The Revised Australian Standard for Resilient Flooring Installation AS1884-2021 – Moisture Barrier performance

Article by David Hood and Stephen Wood, ARDEX Australia

After a two year period of drafting and then revision starting in 2019, the revised version of AS1884-2012 was released as AS1884-2021. A review was called for by sponsor industry groups because a number of issues had arisen with the 2012 version, most notably concerning moisture testing of the subfloor, but also concerning performance criteria for sand-cement screeds and moisture suppression systems.

During the standards committee discussions it became clear that some minimum requirements were needed and moisture suppression via moisture barriers was considered an installation critical factor. Unlike in other jurisdictions, there was no measurable requirement for this property in our Australian market so discussion centred on determining one.

There are two main types of moisture barriers, sub-slab plastic sheeting compliant with AS 2870 and topical products (usually liquids) that are applied on to the concrete surface. The topically applied barriers have no Australian performance specifications, whereas in the US there are standard requirements (e.g., ASTM F3010 for certain types). Therefore, a decision was made to look into potential methodologies of test and appropriate testable pass-fail measures for these barriers.

Arguably, topically applied moisture barriers are a type of waterproof membrane as defined in the standard for waterproofing domestic wet areas AS 3740-2021. One suggestion was to examine the requirements in the related AS/ NZS 4858 which is the testing standard for waterproofing membranes. The difference here being that classic ‘membranes’ are intended to stop liquid water and water vapour from above, whereas for resilient flooring the moisture barrier has to be more effective for stopping water vapour from below.

The standard AS/NZS 4858-2004 carries a test criterion for water vapour resistance and uses the test method ASTM E96, which defines methods of measuring permeance and water vapour transmission rates. This standard method ASTM E96 has been around since the 1930s and is used widely for measuring the performance of moisture suppression of many materials, so it was a logical choice.

The committee decided to seek outside opinions and so several industry majors, all with expertise in this area of supplying moisture barriers, were polled by the lead author for their input. The consensus was that the selected figure of a water vapour transmission rate (WVTR) for topical moisture barriers of 10gm/m2/24hrs was acceptable in our market (whereas AS/NZS 4858 uses 8gm for this test).

The 10gm value is less conservative than the commonly quoted and strict values <0.1gm/ m2/24hrs in overseas (US, UK and European) markets for the widely used topical epoxy products. A WVTR requirement was also introduced in AS1884-2021 for concrete (<15gm/ m2/24hrs, which was based on the long standing de-facto US figure of 3lbs/10002ft/24hrs). The requirement for an emission rate was a consequence of the introduction of ASTM F1869 as the secondary moisture test method; a figure lower than 15gm would allow a factor of safety for less than adequate installation.

During the standard review period, some concern was raised about how ASTM E96 would be tested by installers in the field, but this was clarified by adding a statement that this requirement was a proof test for manufacturers of the products. This is no different to many other proof tests for materials in various standards and is a core feature of the concept of performance-based systems.

Conducting the proof testing via ASTM E96 requires adapting the methodology to suit the material undergoing the test, be it a film tested by itself or on a porous filter paper, applied on a standard porous ceramic base or simply a masonry substrate sample. The lead author has conducted ASTM E96 testing on a range of moisture barriers on such substrates and produced workable results.

In conclusion, there has been some confusion in the industry about this change, how to apply it, and what the motivation was. The answer is quite simple really, it places onus of proof of the product performance on suppliers, allows the consumers to compare systems based on hard data rather than anecdotal historicity and thus determine which barriers have the performance they require for their flooring projects.