Vapour barrier installation requirements

Manufacturers, suppliers and installers need to be mindful of the requirements for vapour barrier products, if sold or installed in Queensland.

Vapour barriers are also commonly known as:

  • builder’s film
  • slab underlay
  • builder’s plastic
  • waterproof membrane (200um WPM)

A vapour barrier must be installed under concrete slabs for:

  • slab-on-ground construction of any dwelling (class 1)
  • any class 10 buildings such as garages, carports, patios and the like, where the slab is continuous with the dwelling slab.

Some commercial buildings also require a vapour barrier to be installed.

Unless the vapour barrier is manufactured to meet Australian Standards and installed correctly, issues such as rising damp and/or mould may occur.

In Queensland, a vapour barrier must meet three specific criteria for compliance, otherwise it may not be suitable for use. It must be:

  • 0.2mm thick polyethylene film
  • medium impact resistant, as determined by Australian Standard 2870
  • branded continuously “AS 2870 Concrete underlay, 0.2mm Medium impact resistance”.

The QBCC advises the public and industry that plastic film offered for sale as builder’s film, whether through an online retailer or otherwise, must meet all three criteria if the intended use is as a vapour barrier or it may be considered as a non-conforming building product.

Under Queensland’s non-conforming building products law, every member of the construction industry supply chain, including manufacturers, distributors and installers, must ensure the building products they manufacture, supply or install, are compliant or risk significant penalties. If a person in the chain of responsibility becomes aware of, or reasonably suspects, a non-conforming building product, they are obligated to notify the QBCC within 2 days.

If you are an owner builder, licensed builder or concreter who is thinking of preparing a concrete slab that requires a vapour barrier, be sure to check that the product meets all three regulated criteria, before installation.