importance of an experienced and qualified building inspector.

A moisture reading in wet areas!!.. but is it a MAJOR or a MINOR defect? 

There is a big difference in cost and rectification, but also complication for Purchaser, Vendor, Sales Agent and Conveyancer if the findings of elevated moisture readings are misinterpreted.

Some examples of consideration for due process to formulate a correct assessment:

  • If the tiles are not fully embedded in the adhesive layer water can accumulate behind the tile but inside the wet seal membrane: this is considered a MINOR defect.
  • In older properties the extent and location of the wet seal often cannot be determined.
  • Has moisture penetrated through to underlying wall or floor substrate?: if so this is considered a MAJOR defect.  What is the extent of damage? Is an invasive inspection required?
  • Are there areas where moisture readings cannot be taken such as 
  • to the underside of floors?
  • to the interior walls outside of the wet areas?
  • the exterior walls outside of the wet areas as these are cavity walls?
  • Are falls away from doors through habitable areas correctly configured? 
  • Are falls to floor waste sufficient to avoid ponding and potential slip hazards?

Ensure that the building inspector you engage is able to make a rigorous assessment of the issues.

+ado building inspections have over 25 years of experience in building and construction industry with in depth knowledge of building codes, standards and practices, building physics, construction method, as well as heritage conservation and restoration.


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