The gypsum manufacturing process requires that the finished gypsum board be very dry in moisture content, hence the alternate name drywall. While there is no industry standard or regulatory source specifying this moisture level, it is generally thought that a level below or about 1% is appropriate.
Finished gypsum board can be subject to moisture pickup during manufacturing, delivery, handling and installation. This applies even to moisture-resistant board and fire-resistant board. This exposure can come from a variety of sources including improper storage, construction or design defects, water leaks from floods, pipes, rain or cleanup activities. Should the installed board experience water intrusion, mold can quickly grow on the board surface or throughout the board. This must be dealt with within 24-48 hours after exposure in order to prevent mold growth which may require board replacement. The board may look and feel dry to the touch but harbor mold growth behind the wall.
Finna Group has long supplied the Model SMART III RF flat plate on line moisture meters for the measurement and control of real time moisture content. The RF sensors can be mounted inside the last zone or two of the drying kiln in order to fine tune the finished board moisture content via 4-20ma output signal to a temperature controlling PLC. The finished board is then measured using the same model with a 4 in. x 36 in. RF sensor mounted between conveyor rollers after the drying kiln. For portable moisture meters, Models LGF: Gypsum Moisture Meter, LG: Drywall Moisture Meter, LP: Lumber & Plaster Moisture Meter and A8: All-Purpose Moisture Meter are ideal instruments for non-destructively detecting the presence of excessive moisture throughout the drywall/gypsum board and are employed to confirm moisture conditions prior to shipment to ensure quality control.