New Zealand Flooring Standards require concrete floors to have a relative humidity level of no more than 75 % before floor coverings can be installed.

Simple non-invasive "scanning" capacitance meters either do not provide a humidity RH reading OR are simply not an accurate method of "measuring" concrete moisture. *More information can be found by referring to the NZ Flooring Industry Standards AS/NZS 2455 and AS/NZS 1884 and BRANZ Bulletin and 585..

The only way to perform a humidity measurement is with a Hygrometer. The T260C is a hygrometer.

For a non destructive method of measuring, the hygrometer can be used with a humidity box. This box (with a small cavity on the underneath side, and a plugged hole in the side) is sealed to the top of the concrete slab and left, typically, for a period of 24-36 hours. Because the cavity space on the underneth of box is less dense than the concrete, the movement of moisture occurs from the concrete into this space. After the alotted time period, the plug from the side is removed and the hygrometer is inserted into this hole to measure the RH inside the cavity within the humidity box (see Image 1 left). Often 2 or 3 boxes are used across a whole slab. The average reading is then taken.

For an invasive deeper method of measuring, holes can be drilled into the concrete and plastic sleeves can be inserted into the slab. The sleeve, approx. 16mm in diameter, is inserted into the drilled hole, then capped and left, typically for a period of 24-36 hours. Several sleeves are inserted into the concrete to attain areas over a greater area on the concrete slab when compared to the humidity box option above. Because the sleeve is perforated and the space inside the sleeve is less dense than the surrounding concrete, the movement of moisture occurs from the concrete into this space. After the alotted time period, the cap is removed and the hygrometer is inserted into this sleeve to measure the RH within the concrete slab (see Image 2 left).

A wide range of accessories including humidity sleeves, humidity boxes, soft and hard carry cases are available for the T210C.