It is important to ascertain the moisture content of the substrate prior to applying a floor coating, as otherwise the rising moisture can cause irreparable damage to the finish.
One of the primary ways to measure a substrate’s Equilibrium Relative Humidity (ERH) and Moisture Content (%mc) value is to use a Humidity Sleeve. Follow these seven steps to get an accurate moisture reading using this method:
1. Drill 16mm (5/8”) diameter clearance holes to a nominal depth of 50mm (2”) at the required points of measurement.
2. Position a plastic membrane over the hole and push a humidity sleeve through the membrane and down into the hole. Ensure that the flange of the humidity sleeve is flush with the floor surface and that the humidity sleeve cap is firmly in position in order to make an airtight seal.
3. Leave for at least 24 hours to ensure that moisture equilibrium conditions are reached within the humidity sleeve. Switch off any accelerated drying apparatus that may be in use for at least four days before taking the final readings.
4. If using the GE Protimeter Hygromaster instrument, the ERH reading is made with the Hygrostick sensor that comes supplied with it. Hygrosticks are fitted with a soft conical sealing sleeve and it is important that the tip of the Hygrostick protrudes fully from the narrow end of the sealing sleeve.
5. Connect the Hygrostick to the GE Protimeter Hygromaster via the extension lead.
6. Remove the humidity sleeve cap and push the Hygrostick assembly into the humidity sleeve and twist to seal. Ideally, leave the Hygrostick in the hole for at least 30 minutes before taking the first reading.
7. Measure the %rh in the hole to get the ERH value of the floor slab.
Check back on the blog next week to learn about another moisture measuring method – the humidity box.
Note: The operating instruction of the instrument being used needs to be consulted for specific information and Flowcrete will not be responsible for any loss resulting from this guide.