Concrete Slab Moisture Testing Before Flooring: What the Australian Standards Say

Australian standards for resilient flooring and carpet point to an in-situ relative humidity probe test of the concrete slab as the preferred method. Surface tests can mislead. The hood test is still accepted in AS 1884 and AS 2455.1. We have not read the standards' text, so no humidity limit is quoted here.

The standards in play

• AS 1884 (resilient floor coverings). Supplier summaries say it warns that surface tests may not show whether a slab is dry enough, and prefers the in-situ probe test under ASTM F2170 where practical. One supplier says the only result it accepts is a relative humidity reading, taken with an in-situ probe or a surface-mounted insulated hood.
• AS 2455.1 and AS 2455.2 (carpet and carpet tiles). A 2019 update added in-situ RH probes as an accepted method for testing concrete subfloors, alongside the hood test.

These are summaries from suppliers who sell moisture-testing equipment. Buy or consult the current editions of the standards, and your flooring or adhesive maker's own limits, before relying on any figure.

The two methods

In-situ RH probe. Holes are drilled into the slab and a calibrated probe measures the humidity inside it. A testing service reports that adhesive manufacturers often ask for quantitative results from calibrated in-slab probes, not from handheld meters, which are only indicative.

Hood test. An insulated hood sits on the surface. One source says the ASTM group withdrew the hood test from its own standards in December 2014. It stays in the Australian standards, so it is still an accepted option here, but the probe is the method the standards favour.

Why it matters

A slab that is too damp can cause adhesives to fail, planks to lift and coatings to bubble. Resin coatings are a separate case: see why slab moisture matters before coating. For a coating, the maker's data sheet sets the limit, not AS 1884.

What to ask for

Ask for the test method, the number of test points, the reading and the date, in writing, and ask the flooring maker what reading they accept. This applies to hybrid, vinyl, carpet and timber floors over a slab: see hybrid vs vinyl plank vs laminate flooring and solid vs engineered timber flooring.

Find contractors

NSW Flooring lists businesses by service and region, from Google Maps, retrieved 22 October 2026. Examples for concrete work: polished concrete western sydney and polished concrete st george & sutherland, or browse polished concrete contractors in NSW. The listing does not say whether a business tests slab moisture, so ask. See how NSW Flooring sources its listings and polished concrete vs grind and seal.

Quick answers

Is a handheld meter enough? Suppliers say adhesive makers often want quantitative probe results, so a handheld reading may not satisfy a warranty.

What reading passes? We do not give one. It depends on the standard, the flooring and the adhesive. Ask the manufacturer.