Moisture Content (MC)
The percentage of water in a wood product or subfloor, measured with a pin or pinless meter.
Moisture content is expressed as the percentage of water by weight in a wood product. Hardwood flooring is typically manufactured at 6-9% MC. Subfloor plywood should be within 2-4 percentage points of the flooring at install time.
Measure MC with a pin meter (penetrating, accurate) or a pinless meter (surface scan, faster). Take readings at multiple points across the room and on multiple boxes of flooring. Document each reading.
Out-of-spec MC at install time is the leading cause of hardwood callbacks. Wait for the readings to come into spec before installing — this is what acclimation is for. Documented MC readings are also your best defense if a manufacturer disputes a warranty claim.