Measuring Wood Moisture with Wood Moisture Meters

In general, a wood moisture meter cannot be used on walls. There are combination meters that include material characteristics for both wood and mineral building materials. Meters designed exclusively for wood are calibrated for the electrical properties of wood and therefore often provide unreliable or difficult-to-interpret readings when used on masonry.

The term “resolution” is often confused with or equated to accuracy. This is incorrect. High resolution does not automatically mean high accuracy. The accuracy of a wood moisture meter depends heavily on its design and quality. Professional devices, such as those from GANN, are equipped with a high-quality measurement amplifier and achieve accuracies of ±0.5 percentage points (Hydrometten) and ±1 percentage points (compact-class Hydrometten), depending on the measurement range. These devices thus deliver very precise results - even in the low wood moisture range, which is critical in the furniture and construction industries. Inexpensive devices from home improvement stores, on the other hand, often exhibit significant deviations and are better suited for rough estimates. In addition to the device’s technology, proper use plays a crucial role in obtaining accurate measurement results: The wood species must be set correctly, the temperature must be taken into account, and the measurement must be taken at a suitable location. In particular, measurements taken at the end grain, in cracks, or on unsplit surfaces can easily lead to inaccurate results.

A wood moisture meter measures the absolute moisture content of the wood, expressed as a percentage by weight. This value indicates how much water the wood contains relative to its completely dry state. Most handheld meters operate by measuring the electrical resistance between two metal pins: The wetter the wood is, the better it conducts electricity, and the lower the measured resistance. Some devices use a capacitive method instead of resistance measurement, in which moisture is determined via an electric field without piercing the wood. For reliable results, firewood should always be measured on a freshly split inner surface, since the outer bark is often significantly drier and yields inaccurate readings.

A wood moisture meter works by measuring either the electrical resistance or the dielectric properties of the wood. Devices with measuring probes pass an electric current between two electrodes that are driven into the wood. Since drier wood has higher electrical resistance and moister wood conducts electricity better, the device can calculate the moisture content based on this. Capacitive meters generate an electromagnetic field and measure how it changes due to the moisture in the material - without damaging the wood at all. Both methods require the correct wood species setting, because different wood species conduct electricity to varying degrees, and failing to set this correctly can result in inaccurate readings. For years, GANN has been known for manufacturing high-quality wood moisture meters. GANN’s Hydromette BL A plus now combines the high-precision resistance measurement method with the non-destructive capacitive measurement method in a single compact device.

A wood moisture meter is used to reliably determine the actual moisture content of wood. This value is crucial for assessing whether firewood will burn cleanly and with low emissions, whether timber is suitable for processing, or whether wood used for furniture is sufficiently dry to prevent cracking or warping. The device thus enables a reliable assessment of wood quality before and during processing and helps prevent damage, energy loss, or malfunctions when using a fireplace. When heating, knowing the moisture content is important because wood that is too wet burns less efficiently and produces higher emissions.

To use a wood moisture meter, first set the correct wood species group on the device. If the device has a wood temperature compensation feature, set that as well. Then press the measuring pins into the wood at a right angle to the grain. When measuring the moisture content of firewood, it is best to use freshly split wood to access the moister core. Since moisture levels can vary within a single piece of wood, it is advisable to take several measurements at different points and then calculate an average value. For use as firewood, the moisture content should be below 20 percent; an optimal residual moisture content is approximately 15 to 18 percent.

The choice of a wood moisture meter depends primarily on the intended use and the required accuracy. For firewood, a simple pin type meter is usually sufficient, as long as it reliably indicates whether the moisture content is below the often-recommended threshold of 20 percent. For professional use in timber construction or the furniture industry, however, high-quality meters with the appropriate accessories are necessary. That’s why GANN’s product portfolio includes a wide range of accessories for every application - from measuring firewood to determining the moisture content in sawn timber with a thickness of 20 mm or more, to measuring beams with a thickness of up to 180 mm. On the other hand, those who wish to test sensitive surfaces or veneers should choose a capacitive moisture meter, which operates in a completely non-destructive manner. Also important are material characteristics for different wood species, a sufficiently large measurement range, good resolution, and - for more demanding applications - temperature compensation, as this significantly improves accuracy.

A sturdy, probe-type wood moisture meter is particularly well-suited for firewood. Ideally, the wood should be freshly split before measurement, as this allows the moisture content to be determined directly at the core of the log, thereby providing the most accurate results. The probes should be able to penetrate as deeply as possible to measure the actual residual moisture content, which is crucial for clean and efficient combustion. A good meter measures in the range of 10 to 50 percent and ideally offers a wood type setting so that different types of wood can be accurately assessed. Models from GANN offer particularly reliable measurement quality and are therefore recommended for both private fireplace owners and professional users.