Applicable Standards and Best Practices
The most prevalent standard in flooring installation is AS/NZS 1884, Floor Coverings-Resilient Sheet and Tiles- Installation. It was revised and re-published in June 2012. One of the biggest revisions was to the moisture testing regime for concrete sub floors. Moving away from capacitance and resistor "Moisture Content" (MC) tests it now specifies that Relative Humidity must be determined, using the in-situ probe method (ASTM F2170).
There were, originally, allowances for exceptions where drilling the slab is not possible, in which case the surface-mounted insulated hood method was advised (ASTM F2420). UPDATE: As of 2015 the INSULATED HOOD METHOD ASTM F2420 has been WITHDRAWN by the ASTM standards committee.
Another relevant standard is AS/NZS 2455, Textile Floor Coverings- Installation practice- also stipulates Relative Humidity and acknowledges that the "Moisture Meter" test is not applicable, other than to indicate the possibility of excess moisture and therefore the need for a full ASTM compliant RH test. The in-situ RH method, done in accordance with ASTM F2170 is the most accurate way of pinpointing the maximum potential RH which a floorcovering will experience at any future point. It is also the most efficient and cost-effective test to perform.
Textile floorcoverings such as carpets are becoming increasingly non-permeable. Even if the carpet does "breathe", the in-slab RH under textiles can lead to the formation of harmful bacteria and mould, much of which has been linked to serious ongoing medical conditions. Between this and the potential for flooring failure, correct testing is of paramount importance.
Manufacturers' Specifications
The AS/NZS Sandards give guidelines of best practices, and are vital to architects, builders, tradespeople and other stakeholders. Additionally, manufacturers of various flooring installation products are increasingly moving towards specifying in-situ RH% as per ASTM F2170 as part of their warranty requirements. It is in the best interests of manufacturers to incorporate the most up to date methods of quality control into their warranties, just as it is in the best interests of tradespeople and their employers to ensure these practices are followed.
Major government construction authorities are now specifying that moisture testing be undertaken as per the new standards and CONFIRMED prior to installtion.
A growing list of manufacturers specifying testing for RH using in-situ probes is available at www.rhspec.com. It also contains resources for manufacturers wishing to revise their specifications.