Boosting Lumber Mill Profits with Moisture Measurement

Written by Wagner Meters, published first by Canadian Forest Industries (Nov./Dec. 2014)

Hardwoods of Michigan, Inc. (HMI), headquartered in Clinton, Michigan, has developed and maintained a lumber quality control program that focuses on moisture content. As a result, it has improved process efficiency, maximized output, and, most important, improved profits.

Over the years, this 100-person operation has expanded its facilities to include a sawmill, a drying complex, and a planing/ripping line. At the time this article was written in 2014, its kiln capacity was 700,000 board feet, its pre-dryer capacity was 1.5 million board feet, and its monthly drying output was 1.5 to 1.8 million board feet. The mill processes hardwoods including red and white oak, ash, hickory, maple, and cherry.

Drying Operations

The drying complex at HMI Hardwoods includes seven kilns. It typically takes four hours to unload and reload a kiln, and other than that downtime, the kilns run around the clock.

Unlike some mills, HMI doesn’t air-dry its lumber at all, because air drying requires more inventory and offers no climate control. Seasonal swings in temperature, humidity, and wind can cause air-dried lumber to degrade by 10% or more.

Air drying also doesn’t dry lumber evenly. By contrast, normal degrade in the pre-dryer is 3% or less. That difference in yield (10% vs. 3%) improves the mill’s profitability.

One more reason to pre-dry instead of air-dry: in Michigan, lumber can only be left outside for about six months of the year.

Pre-Kiln Operations

Stickers are placed in newly arrived green lumber, and the lumber is sorted by species and thickness and arranged into 80,000-board-foot bays. Next, the bays are loaded into one of two pre-dryers, which monitor temperature, humidity, and moisture around the clock.

• Stain-prone species such as maple go into a specially designed pre-dryer with air velocities of 300 to 500 feet per minute and operating temperatures of 100°F to 140°F, according to Randy Rickmon, HMI’s Pre-Dryer Manager. Typically, the process takes 10 to 12 days.
• Check-prone species such as oak go into a second pre-dryer with air velocities of 100 to 125 feet per minute and operating temperatures of 80°F to 90°F. Oak takes longer, typically 45 to 47 days.

For example, whitewoods spend about 9 days in the pre-dryer, followed by 4 days in the kiln. Red oak takes much longer: about 36 days in the pre-dryer, followed by 12 days in the kiln.

Quality Control in the Kiln

After pre-drying, HMI personnel move the charges of lumber into the kiln. They do quality and moisture checks at this point and prepare two sets of randomly assigned sample boards.

The first set, usually about 16 boards, is used to schedule and run the kiln. These samples come from the roughly 12,000 boards that make up the kiln charge.

The second set is used after kiln drying to evaluate moisture distribution and drying degrade.

Moisture Meters: The Key to Quality Control After the Kiln

After the lumber comes out of the kilns, 100 boards from each 80,000-board-foot bay are randomly tagged and sent to HMI’s quality lab for further evaluation.

After the boards are surfaced, employees scan each one with a Wagner L601-3 handheld moisture meter*. They record each board’s moisture content and inspect it for drying defects such as splitting, warping, checking, staining, and sticker marks.

Each board is then rated on a scale of 0 to 4, with 4 being a perfect score for a defect-free board. A report then summarizes the moisture distribution and overall drying quality.

HMI surfaces most of its production. Because of the mill’s layout, and unlike many mills, it planes the lumber right after kiln drying and checks moisture content after that.

After surfacing, each board passes over a Wagner in-line moisture meter. The target MC is 7%, so any board at 10% or higher is spray-marked and pulled from the sorting line for reprocessing.

*The L601-3 is no longer available. Wagner’s current industrial handheld meter is the L5300.

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Screening out lumber with high moisture content lets HMI:

• Assure customers of high-quality lumber and protect them from the problems that moisture content that’s too high can cause
• Find and remove the occasional wet board more easily, instead of extending kiln time and risking overdrying the rest of the charge
• Maximize production while saving 10% to 20% in costs compared with not scanning for moisture content, according to HMI

The Role of Moisture Meters on Untagged Lumber

Untagged lumber goes through Wagner’s in-line meter and scanner, which records each board.

Kiln size affects moisture content variability: the bigger the kiln, the more variation there is in the lumber’s MC. Wagner’s in-line meter helps HMI catch boards that are too wet or too dry.

Either way, employees pull that lumber from the line for reprocessing. The in-line meters outside the kiln help reduce the risk of shipping wet or overdried lumber.

Without these meters, HMI would be more likely to produce lower-quality lumber with high moisture content and lose money in the process.

Bottom Line: Moisture Measurement Determines Profitability

Quality control affects production yield and profitability. A quality control program has many parts, but moisture content, if it’s addressed throughout the entire production process, can have a big effect on your output and your profits.

A quality control program that focuses on moisture measurement and analysis before, during, and after kiln drying can significantly improve your results.

Wagner Meters’ in-kiln, in-line, and handheld meters can help you determine the true moisture content of your lumber. By making moisture meters part of its quality control program, HMI Hardwoods has increased its profits. What could better moisture measurement do for your mill?

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Larry Loffer

Larry Loffer is a senior technician at Wagner Meters, where he has over 30 years of experience in wood moisture measurement. With a degree in Computer Systems, Larry is involved in both hardware and software development of wood moisture measurement solutions.

Last updated on October 9th, 2026