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Edition 3 – Drainage & Waterproofing

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.
  • Water migrates through grout and builds up over the membrane within the screed.  When there is inadequate fall to the waste outlet, this tends to lead to salt calcification/efflorescence.  This can be avoided by ensuring there is fall to the outlet and good 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.

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