How to Season Firewood and How Long It Takes
Seasoned firewood is wood dried to below 20% moisture content. Freshly cut wood is 35 to 50% water by weight, according to the CMHC wood-heating guide, and Utah State University Extension says green firewood may hold 50% or more. Every pound of that water has to boil off in the stove before the wood gives useful heat.
How long it takes
The sources agree on the target and differ on the time, because drying depends on species, piece size and weather:
| Source | Drying time |
|---|---|
| University of Maryland Extension | 6 to 9 months, split, stacked and covered |
| University of Kentucky Forestry | At least 6 months of air drying |
| CMHC guide | A full year or more; large hardwood pieces up to 2 years |
The safe plan is to buy or cut next winter's wood this spring.
What drying takes out
Utah State weighs cords green and dry. A cord of red oak drops from 4,888 lb green to 3,528 lb air-dried: 1,360 lb of water. A cord of sycamore loses 2,288 lb, and Kentucky lists sycamore's living-tree moisture at 114%, the wettest in its table. Species with low living-tree moisture, such as white ash at 45%, season sooner.
How to stack it
- Split first. Split wood dries much faster than rounds; University of Maryland Extension's times assume split, stacked wood.
- Cut to length. Maryland suggests pieces about 3 inches shorter than the firebox, usually 16 to 20 inches.
- Stack off the ground, cover the top, leave the sides open so wind carries the moisture away.
- Keep a few days' supply inside. The CMHC guide suggests a 2- to 3-day supply indoors so it is warm and dry when it goes in the stove.
Checking it
Weathered, checked ends are a hint, not a test. Split a piece and read the fresh face with a moisture meter; Maryland Extension stresses testing the inside, not the outside. Wet wood also builds creosote faster (chimney guide).
Sources
- CMHC, A Guide to Residential Wood Heating.
- University of Maryland Extension, FS-937.
- University of Kentucky Forestry, Comparison of Properties Affecting Firewood.
- Utah State University Extension Forestry, Wood Heating.
Questions
How long does firewood take to season?
University of Maryland Extension says 6 to 9 months for split, stacked, covered wood; Kentucky's forestry table says at least six months; the CMHC guide says a full year or more, and up to two years for large hardwood pieces.
What moisture content is seasoned firewood?
Below 20%. Fresh-cut wood is 35 to 50% water by weight (CMHC); Utah State says green firewood may contain 50% or more.