MC (Moisture Content)
Moisture content is the weight of water in wood expressed as a percentage of the wood's oven-dry weight. MC is the single most important property affecting lumber's stability, strength, workability, and susceptibility to decay. It is measured with pin-type or pinless moisture meters and is the primary quality control metric in lumber drying.
In-Depth Explanation
Moisture content fundamentally controls wood's behavior in every application. As wood dries below the fiber saturation point (approximately 28-30 percent MC), it begins to shrink, harden, and gain strength. Wood in service continuously absorbs and releases moisture in response to ambient humidity, causing dimensional changes that must be accounted for in design and construction. The target MC for lumber depends on its intended use: construction framing is typically dried to 19 percent or less (S-DRY standard), hardwood for interior furniture and cabinetry to 6-8 percent, and exterior woodwork to 12-15 percent. The formula for MC is: (wet weight minus oven-dry weight) divided by oven-dry weight, times 100. In practice, moisture meters provide instant readings without the destructive oven-dry method. Pin-type meters measure electrical resistance between two probes driven into the wood, while pinless meters use electromagnetic signals to scan the wood non-destructively. Accurate MC measurement at every stage — from green through drying to end use — is essential for quality lumber and successful woodworking.
Usage Example
The flooring installer checked the moisture content of the subfloor and the hardwood flooring, confirming both were within 2 percent of each other before beginning installation.