Acceptable Moisture Level in Wood: MC Chart by Use (6-19%)

Acceptable moisture content in wood depends on where it will be used: about 6-10% for indoor furniture, flooring and trim, 9-14% outdoors, and no more than 19% for framing lumber. Install wood wetter than it will end up in service and it shrinks, cups or opens joints as it dries. This guide gives the chart by use, the humidity that sets each target, and how to measure with a moisture content calculator or a meter.

What’s An Acceptable Moisture Level For Wood?

The short answer is the moisture level the wood will settle at in its final home. The USDA Forest Products Laboratory puts it plainly in the Wood Handbook: install wood at the moisture content it will see in service, which keeps seasonal swelling and shrinking small after installation.

Install wood at the moisture content levels that the wood will experience in service.

USDA Forest Products Laboratory, Wood Handbook, Chapter 13

That is why a single number is misleading. The figure you will see most often, 6-8%, is a reasonable target for furniture and cabinets in a heated home. The Wood Handbook lists 8% as the average for interior woodwork, flooring, furniture and trim across most of the United States, with individual boards acceptable from 6% to 10%. It drops to a 6% average (4-9% per piece) in the dry Southwest and rises to 11% (8-13%) in damp, warm coastal areas. A cabinet shop in Phoenix and one in coastal Georgia should not be drying to the same number.

Two common claims on other sites do not hold up. Neither the claim that wood over 8% invites rot nor the claim that wood under 6% turns brittle appears in the Wood Handbook; its decay warning is about extended storage above 20%. And construction lumber is not left wetter "for flexibility": the 19% cap exists to limit shrinkage and decay, not to help shaping.

Wood Moisture Content Chart: Acceptable Levels by Application

Use this chart as a quick reference. Numbers come from the Forest Products Laboratory Wood Handbook (Table 13-2 and the surrounding text) and a University of Maryland Extension firewood study.

Application	Target MC	What the source says
Furniture, cabinets, flooring, trim (most of the US)	8% average, 6-10% per piece	Wood Handbook Table 13-2, interior use
Same, dry Southwest	6% average, 4-9% per piece	Lower indoor humidity pulls wood drier
Same, damp warm coastal areas	11% average, 8-13% per piece	Higher indoor humidity holds more water in wood
Exterior siding, trim, sheathing	12% average, 9-14% per piece	Wood Handbook Table 13-2, exterior use
Softwood framing lumber	15% average target, 19% maximum	"Dry" lumber is 19% max; KD 15 stock is graded at 15% max
Heavy plank flooring	About 12%	Lets boards approach equilibrium with few gaps
Firewood	Under 20% (measured inside a split face)	University of Maryland Extension
Freshly cut (green) wood	Above about 30%	Fiber saturation point averages about 30%

Why furniture and flooring are kiln dried a little low. The Wood Handbook notes that producers often dry flooring and furniture stock slightly below service conditions, expecting a small gain in moisture during processing, shipping and installation. If you buy kiln-dried boards, a reading of 6-8% is normal and not a defect. For flooring specifically, our guide to acclimating hardwood flooring covers how long boards need to sit before install.

Why Humidity Decides the Right Number (EMC Table)

Wood trades moisture with the air until it reaches equilibrium moisture content (EMC), which depends mainly on relative humidity. So the target for a room is set by the air in that room. Here is the Forest Products Laboratory table for 70°F air:

Relative humidity	Wood settles at (EMC)	Typical place
20%	4.5%	Very dry heated room in winter
30%	6.2%	Heated home in cold, dry weather
40%	7.7%	Comfortable indoor air
50%	9.2%	Average indoor air
60%	11.0%	Humid summer indoors
70%	13.1%	Unconditioned room, damp season
80%	16.0%	Damp basement or closed shed
90%	20.5%	Near-saturated air

Read it as a diagnosis tool. A board that measures 12% and sits in a 40% humidity room will keep losing water until it nears 7.7%, and it will shrink as it does. A garage at 80% humidity will push even kiln-dried boards toward 16%. Our guide to the 30-50% humidity rule covers how to hold a room in the range that keeps wood stable.

Fiber saturation is about 30% MC. Wood only shrinks and swells below that point, and moisture meters are reliable only below it. Source: USDA Forest Products Laboratory, Wood Handbook Chapter 4

How To Measure Moisture Content In Wood

Moisture content is the weight of water in a piece of wood as a percentage of its oven-dry weight, so a very wet board can read well over 100%. There are two practical ways to measure it.

Using Moisture Meter Pins

A pin (resistance) meter drives two electrodes into the wood and reads how easily current passes between them. Wood conducts better as it gets wetter, which is why the reading works. Per the Wood Handbook, resistance meters measure reliably from about 6% to 30%; readings above 30% are only qualitative. Three habits improve accuracy:

• Apply the species correction from the meter manual, since different woods conduct differently at the same MC.
• Correct for temperature: the Wood Handbook gives roughly 0.5% for every 10°F the wood differs from the meter’s calibration temperature (add for colder wood, subtract for warmer).
• Drive the pins to one-fifth to one-quarter of the board thickness when the board is wetter inside than outside, so the reading reflects the average and not just the surface.

Non-Damaging Pinless Meters

Pinless (dielectric) meters press flat against the wood and read electrical properties through the surface, so there is no hole. The Wood Handbook says their signal is dominated by the surface layers, so a pinless reading may not represent the core if the board is wetter inside, and newer models need a density (specific gravity) setting. Their range is about 4% to 30%.

	Pin meter	Pinless meter
Leaves holes	Yes, two small ones	No
Reads	Between the pin tips (can reach the core)	Mostly the surface layers
Reliable range (Wood Handbook)	About 6-30%	About 4-30%
Best use	Rough lumber, firewood, checking the core	Finished floors, furniture, scanning many boards fast

For most woodworkers, a pin meter is the better first purchase, and it is the type in the pick above. Buy a pinless meter later if you scan finished surfaces you cannot mark. Neither type replaces reading the manual for your species.

Other Methods Of Measuring Wood Moisture

The reference method is oven-drying. Cut a clean 1-inch cross-section at least 20 inches from the board end, weigh it, dry it at 101-105°C (214-221°F) until the weight stops changing, and compare. The Wood Handbook says a 1-inch section takes 12 to 48 hours. It is slow and destroys the sample, but it needs no meter. If you have no meter at all, see our guide on checking moisture content without a meter.

To avoid being fooled by one board, the Wood Handbook advises testing at least 10% of a lot, and the lot average should land within 1% of the target. In a house with 60 floor joists, that means at least six readings on joists picked at random.

How To Tell When Your wood is dry Enough To Use

Match the reading to the use. For framing, the American Softwood Lumber Standard defines dry lumber as 19% maximum, and framing is typically dried to a 15% average. Grade stamps help: KD 15 means the maximum is generally 15%. Common softwood dimension lumber is not usually dried down to the interior values in the chart.

Examples Of Dry Lumber

Kiln-dried lumber is the easy case, and it is safe to buy: kiln drying is a heat process, not a chemical treatment. Air-dried boards take longer and finish at whatever equilibrium your climate allows (see the EMC table above). For exact timing by species, see our guide on how long wood takes to dry, and if a board is too wet, these methods to draw moisture out of wood help.

Firewood: The 20% Rule

For firewood, the target is under 20%, and where you measure matters. University of Maryland Extension advises splitting a piece and reading the middle of the split face, because the ends dry first and read low. In its study, hickory cut into unsplit 16-18 inch lengths and left uncovered was still above 30% after a year, while split pieces dried to about 20% in 6 months. It also found that wet wood costs you heat, since energy goes to boiling off the water, and produces more smoke and soot in the stovepipe. If a seller says wood is seasoned, test a split piece before the truck unloads. For one species in detail, see how long oak takes to season.

Framing and Construction Timing

The Wood Handbook offers a practical rule for new houses: if framing lumber is within about 5% of the moisture content it will reach in service when wall and ceiling finish goes on, there will be little or no shrinkage damage. It suggests checking door and window headers and joists with a meter, and installing interior finish and trim once they average about 12%. Waiting around 30 days in warm, dry weather after the house is roofed usually gets the frame there. In heated houses in cold climates, joists and studs can eventually drop to 6-7%.

Preventing Excess Moisture In Wood

Wood that sits above 20% for long periods can develop decay, so storage and handling matter as much as the number on the meter.

Proper Storage And Handling

The Wood Handbook recommends lifting bundled lumber at least 6 inches (150 mm) off the ground and covering it with plastic tarps so it does not take up rain or ground water. Never lay boards on concrete or soil. For stacking, spacing and airflow in a garage, follow our guide to storing wood in a garage.

Control Humidity, Not Just the Wood

Since indoor humidity sets the final moisture content, a dehumidifier or a vented crawl space does more than wrapping boards in plastic. Wood installed over a damp basement or crawl space can run above the interior values in the chart. Moisture barriers protect from liquid water, but they will not rescue wood in a room that sits at 70% humidity.

Regular Inspection

Re-check the meter on stored lumber every few weeks in humid seasons, and look for softening, discoloration or musty smell. Keep a note of readings by date so you can see a trend and not a single number.

Frequently Asked Questions On What Moisture Level Is Acceptable In Wood

What Is A High Moisture Reading For Wood?

For interior wood, anything above about 10% is high for most of the United States, because indoor wood settles around 8%. For framing lumber, above 19% is not "dry" by the American Softwood Lumber Standard. Sustained readings above 20% put wood at risk of decay.

What Moisture Level For Mold In Wood?

The Forest Products Laboratory does not publish a single mold threshold, but it warns that wood kept above 20% for extended periods can develop decay. Keep stored lumber under 19%, ventilated and off the ground, and treat any lumber that stays damp and musty as suspect no matter what the meter says.

Is 10% Moisture In Wood Bad?

It depends on the use. At 10%, wood is fine for exterior work and acceptable for interior pieces in humid regions, since the Wood Handbook allows up to 10% for individual interior boards in most areas. For furniture or flooring in a dry heated home, 10% will shrink toward 6-8%, so let it dry first.

What Should Be Maximum Moisture In Wood?

It depends on the job. Framing lumber is capped at 19% to count as dry, and KD 15 stock at 15%. Interior woodwork, flooring and furniture should be at most about 10% per piece in most US areas, exterior trim at 14%, and firewood should be under 20%.

Can Wood Be Too Dry?

Yes, relative to where it will live. Wood dried well below its in-service moisture content will take up water and swell after installation. That is why flooring and furniture stock is dried slightly low on purpose, but not far below the room’s equilibrium level.

Conclusion

Acceptable moisture content is not one number: it is the equilibrium level of the room or climate where the wood will live, usually 6-10% indoors, 9-14% outdoors, and 19% at most for framing. Measure with a meter, test several boards, and let the wood reach the target before you build. For more wood-care basics, see our woodworking tips and fixes guide.