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Edition 1 – Top 3 Causes of Waterproofing Failure

Below is a brief summary of some key points regarding Waterproofing – Common Causes of Failure:

  • Waterproofing makes up between 1% and 2% of the total cost of construction of a building, but accounts for up to 80% of the complaints and huge costs in rectification.


  • The single biggest cause of waterproofing failure is workmanship.  Poor workmanship would account for 90% of all failures in waterproofing.
  • The waterproofing membrane is only as good as the surface on which it is applied or installed.  Builders have a large responsibility here.
    • Has the surface been constructed with falls for drainage?
    • Is the surface smooth and clean?
    • Is the surface free of formwork distortions, voids or protrusions?
    • Is the surface spoiled by previous trades debris and residues?
    • Has the surface been scraped and vacuumed?
  • Consistently there is insufficient time allowed in the conduct of waterproofing for the correct preparation before the application of the waterproofing membrane.
    • This is critical for the installation of the various ancillary and core parts of the waterproofing.  This may include the correct installation of waterstop angles, perimeter flashings, vertical flashing angles, pressure strip flashings, chased drop flashings, fillets and bond breakers at coves, control joints, drainage flanges, cavity flashing downturns, topping screeds for falls for drainage, reinforcing at junctions, overflow devices, linear strip drains and slip joints over suspended sheet flooring systems.
    • There appears to be a consistent failure by both Builders and Waterproofing Contractors in allowing sufficient time for preparation and installation of critical ancillary parts of the waterproofing.


  • The second most common recurring problem, after poor surface preparation, is the failure to prime the respective parts and surfaces before the application of the waterproofing membrane.
    • Failure of the waterproofing bond to substrates is a recurring and consistent problem often associated with poor subsurface drainage and saturation of tiling or topping screeds.
    • In the case of flashing angles and waterstop angles, PVC should not be used and aluminium should be used wherever possible.
    • Surface priming for CFC, concrete, mortar screeds and plywood substrates should always be carried out with the manufacturer’s specified primers.
    • Surface priming will reduce porosity, dusting, air entrapment (pin holing) and high residual moisture in the substrate which will cause blistering of the membrane after curing.

Substrate Moisture

  • The third major cause of waterproofing failures is residual moisture in the substrate causing adhesive failure or de-bonding of the membrane.
    • There is no area of construction more critical to understanding the moisture content of a substrate than in waterproofing.  It is critical for the Builders and the Waterproofing Contractor to test the concrete of mortar screed substrate before the application of waterproofing.
    • Every concrete slab and mortar screed should be accurately assessed for the moisture content before the application of the waterproofing products.

Wet-seal Franchisees have been given the tools and training to overcome the issues noted in this article.

  • Preparation – where Wet-seal demonstrate and inform you, the importance of preparing the job correctly – this actually ensures your job complies with all regulations and also speeds up the application of the waterproofing membrane.  An uneven surface can take at minimum twice as long to waterproof.
  • Moisture in the substrates has and will continue to cause failures in the field in relation to waterproof membranes, that’s why Wet-seal demonstrate the importance of using the moisture meter instead of finding out years later that the moisture content has effected the membrane regardless of the membrane used, as all are effected by moisture in the substrate at the time of membrane application.

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 0800 436 000 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

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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