Annual Growth Ring: The layer of wood growth put on a tree during a single growing season. In the Temperate Zone the annual growth rings of many species (e.g., oaks, and pines) are readily distinguished because of differences in the cells formed during the early and late parts of the season. In some Temperate Zone species (black gum and sweetgum) and many tropical species, annual growth rings are not easily recognized.
Bark Pocket: An opening between annual growth rings that contains bark. Bark pockets appear as dark streaks on radial surfaces and as rounded areas on tangential surfaces.
Bird Peck: A small hole or patch of distorted grain resulting from birds pecking through the growing cells in the tree. In shape, bird peck usually resembles a carpet tack with the point towards the bark; bird peck is usually accompanied by discoloration extending for considerable distance along the grain and to a much lesser extent across the grain.
Birdseye: Small localized areas in wood with the fibers indented and otherwise contorted to form few to many small circular or elliptical figures remotely resembling birds’ eyes on the tangential surface. Sometimes found in sugar maple and used for decorative purposes; rare in other hardwood species.
Board Foot: A unit of measurement of lumber represented by a board 1 foot long, 12 inches wide, and 1 inch thick or its cubic equivalent. In practice, the board foot calculation for lumber 1 inch or more in thickness is based on its nominal thickness and width and the actual length. Lumber with a nominal thickness of less than 1 inch is calculated as 1 inch.
Bow: The distortion of lumber in which there is a deviation, in a direction perpendicular to the flat face, from a straight line from end-to-end of the piece.
Burl: (1) A hard, woody outgrowth on a tree, more or less rounded in form, usually resulting from the entwined growth of a cluster of adventitious buds. Such burls are the source of the highly figured burl veneers used for purely ornamental purposes. (2) In lumber or veneer, a localized severe distortion of the grain generally rounded in outline, usually resulting from overgrowth of dead branch stubs, varying from 1/2 inch to several inches in diameter; frequently includes one or more clusters of several small contiguous conical protuberances, each usually having a core or pith but no appreciable amount of end grain (in tangential view) surrounding it.
Cambium: A thin layer of tissue between the bark and wood that repeatedly subdivides to form new wood and bark cells.
Cant: A log that has been slabbed on one or more sides. Ordinarily, cants are intended for resawing at right angles to their widest sawn face. The term is loosely used. (See Flitch).
Cell: A general term for the anatomical units of plant tissue, including wood fibers, vessel members, and other elements of diverse structure and function.
Cellulose: The carbohydrate that is the principal constituent of wood and forms the framework of the wood cells.
Check: A lengthwise separation of the wood that usually extends across the rings of annual growth and commonly results from stresses set up in wood during seasoning.
Compression Wood: Abnormal wood formed on the lower side of branches and inclined trunks of softwood trees. Compression wood is identified by its relatively wide annual rings (usually eccentric when viewed on cross section of branch or trunk), relatively large amount of summerwood, sometimes more than 50 percent of the width of the annual rings in which it occurs, and its lack of demarcation between earlywood and latewood in the same annual rings. Compression wood shrinks excessively lengthwise, as compared with normal wood.
Conditioning: (pre and post) The exposure of a material to the influence of a prescribed atmosphere for a stipulated period of time or until a stipulated relation is reached between material and atmosphere.
Cooperage: Containers consisting of two round heads and a body composed of staves held together with hoops, such as barrels and kegs.
Slack Cooperage – Cooperage used as containers for dry, semidry or solid products. The staves are usually not closely fitted and are held together with beaded steel, wire, or wood hoops.
Tight Cooperage – Cooperage used as containers for liquids, semisolids, and heavy solids. Staves are well fitted and held tightly with cooperage-grade steel hoops.
Crossband: To place the grain of layers of wood at right angles in order to minimize shrinking and swelling; also, in plywood of three or more plies, a layer of veneer whose grain direction is at right angles to that of the face plies.
Cup: A distortion of a board in which there is a deviation flatwise from a straight line across the width of the board.
Cut Stock: A term of softwood stock comparable to dimension parts in hardwoods. (See Dimension Parts).
Cuttings: In hardwoods, portions of a board having the quality required by a specific grade or for a particular use. Obtained from a board by crosscutting or ripping.
Decay: The decomposition of wood substance by fungi.
Advanced (or Typical Decay) – The older stage of decay in which the destruction is readily recognized because the wood has become punky, soft, and spongy, stringy, ringshaked, pitted, or crumbly. Decided discoloration or bleaching of the rotted wood is often apparent.
Incipient Decay – The early stage of decay that has not proceeded far enough to soften or otherwise perceptibly impair the hardness of the wood. It is usually accompanied by a slight discoloration or bleaching of the wood.
Density: As usually applied to wood of normal cellular form, density is the mass of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex having unit volume. It is variously expressed as pounds per cubic foot, kilograms per cubic meter, or grams per cubic centimeter at specified moisture content.
Diffuse-Porous Wood: Certain hardwoods in which the pores tend to be uniform in size and distribution throughout each annual ring or to decrease in size slightly and gradually toward the outer border of the ring.
Dimension Parts: A term largely superseded by the term “hardwood dimension lumber.” It is hardwood stock processed to a point where the maximum waste is left at the mill, and the maximum utility is delivered to the user. It is stock of specified thickness, width, and length or multiples thereof. According to specification it may be solid or glued up, rough or surfaced, semi-fabricated or completely fabricated.
Dote: “Dote,” “doze,” and “rot” are synonymous with “decay” and are any form of decay that may be evident as either a discoloration or a softening of the wood.
Dry Rot: A term loosely applied to any dry, crumbly rot but especially to that which, when in an advanced stage permits the wood to be crushed easily to a dry powder. The term is actually a misnomer for any decay, since all fungi require considerable moisture for growth.
Earlywood: The portion of the annual growth ring that is formed during the early part of the growing season. It is usually less dense and weaker mechanically than latewood.
Edge Grain: (See Grain)
Equilibrium Moisture Content: The moisture content at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature.
Finish (Finishing): Wood products such as doors, stairs, and other fine work required to complete a building, especially the interior. Also, coatings of paint, varnish, lacquer, wax, etc., applied to wood surfaces to protect and enhance their durability or appearance.
Flitch: A portion of a log sawn on two or more faces – commonly on opposite faces leaving two waney edges. When intended for resawing into lumber, it is resawn parallel to its original wide faces. Or, it may be sliced or sawn into veneer, in which case the resulting sheets of veneer laid together in the sequence of cutting are called a flitch. The term is loosely used. (See Cant).
Grain: The direction, size, arrangement, appearance or quality of the fibers in wood or lumber. To have a specific meaning the term must be qualified.
Close-Grained Wood – Wood with narrow, inconspicuous annual rings. The term is sometimes used to designate wood having small and closely spaced pores, but in this sense the term “fine textured” is more often used.
Coarse-Grained Wood – Wood with wide conspicuous annual rings in which there is considerable difference between springwood and summerwood. The term is sometimes used to designate wood with large pores, such as oak, ash, chestnut, and walnut, but in this sense the term “coarse textured” is more often used.
Curly-Grained Wood – Wood in which the fibers are distorted so that they have a curled appearance, as in “birdseye” wood. The areas showing curly grain may vary up to several inches in diameter.
Diagonal-Grained Wood – Wood in which the annual rings are at an angle with the axis of a piece as a result of sawing at an angle with the bark of the tree or log. A form of cross-grain.
Edge-Grained Lumber – Lumber that has been sawed so that the wide surfaces extend approximately at right angles to the annual growth rings. Lumber is considered edge grained when the rings form an angle of 45° to 90° with the wide surface of the piece.
End-Grained Wood – The grain as seen on a cut made at a right angle to the direction of the fibers (e.g., on a cross section of a tree).
Fiddleback-Grained Wood – Figure produced by a type of fine wavy grain found, for example, in species of maple; such wood being traditionally used for the backs of violins.
Fine-Grained Wood – (See Grain.)
Flat-Grained Wood – Lumber that has been sawed parallel to the pith and approximately tangent to the growth rings. Lumber is considered flat grained when the annual growth rings make an angle of less than 45° with the surface of the piece.
Interlocked-Grained Wood – Grain in which the fibers put on for several years may slope in a right-handed direction, and then for a number of years the slope reverses to a left-hand direction, and later changes back to a right-handed pitch, and so on. Such wood is exceedingly difficult to split radially, though tangentially it may split fairly easily.
Open-Grained Wood – Common classification for woods with large pores, such as oak, ash, chestnut, and walnut. Also known as “coarse textured.”
Plainsawn Lumber – Another term for flat-grained lumber.
Quartersawn Lumber – Another term for edge-grained lumber.
Side-Grained Wood – Another term for flat-grained lumber.
Slash-Grained Wood – Another term for flat-grained lumber.
Spiral-Grained Wood – Wood in which the fibers take a spiral course about the trunk of a tree instead of the normal vertical course. The spiral may extend in a right-handed or left-handed direction around the tree trunk. Spiral grain is a form of cross grain.
Straight-Grained Wood – Wood in which the fibers run parallel to the axis of a piece.
Vertical-Grained Lumber – Another term for edge-grained lumber.
Wavy-Grained Wood – Wood in which the fibers collectively take the form of waves or undulations.
Green – Freshly sawn or undried wood. Wood that has become completely wet after immersion in water would not be considered green, but may be said to be in the “green condition.”
Growth Ring – (See Annual Growth Ring)
Gum – A comprehensive term for nonvolatile viscous plant exudates, which either dissolve or swell up in contact with water. Many substances referred to as gums, such as pine and spruce gum, are actually oleoresins.
Hardwoods – Generally one of the botanical groups of trees that have broad leaves in contrast to the conifers or softwoods. The term has no reference to the actual hardness of the wood.
Heart Rot – Any rot characteristically confined to the heartwood. It generally originates in the living tree.
Heartwood – The wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood may contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.
Kiln – A chamber having controlled air-flow, temperature, and relative humidity for drying lumber, veneer, and other wood products.
Compartment Kiln – A kiln in which the total charge of lumber is dried as a single unit. It is designed so that, at any given time, the temperature and relative humidity are essentially uniform throughout the kiln. The temperature is increased as drying progresses, and the relative humidity is adjusted to the needs of the lumber.
Progressive Kiln – A kiln in which the total charge of lumber is not dried as a single unit but as several units, such as kiln truckloads, that move progressively through the kiln. The kiln is designed so that the temperature is lower and the relative humidity higher at the end where the lumber enters than at the discharge end.
Knot – That portion of a branch or limb that has been surrounded by subsequent growth of the stem. The shape of the knot as it appears on a cut surface depends on the angle of the cut relative to the long axis of the knot.
Encased Knot – A knot whose rings of annual growth are not intergrown with those of the surrounding wood.
Intergrown Knot – A knot whose rings of annual growth are completely intergrown with those of the surrounding wood.
Loose Knot – A knot that is not held firmly in place by growth or position and that cannot be relied upon to remain in place.
Pin Knot – A knot that is not more than 1/2 inch in diameter.
Sound Knot – A knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.
Spike Knot – A knot cut approximately parallel to its long axis so that the exposed section is definitely elongated.
Lignin – The second most abundant constituent of wood, located principally in the secondary wall and the middle lamella, which is the thin cementing layer between wood cells. Chemically, it is an irregular polymer of substituted propylphenol groups, and thus no simple chemical formula can be written for it.
Lumber – The product of the saw and planing mill not further manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching.
Boards – Lumber that is nominally less than 2 inches thick and 2 or more inches wide. Boards less than 6 inches wide are sometimes called strips.
Dimension – Lumber with a nominal thickness of from 2 up to but not including 5 inches and a nominal width of 2 inches or more.
Dressed Size – The dimensions of lumber after being surfaced with a planing machine. The dressed size is usually 1/2 to 3/4 inch less than the nominal or rough size. A 2×4-inch stud, for example, actually measures about 1 1/2 by 3 1/2 inches.
Factory and Shop Lumber – Lumber intended to be cut up for use in further manufacture. It is graded on the basis of the percentage of the area that will produce a limited number of cuttings of a specified minimum size and quality.
Matched Lumber – Lumber that is edge dressed and shaped to make a close tongue-and-grooved joint at the edges or end when laid edge to edge or end to end.
Nominal Size – As applied to timber or lumber, the size by which it is known and sold in the market often differs from the actual size.
Patterned Lumber – Lumber that is shaped to a pattern or to a molded form in addition to being dressed, matched, or shiplapped, or any combination of these workings.
Rough Lumber – Lumber that has not been dressed (surfaced) but which has been sawn, edged, and trimmed.
Shiplapped Lumber – Lumber that is edge dressed to make a lapped joint.
Shipping-Dry Lumber – Lumber that is partially dried to prevent stains and mold in transit.
Side Lumber – A board from the outer portion of the log-ordinarily one produced when squaring off a log for a tie or timber.
Structural Lumber – Lumber that is intended for use where allowable properties are required. The grading of structural lumber is based on the strength or stiffness of the piece as related to anticipated uses.
Surfaced Lumber – Lumber that is dressed by running it through a planer.
Timbers – Lumber that is nominally 5 or more inches in least dimensions. Timbers may be used as beams, stringers, posts, caps, sills, girders, purlins, etc.
Yard Lumber – A little-used term for lumber of all sizes and patterns that is intended for general building purposes having no design property requirements.
Manufacturing Defects – Includes all defects or blemishes that are produced in manufacturing, such as chipped grain, loosened grain, raised grain, torn grain, skips in dressing, hit and miss (series of surfaced areas with skips between them), variation in sawing, miscut lumber, machine burn, machine gouge, mismatching, and insufficient tongue-and-groove.
Millwork – Planed and patterned lumber for finish work in buildings, including items such as sash, doors, cornices, panel work, and other items of interior and exterior trim. Does not include flooring, ceiling, or siding.
Mineral Streak – An olive to greenish-black or brown discoloration of undetermined cause in hardwoods.
Modified Wood – Wood processed by chemical treatment, compression, or other means (with or without heat) to impart properties quite different from those of the original wood.
Moisture Content – The amount of water contained in the wood, usually expressed as a percentage of the weight of the ovendry wood.
Moulding – A wood strip having a curved or projecting surface, used for decorative purposes.
Old Growth – Timber in or from a mature, established forest. When the trees have grown during most if not their entire individual lives in active competition with their companions for sunlight and moisture, this timber is usually straight and relatively free of knots.
Pallet – A low wood or metal platform on which material can be stacked to facilitate mechanical handling, moving, and storage.
Peck – Pockets or areas of disintegrated wood caused by advanced stages of localized decay in the living tree. It is usually associated with cypress and incense cedar. There is no further development of peck once the lumber is seasoned.
Pitch Pocket – An opening extending parallel to the annual growth rings and containing, or that has contained, pitch, either solid or liquid.
Pitch Streaks – A well-defined accumulation of pitch in a more or less regular streak in the wood of certain conifers.
Pith – The small, soft core occurring near the center of a tree trunk, branch, twig, or log.
Pith Fleck – A narrow streak, resembling pith on the surface of a piece; usually brownish, up to several inches in length; results from burrowing of larvae in the growing tissues of the tree.
Plank – A broad board, usually more than 1 inch thick, laid with its wide dimension horizontal and used as a bearing surface.
Plywood – A glued wood panel made up of relatively thin layers of veneer with the grain of adjacent layers at right angles, or of veneer in combination with a core of lumber or of reconstituted wood. The usual constructions have an odd number of layers.
Radial – Coincident with a radius from the axis of the tree or log to the circumference. A radial section is a lengthwise section in a plane that passes through the centerline of the tree trunk.
Rays, Wood – Strips of cells extending radially within a tree and varying in height from a few cells in some species to 4 or more inches in oak. The rays serve primarily to store food and transport it horizontally in the tree. On quartersawed oak, the rays form a conspicuous figure, sometimes referred to as flecks.
Reaction Wood – Wood with more or less distinctive anatomical characters, formed typically in parts of leaning and crooked stems and in branches. In hardwoods this consists of tension wood and in softwoods of compression wood.
Sapwood – The wood of pale color near the outside of the log. Under most conditions the sapwood is more susceptible to decay than heartwood.
Saw Kerf – (1) Grooves or notches made in cutting with a saw; (2) that portion of a log, timber, or other piece of wood removed by the saw in parting the material into two pieces.
Seasoning – Removing moisture from green wood to improve its serviceability.<p>    Air-Dried – Dried by exposure to air in a yard or shed, without artificial heat.
Kiln-Dried – Dried in a kiln with the use of artificial heat.
Second Growth – Timber that has grown after the removal, whether by cutting, fire, wind, or other agency, of all or a large part of the previous stand.
Shake – A separation along the grain, the greater part of which occurs between the rings of annual growth. Usually considered to have occurred in the standing tree or during felling.
Shaving – A small wood particle of indefinite dimensions developed incidental to certain woodworking operations involving rotary cutterheads usually turning in the direction of the grain. This cutting action produces a thin chip of varying thickness, usually feathered along at least one edge and thick at another and generally curled.
Shear – A condition of stress or strain where parallel planes slide relative to one another.
Soft Rot – A special type of decay developing under very wet conditions (as in cooling towers and boat timbers) in the outer wood layers, caused by cellulose-destroying microfungi that attack the secondary cell walls and not the intercellular layer.
Softwoods – Generally, one of the botanical groups of trees that in most cases have needlelike or scalelike leaves, the conifers, also the wood produced by such trees. The term has no reference to the actual hardness of the wood.
Specific Gravity – As applied to wood, the ratio of the ovendry weight of a sample to the weight of a volume of water equal to the volume of the sample at a specified moisture content (green, air-dry, or ovendry).
Stain – A discoloration in wood that may be caused by such diverse agencies as micro-organisms, metal, or chemicals. The term also applies to materials used to impart color to wood.
Blue Stain – A bluish or grayish discoloration of the sapwood caused by the growth of certain dark-colored fungi on the surface and in the interior of the wood; made possible by the same conditions that favor the growth of other fungi.
Brown Stain – A rich brown to deep chocolate-brown discoloration of the sapwood of some pines caused by a fungus that acts much like the blue-stain fungi.
Chemical Brown Stain – A chemical discoloration of wood, which sometimes occurs during the air-drying or kiln drying of several species, apparently caused by the concentration and modification of extractives.
Sap Stain – (See Stain)
Sticker Stain – A brown or blue stain that develops in seasoned lumber where it has been in contact with the stickers.
Stickers – Strips or boards used to separate the layers of lumber in a pile and thus improve air circulation.
Stringer – A timber or other supports for cross members in floors or ceilings. In stairs, the support on which the stair treads rest.
Structural Timbers – Pieces of wood of relatively large size, the strength or stiffness of which is the controlling element in their selection and use. Examples of structural timbers are trestle timbers (stringers, caps, posts, sills, bracing, bridge ties, guardrails); car timbers (car framing, including upper framing, car sills); framing for building (posts, sills, girders); ship timber (ship timbers, ship decking); and crossarms for poles.
Stud – One of a series of slender wood structural members used as supporting elements in walls and partitions.
Tension Wood – Abnormal wood found in leaning trees of some hardwood species and characterized by the presence of gelatinous fibers and excessive longitudinal shrinkage. Tension wood fibers hold together tenaciously, so that sawed surfaces usually have projecting fibers, and planed surfaces often are torn or have raised grain. Tension wood may cause warping.
Texture – A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between earlywood and latewood. In this book, texture refers to the finer structure of the wood (see Grain) rather than the annual rings.
Twist – A distortion caused by the turning or winding of the edges of a board so that the four corners of any face is no longer in the same plane.
Wane – Bark or lack of wood from any cause on edge or corner of a piece except for eased edges.
Warp – Any variation from a true or plane surface. Warp includes bow, crook, cup, and twist, or any combination thereof.
Weathering – The mechanical or chemical disintegration and discoloration of the surface of wood caused by exposure to light, the action of dust and sand carried by winds, and the alternate shrinking and swelling of the surface fibers with the continual variation in moisture content brought by changes in the weather. Weathering does not include decay.