What changed in the 2021 edition?
| Test | Status in AS 1884:2021 |
|---|---|
| In situ relative humidity probe, ASTM F2170 | The only normative test |
| Hood test, ASTM F2420 | Withdrawn, no longer accepted |
| Anhydrous calcium chloride, ASTM F1869 | Informative, for a slab that cannot be drilled or where the maker asks for it |
ASTM F2170 now needs 24 hours from when the sleeves go into the holes, where the earlier version needed 72. So a test is a two visit job: drill and set the probes, then read them a day later.
Carpet runs to a different standard. AS 2455, revised in 2019, dropped the capacitance meter and lists the invasive hygrometer and the hood test as informative methods.
Why do store slabs fail?
Western Australia's Department of Housing and Works, which had slabs fail the 2021 test on several projects, lists the patterns it sees:
- High readings in patches, where a trench was cut for services and filled with new concrete that has not dried
- Slabs older than about 30 years that read high everywhere
- Mostly dry slabs with wet readings around the perimeter
The first one is the store pattern. Trenches cut for checkouts, refrigerated cases and power to island displays are filled with fresh concrete, and a new floor laid over them on the refit timetable is laid over a wet patch.
The same guideline puts most moisture related floor failures down to testing that was missing or done the wrong way.
What happens when a slab fails?
The slab can be left to dry and tested again, or a moisture barrier system can go down before the floor. A barrier is a set of products that have to work together: a polymeric membrane, a levelling compound over it, the adhesive and the floor covering.
WA's guideline shows what a strict owner asks for. Its non residential buildings now get a barrier on every slab under resilient flooring, whatever the reading. Readings over 90% stop the job for investigation. The membrane goes on in two coats in crossed directions, the levelling compound is nominally at least 2 mm thick, and the installer and maker give one 10 year warranty over the whole system. AS 1884 does not ask for any of this, but it is a useful benchmark for a retailer writing its own specification.
Who sets the pass level?
AS 1884 sets the minimum. The flooring, adhesive and levelling compound makers set their own limits in their installation guides and data sheets, and where theirs is stricter, theirs decides whether the warranty holds. Get the test results in writing, against the limit for the products actually being laid.
Replacing floors across a store fleet
- Make the moisture test a hold point in every store's scope: no floor ordered until the result is in writing
- Carry a barrier as a priced option per store, used only where the test fails
- Test infilled trenches separately from the main slab
- Set the slip rating for each area at the same time as the product
Nextage replaces commercial floors across store fleets, priced per site and scheduled around trading.
