Hello, this device will measure moisture between 0.8 to 1.6" in depth. Depending on the thickness of the plaster and wood, the Moisture Meter could measure a single material or both. The device will display relative moisture readings between 0 and 100%. The "RISK" alarm will go off at 30% by default, and the "WET" alarm will go off at 60% by default (though these alarms are user adjustable). The presence of metal could interfere with the Moisture Meter's electromagnetic sensor and provide unreliable measurements.
This device can detect the moisture of gypsum/cement/wood between 0.8" to 1.6" of depth, regardless if there is vinyl flooring in the way. If you have any further questions, feel free to email us: info@reedinstruments.com