Air-dried Lumber: Lumber that has reached its equilibrium moisture content by being exposed to air.

Board Foot: A unit of lumber measure that is 1” thick by 12” wide by 12” long. A board 1” by 6” by 2’ equals 1 board foot. A board 2” by 12” by 12” equals 2 board feet.

Boule: A log live sawn and kept together in the order of sawing.

Bow: A form of warp that is an end-to-end curve along the length of the board.

Burl: a wartlike growth that forms on a tree and that, when sliced, produces extremely disoriented grain patterns that are quite attractive.

Cant: A log that has been debarked and sawn square.

Case-hardening: A drying defect where the surface of wood dries faster than the wetter inner core; this causes permanent set and stresses that release when the board is cut.

Common: (mixed 1 and 2 common) are boards that have too many defects to be FAS or Select.

Conifer: A type of tree that’s characterized by needle-like or scale-like foliage, usually evergreen.

Crotch: The highly figured wood that occurs where a limb joins a trunk; the grain swirls dramatically where the wood fibers have crowded and twisted together.

Crook: A form of warp that is an end-to-end curve along the edge of the board.

Cup: A form of warp that is an edge-to-edge curve across the face of the board.

Deciduous: A type of tree where the leaves fall off every autumn; typically a hardwood, but not always. Some hardwoods in tropical regions keep their leaves all year long.

End checks: A drying defect caused by the ends of the boards drying faster than the rest of the wood; can usually be prevented by sealing the end grain.

End-coating: The process of sealing the ends of the boards to prevent checking caused by unrestrained evaporation of moisture.

FAS: First and Second. Mixed domestic hardwood lumber grade is the highest grade of hardwood lumber. In most species a board must be 6” or wider, 8’ or longer. Walnut and butternut are the exceptions.

Fiddleback: A type of washboard-like figure that occurs in some species of wood with wavy grain.

Figure: The pattern on a wood’s surface, resulting from the combination of its natural features and the way the log was cut.

Flitch matched or Book matched: Sequentially sawn lumber from the same log.

4/4, 5/4, 6/4, etc: Is the thickness given in fractions. It implies that the lumber is rough sawn 1/16”+ over the stated fraction.

4/4 = 1-1/16” to 1-1/8” and should finish to 13/16”
5/4 = 1-5/16” to 1-3/8” and should finish to 1-1/16”

Grade: A designation of the quality of a log or wood product such as lumber, veneer, or plywood.

Grain: The direction of wood fibers in a tree or piece of wood with the respect to the axis of the trunk.

Hardwood: Wood cut from the broad-leaved, mostly deciduous trees that belong to the botanical group Angiospermae.

Heartwood: Mature wood that forms the spine of the tree.

Honeycomb: A drying defect that occurs when the lumber undergoes severe case-hardening in the early stages of drying; appears as deep, internal checks.

Juvenile wood: The wood in every tree that forms within its first 10 years or so; usually has undesirable characteristics such as low strength and shrinkage along the grain.

Kiln: A heated chamber of a building used to dry lumber; humidity and air circulation are constantly monitored and adjusted as the wood dries.

Kiln-dried lumber: Lumber that has dried in a kiln to specific moisture content.

Knot: The section of a branch or limb that has been overgrown by expanding girth of a tree; may be loose or tight.

Moisture Content: The amount of water in a piece of wood expressed as a percentage of the green weight minus the dry weight times 100, divided by the green weight.

Nominal dimensions: Dimensions based on rough-cut(unplanned) softwoods; a 2×4 is nominally 2” x 4”—It’s actually 1-1/2” x 3-1/2”.

Pith: The small, soft core occurring in the center of the tree trunk. 

Plain Sawn: Lumber sawn parallel to the grain.

Quatersawn Lumber: Vertical grained lumber.

Ray: a ribbon-shaped strand of wood cells that extends from the inner bark to the pith perpendicular to the axis of a tree trunk; rays appear as fleck on quartersawn surfaces of some species.

Rift Lumber: Diagonally grained lumber.

Sapwood: New wood surrounding the denser heartwood.

Select: A clear board that is too short or narrow to be FAS.

Shake: A lumber defect that is a lengthwise separation of wood, usually along the growth rings.

SLR1E: Straight Line Rip One Edge

SLR2E: Straight Line Rip Two Edge

Softwood: Wood cut from coniferous trees belonging to the botanical group Gymnospermae.

Spalting: An attractive dark brown or black stain in some woods caused by decay.

Speck: A defect that’s caused by a fungus living in a tree, which appears as small white pits or spots.

Split: A separation of wood fibers that extends completely through a piece of lumber, usually at the ends.

Sticker: A piece of wood, typically _” square, that’s inserted at regular intervals between layers of green wood to assist the drying process.

Sticker Stain: Sometimes called shadow, it’s a stain that forms under the stickers in a stack of drying wood.

Stripe: A stripe or ribbon pattern that occurs when woods with interlocked grain (which slopes in alternate directions) are quartersawn.

Surfaced Checks: A drying defect that occurs when the surface dries too quickly in relation to the core.

S1S: Surfaced One Face

S2S: Surfaced Two Faces

S3S: Surfaced Two Faces and Straight Line Ripped One Edge

S4S: Surfaced Two Faces and Straight Line Ripped Two Edges

Texture: The size of the cells in wood, described as ranging from coarse to fine; often confused with grain.

Twist: A form of warp where one corner of a board is not aligned with the others.

Wane: The presence of bark or a lack of wood from any cause along the edge or corner of a piece of lumber.

Warp: Any deviation of the face or edge of a board from flatness, or any edge that is not at right angles to the adjacent face or edge; the most common forms of warp are bow, cup, twist, and crook.