Wood Species - Moisture Content and Weight
The amount of bounded water in wood is determined by the relative humidity (RH) of the surrounding atmosphere. The water content changes slowly as the relative humidity of the surrounding air changes.
Typical density values for fresh green wood versus air-dried seasoned wood:
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Wood Species | Fresh Green Wood | Air-dried Seasoned Wood (20% moisture content per weight unit) | ||||
---|---|---|---|---|---|---|
Specific Gravity | Density (lb/ft3) | Weight per Cord (lb/cord) | Specific Gravity | Density (lb/ft3) | Weight per Cord (lb/cord) | |
Afromosia | 0.71 | 44 | ||||
Alder | 0.72 | 45 | 3604 | 0.45 | 28 | 2218 |
Applewood or wild apple | 0.66 - 0.83 | 41 - 52 | ||||
Ash, black | 52 | 34 | ||||
Ash, Oregon | 46 | 38 | ||||
Ash, white | 48 | 41 | ||||
Ash, green | 0.85 | 53 | 4237 | 0.64 | 40 | 3178 |
Aspen | 43 | 0.42 | 26 | |||
Baldcypress | ||||||
Balsa | 0.18 | 6.9 - 12.5 | ||||
Basswood | 42 | 26 | ||||
Bamboo | 0.30 - 0.40 | 19 - 25 | ||||
Beech, American | 54 | 45 | ||||
Birch, British | 57 | 0.67 | 44 | |||
Birch, Paper | 50 | 38 | ||||
Black Ash | 0.54 | 34 | ||||
Black locust | 0.93 | 58 | 4614 | 0.79 | 49 | 3952 |
Black walnut | 0.91 | 57 | 4579 | 0.61 | 38 | 3053 |
Boxwood / Buis | 59 - 69 | |||||
Buckeye, yellow | 23.9 | |||||
Bur oak | 0.99 | 62 | 4923 | 0.69 | 43 | 3475 |
Butternut | 25.2 | |||||
Cottonwood | 0.93 | 58 | 4620 | 0.45 | 28 | 2218 |
Cedar, Alaska | 36 | 31 | ||||
Cedar, Eastern Red | 37 | 0.37 | 33 | |||
Cedar, Northern White | 28 | 22 | ||||
Cedar, Southern White | 26 | 23 | ||||
Cedar, Western Red | 27 | 23 | ||||
Cherry, black | 45 | 35 | ||||
Cherry, wild red | 26.5 | |||||
Chestnut | 55 | 30 | ||||
Cocobolo | 68.6 | |||||
Coralwood | 68.6 | |||||
Corkwood | 12.9 | |||||
Cottonwood, Eastern | 49 | 28 | ||||
Cottonwood, Northern Black | 46 | 24 | ||||
Cypress, Southern | 51 | 0.51 | 32 | |||
Dogwood (flowering) | 49.7 | |||||
Douglas Fir, Coast Region | 38 | 0.53 | 33 | |||
Douglas Fir, Rocky Mountain Region | 35 | 30 | ||||
Ebony | 0.96 - 1.12 | 60 - 70 | ||||
Elm, American | 54 | 35 | ||||
Elm, Rock | 53 | 0.82 | 44 | |||
Elm, Slippery | 56 | 37 | ||||
Eucalyptus, Karri West Autralia | 51.8 | |||||
Eucalyptus, Mahogany New South Wales | 66 | |||||
Fir, Balsam | 45 | 25 | ||||
Fir, Commercial White | 46 | 27 | ||||
Greenheart, British Guiana | 66 - 77 | |||||
Grenadilla, Mpingo | 75 - 78 | |||||
Gum, black | 45 | 35 | ||||
Gum, red | 50 | 34 | ||||
Hackberry | 0.82 | 51 | 4039 | 0.59 | 37 | 2938 |
Hemlock, Eastern | 50 | 28 | ||||
Hemlock, Western | 41 | 29 | ||||
Hickory | 1.03 | 64 | 5107 | 0.77 | 48 | 3830 |
Hickory, pecan | 62 | 45 | ||||
Honeylocust | 0.93 | 58 | 4638 | 0.72 | 45 | 3590 |
Hornbeam | 47.6 | |||||
Iroko | 0.66 | 41 | ||||
Ironwood, black | 67 - 81 | |||||
Jacarandá, Brazilian rosewood | 53 | |||||
Larch | 48 | 0.59 | 37 | |||
Lignum Vitae | 1.28 - 1.38 | 80 - 86 | ||||
Locust, black | 58 | 48 | ||||
Magnolia, cucumber | 32.2 | |||||
Mahogany, Honduras | 0.54 | 34 | ||||
Mahogany, African | 0.50 - 0.85 | 31 - 53 | ||||
Maple, bigleaf | 47 | 34 | ||||
Maple, black | 54 | 0.75 | 40 | |||
Maple, red | 50 | 38 | ||||
Maple, silver | 45 | 33 | ||||
Maple, sugar | 56 | 44 | ||||
Maple, Soft | 0.80 | 50 | 3960 | 0.53 | 33 | 2640 |
Mpingo | 75 - 78 | |||||
Mulberry | 0.95 | 59 | 4710 | 0.71 | 44 | 3533 |
Oak, Red | 0.98 | 61 | 4886 | 0.67 | 42 | 3350 |
Oak, white | 63 | 47 | ||||
Osage orange | 1.03 | 64 | 5120 | 0.91 | 57 | 4552 |
Persimmon | 48.5 | |||||
Pine, Lodgepole | 39 | 29 | ||||
Pine, Northern White | 36 | 25 | ||||
Pine, Norway | 42 | 34 | ||||
Pine, Ponderosa | 45 | 28 | ||||
Pine, Southern Yellow | 52 - 53 | 36 - 41 | ||||
Pine, Sugar | 52 | 25 | ||||
Pine, Oregon | 0.53 | 33 | ||||
Pine, Parana | 0.56 | 35 | ||||
Pine, Canadian | 0.35 - 0.56 | 22 - 35 | ||||
Pine, Red | 0.37 - 0.66 | 23 - 41 | ||||
Poplar, Yellow | 38 | 28 | ||||
Post oak | 1.03 | 64 | 5086 | 0.72 | 45 | 3590 |
Pecan | 0.99 | 62 | 4937 | 0.72 | 45 | 3590 |
Redwood, American | 50 | 0.45 | 28 | |||
Redwood, European | 0.51 | 32 | ||||
Rosewood, Bolivian | 44.3 | |||||
Rosewood, East Indian | 48.7 | |||||
Satinwood, Ceylon | 64.4 | |||||
Sourwood | 37 | |||||
Spruce, Engelman | 39 | 23 | ||||
Spruce, Canadian | 34 | 0.45 | 28 | |||
Spruce, Sitka | 33 | 0.45 | 28 | |||
Sugar maple | 0.95 | 59 | 4746 | 0.67 | 42 | 3350 |
Sycamore | 1.01 | 63 | 5051 | 0.54 | 34 | 2755 |
Red elm | 0.79 | 49 | 3947 | 0.58 | 36 | 2870 |
Sweetgum | ||||||
Sycamore | ||||||
Tamarack | 47 | 37 | ||||
Teak | 0.63 - 0.72 | 39 - 45 | ||||
Tupelo | ||||||
Walnut, black | 58 | 38 | ||||
White cedar | 24 | 23 | ||||
White elm | 0.88 | 55 | 4362 | 0.54 | 34 | 2755 |
Willow | 0.87 | 54 | 4320 | 0.43 | 27 | 2160 |
- density of water 62.4 lb/ft3 (1000 kg/m3)
- 1 lb/ft3 = 16.018 kg/m3 = 0.016 g/cm3 = 0.00926 oz/in3 = 2.57 oz/gal (Imperial) = 2.139 oz/gal (U.S.) = 0.0005787 lb/in3 = 27 lb/yd3 = 0.161 lb/gal (Imperial) = 0.134 lb/gal (U.S) = 0.0121 ton/yd3
- water content in wood
- Softwood - woods that come from gymnosperms (mostly conifers plants)
- Hardwood - woods that come from angiosperms (flowering plants)
In green softwoods the moisture content of sapwood is usually greater than that of heartwood. In green hardwoods the difference in moisture content between heartwood and sapwood depends on the species. Variability of green moisture content exists even within individual boards cut from the same tree.
When wood is alive and fresh it consists primarily of water, i.e. most of the weight is actually water. Green wood is freshly sawn wood in which the cell walls are completely saturated with water. Additional water may reside in the lumina. The moisture content of green wood can range from less than 30% to more than 200% of dry wood weight.
- Sapwood - the actively conducting portion of the stem in which parenchyma cells are still alive and metabolically active
- Heartwood - the darker colored wood found to the interior of the sapwood
Moisture Content of Wood in Equilibrium with Relative Humidity and Temperature
- in Fahrenheit
- in Celsius
Example - Moisture Content in Wood - Summer vs. Winter
At a given location the typical summer condition inside a house is 25 oC temperature with 65% relative humidity. The typical winter condition in the same house is 18 oC temperature with 15% relative humidity.
From the chart above we can estimate the moisture content in the wood in the house at summer time to be 12%. The moisture content at winter time can be estimated to be 3-4%.
Wood changes dimensions with moisture - it swells when it gains moisture - and it shrinks when it loses moisture.
Typical wood shrinkage from green to ovendry moisture content is typical 3-8% in radial grain direction and 6-12% in tangential grain direction. Volumetric shrinkage is typical 11-18%. Longitudinal shrinkage parallel to the grain is generally quite small. Typical values from green to ovendry wood are 0.1-0.2%.
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