What seasoned firewood means, in numbers
Seasoned firewood has dried until its moisture content is under 20 percent, which the EPA’s Burn Wise program set as the figure for wood that burns well. Getting there takes at least six months of drying after the wood is split, and longer here.
Burn Wise, which the EPA ran from 2009 to 2025, put it in three lines: wood should be under 20 percent moisture, seasoned for at least six months, and checked with a moisture meter before it goes in. The Chimney Safety Institute of America’s homeowner page says the same thing in two words: well-seasoned only.
This matters to a chimney sweep because wet wood is one of the main reasons flues glaze over, and in the living room it passes for a draft fault: a fire that will not stay lit, or smoke rolling into the room while the kindling catches. A fire fed with 30 percent wood spends its heat boiling water, burns cool and smoky, and leaves creosote on the flue walls.
The chimney sweep page explains what we find in those flues, and the creosote stages guide shows what each degree looks like.
How to season wood in a wet climate
Split it early, stack it off the ground in single rows with only the top covered, and meter it before it burns, because Portland’s drying window is short and its wet season long.
- Get the wood early. Buy or cut it by early spring at the latest; the Oregon State University Extension forester quoted in the regional press advises having firewood a year ahead of when you burn it.
- Split it small and split it now. Wood dries from the split faces, not through the bark. A round left whole barely dries at all; a split the size of your forearm dries in months.
- Stack it off the ground. Pallets, rails or blocks keep the bottom row out of the mud and let air move under the pile.
- Single rows, in the sun and the wind. A long single row along a south or west fence dries far faster than a cube in the shade of the north wall. Leave a hand’s width between rows.
- Cover the top only. The EPA’s instruction is to store wood outdoors, off the ground, with only the top covered, because covering the sides traps moisture. A tarp wrapped to the ground makes a greenhouse for mold.
- Test before you burn. Split a piece, press the meter pins into the fresh inside face at room temperature, and read it. Under 20 percent goes in the house; anything higher goes back on the stack.
The Portland calendar for a woodpile
Portland’s drying season is July and August, the two months NOAA’s normals show with barely half an inch of rain each, and the wet season runs November through March, when about two thirds of the year’s rain falls.
That gives a plain schedule. Wood split and stacked by April has the spring breezes and the whole dry summer to lose its water, and can read dry by October when the first fires go in. Wood split in September has missed the window and should be treated as next year’s supply, however dry the bark looks.
Oak and the other dense hardwoods take longest, and the forester’s year-ahead rule is the safer one for them. If the pile is a mix, burn the fir and alder this winter and let the oak stand in the row for another summer.
How the local species burn
Firewood sold around Portland includes Douglas fir, red alder, bigleaf maple and, when you can find it, Oregon white oak, and each behaves differently in the firebox.
| Species | How it burns | Splitting and seasoning | Where it fits |
|---|---|---|---|
| Douglas fir | Medium heat, low ash, lights easily | Tight-grain older wood splits easily; young small-diameter rounds can be stubborn; dries within one dry season once split | The everyday fuel and the kindling |
| Red alder | Warm but fast when seasoned; wet alder gives little heat and a lot of ash | Cuts and splits easily; dries quickly once split | Shoulder-season fires, mixed with fir |
| Bigleaf maple | Close to ash in quality, a little cleaner, but it sparks more | Moderate to split; give it a full season | Longer evening fires, behind a screen |
| Oregon white oak | Hard to beat when fully seasoned; unseasoned, little heat and lots of ash | Dense and slow to dry; plan on a year or more | Long overnight loads in a stove |
Those ratings come from Steve Bowers, an Oregon State University Extension forester, as quoted in a 2014 regional column. He called Douglas fir a medium-heat, low-ash wood and one of his first choices, described seasoned alder as warm but fast, put maple close to ash with more sparks, and said properly seasoned oak is hard to beat.
His point about ash is a point about seasoning, not species. Wet alder and wet oak both leave a lot of ash and little heat; the same wood a year later behaves the way the table says.
Reading a moisture meter
A pin moisture meter is an inexpensive tool and the only honest way to know if wood is ready. The reading that counts is taken on a freshly split face, not on the weathered outside of the piece.
The outside of a split dries first and can read well under 20 percent while the core is still wet. Split the piece, push the pins into the middle of the new face along the grain, and take the reading with the wood at room temperature, since cold wood reads low. Check three or four pieces from different parts of the stack, not just the top row.
What not to burn, by the EPA and by Oregon law
Some things never go in a fireplace or stove: trash, painted or treated wood, plywood and particleboard, driftwood, and wood that is wet, rotten or moldy. The EPA’s list and Oregon’s statute overlap almost line for line.
Burn Wise names household trash including cardboard, plastics, foam and colored ink; coated, painted and pressure-treated wood; ocean driftwood, plywood, particle board and anything with glue in it; wet, rotted, diseased or moldy wood; and plastic, asbestos, rubber, manure and animal remains.
Oregon’s statute on solid fuel burning devices bars garbage, treated wood, plastic, rubber, animal carcasses, asphalt products, waste petroleum products, paint, chemicals, and paper beyond what it takes to light the fire. Treated and painted wood is the one that catches people out on a remodel: the offcuts go to the transfer station, not the stove.
Why wet wood is a chimney problem, not just a heating one
Wet wood makes creosote, and creosote is the fuel a chimney fire burns. Every pound of water in a split has to boil off before the wood burns, and the cooled, smoky exhaust condenses on the flue walls on the way out.
The trade’s rule is to sweep at an eighth of an inch of buildup, and a winter of damp alder in an open fireplace can get a flue there in one season. Dry wood makes less of it, not none, so the yearly inspection and the sweep when the buildup calls for it stay on the calendar; the how often to sweep guide works through the schedule.
The symptoms of wet wood look like draft problems: a fire that sulks and dies back, hissing, blackened glass on a stove, and smoke spilling out of the opening while the fire gets going. Before anyone opens the flue to look for a blockage, split a piece of the wood and put a meter on it.
Buying firewood: what to ask
Ask when the wood was split, not when it was cut; a log that lay in the woods for a year and was split last week is green wood.
Ask the species, because a cord of alder and a cord of oak are different purchases, and ask whether you can test a piece on delivery. Then do it: split one, meter the fresh face, and if it reads over 20 percent, stack it as next year’s wood rather than arguing. Wood sold as seasoned is a description, not a measurement.
One more Portland rule. On a red day in Multnomah County the county’s page says no burning is allowed unless an exemption applies, and on a yellow day it asks you to consider limiting burning; dry wood smokes less on every other day, which is the whole point of the pile. The wood burning rules guide covers the counties one by one.