A moisture meter reading means nothing if the technique is wrong. Dealers who probe bark or end grain and quote those numbers are either misinformed or misrepresenting their product. Here's how to get a reading you can defend — and document.
The right tool
Use a pin-style moisture meter. For dealer use, invest in one with a calibration check function and a range that goes above 40% — you need to see exactly how wet problem batches are, not just know they're "out of range." Models in the $40–$80 range aimed at the building trades work well for firewood.
Calibrate your meter periodically. Most meters come with a calibration reference block, or you can use oven-dried wood (dried to constant mass at 220°F) as a zero-moisture check.
Where to probe — and where not to
Always probe freshly split interior surface
Split a piece and immediately probe the exposed interior face — not the bark, not the cut end. Bark and end grain dry faster than the interior and will consistently read lower than the actual moisture content of the wood. The interior of a freshly split piece gives the most accurate picture of what the wood will do when burned.
Probe perpendicular to the grain
Drive the pins across the grain, not along it. Along-grain readings track moisture channels in the wood and give artificially high numbers. Perpendicular to the grain is the standard method used by the forest products industry.
Probe at mid-depth
For large splits, the outer inch or two will have dried faster than the core. If your meter allows depth adjustment (some do via longer electrode pins), probe at a depth that represents the interior of the piece, not just the surface.
Sample correctly
One reading from one piece tells you almost nothing. To characterize a batch:
- Sample at least 10–15 pieces per cord
- Pull pieces from different positions in the pile — top, middle, bottom, interior
- Split each piece before probing — don't probe the surface of unsplit rounds
- Record the readings, not just the average
What you're looking for is a distribution. If most readings are 18–22% but a few are 30%+, you have a mixed batch. Don't average those outliers away — pull those pieces or disclose the variance to the customer.
Temperature effects
Cold wood reads artificially dry. In winter, wood stored outside can read 2–5% lower than its true moisture content because cold temperatures lower electrical conductivity. If you're measuring wood that's been in freezing temperatures, bring a sample indoors for 30–60 minutes and let it equalize before measuring.
Most quality meters have a temperature correction mode. Use it.
Document your readings
Date-stamped moisture readings tied to a specific batch protect you in disputes and build trust with customers. A simple approach: photograph your meter probe against a freshly split piece from a batch, with the reading visible. Store by batch date. Takes 30 seconds and creates a record you can share.
If you're listing moisture data on CT Firewood Delivery, that number needs to be defensible. A customer who buys based on your listed moisture reading and receives wet wood is a complaint — and a potential dispute. Accurate documentation protects both you and the customer.
Target numbers
- Under 20% — ready to sell as seasoned, will burn cleanly
- 20–25% — sellable as seasoned, disclose the reading
- 25%+ — do not sell as seasoned; it needs more time