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Edition 3 – Drainage & Waterproofing

The Australian Institute of Waterproofing (AIW) of which Wet-seal is a member has written an article that appeared in the State based Master Builder magazines, the article was titled “Waterproofing – Common Causes of Failure”.

This news article informs you of another common cause of waterproofing failure – Drainage.


  • Common failures are caused by poor drainage of surface moisture adversely affecting the waterproofing.
  • A builder would not install a metal or tiled roof without the minimum specified gradient for surface drainage.
  • This however is not the case with waterproofing.
    • It is still a common occurrence that waterproofing membranes are installed on horizontal surfaces without falls for substrate drainage.
    • Single component acrylic membranes were renowned for re-emulsification under saturated conditions in the 1980’s and 1990’s.  (Wet-seal does not have acrylic membranes).
  • While products have changed, the construction methods have not.
    • Nearly every part of a building exposed to surface water or conveying water has specified gradients including stormwater pipes, eave gutters, box gutters, sanitary pipes, culvert drains and kerbs.
  • A major problem of saturated mortar screeds built up for surface drainage over waterproofing membranes is salt calcification or efflorescence to tile surfaces.
    • Waterproofing ideally should be installed to a gradient that creates correct fall for drainage.
  • There is a misconception within the building industry that a PVC drainage pipe embedded in or passing through a concrete floor slab is a rain water outlet (RWO).
    • The drainage pipe is not the outlet.  Providing a waterproof seal and connection to a PVC pipe often results in failure.
    • All drainage outlets should be an RWO cast into the concrete slab and connected to the drainage pipe.
    • The RWO will provide the required flange for connecting the waterproofing membrane at the drainage point.
    • A major problem in subsurface drainage is sleeved PVC floor grate housings which are pushed into drainage pipes damaging the membrane junction and blocking subsurface drainage.
  • Whilst waterproofing is designed to protect the structure and prevent water ingress into the building there is often little consideration given to the drainage to ensure the waterproofing membrane’s performance.
  • The failure of waterproofing is often associated with poor or non-existent drainage particularly at the subsurface level.
A copy of the full article published in Master Builder magazine is available upon request.  To receive a copy of the article, please click on Request More Information and we will email you a copy.

For any other advice of a technical nature, Wet-seal’s highly experienced technical expert, Robert Rath, will be happy to take your call.  Robert can be contacted on 0413 008 303 or via email rrath@wet-seal.ws

Alternatively, please speak with your local Franchisee directly.  Details of how to contact your local Franchisee can be found at Find A Franchisee

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