Water Ingress to Balcony Suspended Slabs

Balcony Suspended slabs

Suspended balcony slabs are integral to both residential and commercial construction, offering a flexible and efficient structural solution. In residential settings, they are frequently utilised in multi-story buildings and large high-end homes with spacious outdoor balconies. However, suspended balcony slabs exposed to the harsh outside conditions all year round can be challenging to achieve adequate long-term waterproofing. Items such as poor / blocked drainage, inadequate falls and garden beds typically being the most problematic.

Common Defects Related to Water Ingress:

Common defects associated with water ingress that you may notice on your suspended balcony slab are as follows:

  • Efflorescence – White staining on concrete, indicating salt deposits.
  • Rust stains – A consequence of steel corrosion within the suspended concrete slab.
  • Concrete cancer or spalling – Deterioration or flaking of the suspended concrete slab.
  • The growth of mould and algae, posing aesthetic and structural concerns.

Common Rectification Methods to Address Water Ingress:

Common rectification methods for addressing water-related issues on suspended balconies involve a long-term approach which can be iterative, whereby the most likely causes and rectification strategies would be considered first. With the understanding that other additional rectifications would be likely, and subject to ongoing monitoring and the success of any previous measures taken.

Common rectification methods are as follows:

  • Implementing positive / negative waterproofing of slabs to mitigate water penetration.
  • Crack injection is employed to address and seal structural cracks.
  • Additional drainage solutions, such as grated drains, perimeter drains, and sump drains.
  • Removing garden beds contribute to minimising water retention around the structure.
  • Re-profiling or topping of slabs is undertaken to achieve proper falls for water drainage.
  • Repairing and upgrading plumbing systems.


See our ‘case study – project assistance for a repair on an existing penthouse balcony – West End, Brisbane’ article for a more detailed write up on this project.

Balcony Suspended slabs

For expert guidance and assessment of your suspended balcony slabs, we recommend reaching out to Booth Engineers and Associates Pty Ltd.

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For more information, or to get a quote , please contact our team.