Glossary
- Annual growth ring
- The growth layer put on in a single growth year, including springwood and summerwood.
- Bark
- Outer layer of a tree, comprising the inner bark, or thin, inner living part (phloem) and the outer bark, or corky layer, composed of dry, dead tissue.
- Beam
- A structural member supporting a load applied transversely to it.
- Bending, steam
- The process of forming curved wood members by steaming or boiling the wood and bending it to a form.
- Bird’s-eye
- 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. Common in sugar maple and used for decorative purposes: rare in other hardwood species.
- Bow
- The distortion in a board that deviates from flatness lengthwise but not across its faces.
- Broad-leaved trees
- (See Hardwoods.)
- Cambium
- The one-cell-thick layer of tissue between the bark and wood that repeatedly subdivides to form new wood and bark cells.
- Cell
- A general term for the minute units of wood structure, including wood fibers, vessels members, and other elements of diverse structure and function.
- Check
- A lengthwise separation of the wood, usually extending across the rings of annual growth and commonly resulting from stresses set up in the wood during seasoning.
- Collapse
- The flattening of groups of cells in heartwood during the drying or pressure treatment of wood, characterized by a caved-in or corrugated appearance.
- Crook
- The distortion in a board that deviates edgewise from a straight line from end to end of the board.
- Cup
- The distortion in a board that deviates flatwise from a straight line across the width of the board.
- 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
- The weight of a body per unit volume. When expressed in the c. g. s. (centimeter-gram-second) system, it is numerically equal to the specific gravity of the same substance.
- 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
- (See Lumber.)
- Dimension stock
- 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 a dimension mill, and the maximum utility is delivered to the user. It is stock of specified thickness, width, and length, in multiples thereof. According to specification, it may be solid or glued; rough or surfaced; semifabricated or completely fabricated.
- Dimensional stabilization
- Reduction through special treatment in swelling and shrinking of wood, caused by changes in its moisture content with changes in relative humidity.
- Dry kiln
- (See Kiln.)
- 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, since all wood-rotting fungi require considerable moisture for growth.
- Early wood
- (See Springwood.)
- Edge-grained
- (See Grain.)
- Extractives
- Substances in wood, not an integral part of the cellular structure, that can be removed by solution in hot or cold water, ether, benzene, or other solvents that do not react chemically with wood components.
- Fiber, wood
- A comparatively long (one twenty-fifth or less to one-third inch), narrow, tapering wood cell closed at both ends.
- Figure
- The pattern produced in a wood surface by annual growth rings, rays, knots, deviations from regular grain such as interlocked and wavy grain, and irregular coloration.
- Finish
- Wood products to be used in the joiner work, such as doors and stairs, and other fine work required to complete a building, especially the interior.
- Flakes
- (See Rays, wood.)
- Flat-grained
- (See Grain.)
- Framing
- Lumber used for the structural members of a building, such as studs and joists.
- Girder
- A large or principal beam used to support concentrated loads at points along its length.
- Grade
- The designation of quality of a manufactured piece of wood or of logs.
- Grain
- The direction, size, arrangement, appearance, or quality of the elements 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.
- Cross-grained wood
- Wood in which the fibers deviate from a line parallel to the sides of the piece. Cross grain may be either diagonal or spiral grain, or a combination of the two.
- Curly-grained wood
- Wood in which the fibers are distorted so that they have a curled appearance, as in “bird’s-eye” 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.
- Fine-grained wood
- (See Grain, close-grained wood.)
- Flat-grained lumber
- Lumber that has been sawed so the wide surfaces extend approximately parallel to the annual 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-arained wood
- Wood in which the fibers are inclined in one direction in a number of rings of annual growth, then gradually reverse and are inclined in an opposite direction in succeeding growth rings, then reverse again.
- Open-grained wood
- Common classification by painters for woods with large pores, such as oak, ash, chestnut, and walnut. Also known as “coarse textured.” Plainsawed lumber.—Another term for flat-grained lumber.
- Quartersawed lumber
- Another term for edge-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 sawed lumber, or lumber that has received no intentional drying; unseasoned. The term does not apply to lumber that may have become completely wet through waterlogging.
- Hardwoods
- Generally, the botanical group 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.
- 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 be infiltrated with gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.
- Honeycombing
- Checks, often not visible at the surface, that occur in the interior of a piece of wood, usually along the wood rays.
- Joint
- The junction of two pieces of wood or veneer.
- Joist
- One of a series of parallel beams used to support floor and ceiling loads and supported in turn by larger beams, girders,-or bearing walls.
- Kiln
- A heated chamber for drying lumber, veneer, and other wood products.
- Knot
- That portion of a branch or limb which has been surrounded by subsequent growth of the wood of the trunk or other portion of the tree. As a knot appears on the sawed surface, it is merely a section of the entire knot, its shape depending upon the direction of the cut.
- Longitudinal
- Generally, the direction along the length of the grain of wood.
- Lumber
- The product of the saw and planing mill, not further manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, cross-cutting to length, and matching.
- Boards
- Yard lumber less than 2 inches thick and 1 or more inches wide.
- Dimension
- Lumber from 2 inches to, but not including 5 inches thick, and 2 or more inches wide.
- Dressed size
- The dimensions of lumber after shrinking from the green dimensions and being surfaced with a planing machine to usually 3/8 or ½ inch less than the nominal or rough size. For example, a 2- by 4-inch stud actually measures 1 5/8 by 3 5/8 inches under American lumber standards for softwood lumber.
- Nominal size
- As applied to timber or lumber, the rough-sawed commercial size by which it is known and sold in the market.
- Structural lumber
- Lumber that is 2 or more inches thick and 4 or more inches wide. intended for use where working stresses are required. The grading of structural lumber is based on the strength of the piece and the use of the entire piece.
- Timbers
- Lumber 5 or more inches in least dimension. Timbers may be classified as beams, stringers, posts, caps, sills, girders, purlins, etc.
- Medullary rays
- (See Rays, wood.)
- Millwork
- Generally, all building materials made of finished wood and manufactured in millwork plants and planing mills. Includes such items as inside and outside doors, window and door frames, blinds, porch work, mantels, panel work, stairways, moldings, and interior trim. Does not include flooring, ceiling, or siding.
- Moisture content of wood
- The amount of water contained in the wood. Usually expressed as a percentage of the weight of the ovendry wood.
- Naval stores
- A term applied to the oils, resins, tars, and pitches derived from oleoresin contained in, exuded by, or extracted from trees chiefly of the pine species (genus Pinus) or from the wood of such trees.
- Old growth
- Timber growing in or harvested from a mature, naturally established forest. When the trees have grown most or all of their individual lives in active competition with their companions for sunlight and moisture, this timber is usually straight and relatively free of knots.
- Ovendry wood
- Wood dried to constant weight in an oven at temperatures above that of boiling water (usually 101° to 105° C. or 214° to 221° F.).
- 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 incensecedar. There is no further development of peck once the lumber is seasoned.
- Pitch pocket
- An opening that extends parallel to the annual growth rings and that contains, or has contained, either solid or liquid pitch.
- Pitch streak
- A well-defined accumulation of pitch in a more or less regular streak in the wood of certain softwoods.
- Pith
- The small, soft core occurring in the structural center of a tree trunk, branch, twig, or log.
- Plainsawed
- (See Grain.)
- Planing-mill products
- Products worked to pattern, such as flooring, ceiling, and siding.
- Plywood
- An assembly made of layers (plies) of veneer, or of veneer in combination with a lumber core, joined with an adhesive. The grain of adjoining plies is usually laid at right angles, and almost always an odd number of plies are used to obtain balanced construction.
- Pore
- (See Vessels.)
- Porous woods
- Another name for hardwoods, which frequently have vessels or pores large enough to be seen readily without magnification.
- Preservative
- Any substance that is effective, for a reasonable length of time, in preventing the development and action of wood-rotting fungi, borers of various kinds, and harmful insects that deteriorate wood.
- Quartersawed
- (See Grain.)
- 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 extends from pith to bark.
- Rate of growth
- The rate at which a tree has laid on wood measured radially in the trunk or in lumber cut from the trunk. The unit of measure in use is number of annual growth rings per inch.
- 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.
- Resin passage (or duct)
- Intercellular passages that contain and transmit resinous materials. On a cut surface, they are usually inconspicuous. They may extend vertically parallel to the axis of the tree or at right angles to the axis and parallel to the rays.
- Ring-porous woods
- A group of hardwoods in which the pores are comparatively large at the beginning of each annual ring and decrease in size more or less abruptly toward the outer portion of the ring, thus forming a distinct inner zone of pores, known as the springwood, and an outer zone with smaller pores, known as the summerwood.
- Sap
- All the fluids in a tree except special secretions and excretions, such as oleoresin.
- Sapwood
- The living wood of pale color near the outside of the log. Under most conditions the sapwood is more susceptible to decay than heartwood.
- Seasoning
- Removing moisture from green wood in order to improve its serviceability.
- Air-dried
- Dried by exposure to air, usually in a yard, without artificial heat.
- Kiln-dried
- Dried in a kiln with the use of artificial heat.
- Second growth
- Timber that has grown after removal by cutting, fire, wind, or other agency, of all or a large part of the previous stand.
- Sheathing
- The structural covering, usually of boards or fiberboards, placed over exterior studding or rafters of a structure.
- Softwoods
- Generally, the botanical group of trees that bear cones and in most cases have needlelike or scalelike leaves; also the wood produced by such trees. The term has no reference to the actual hardness of the wood.
- Specific gravity
- The radio of the weight of a body to the weight of an equal volume of water at 4° C. or other specified temperature.
- Springwood
- The portion of the annual growth ring that is formed during the early part of the season’s growth. In most softwoods and in ring-porous hardwoods, it is less dense and weaker mechanically than summerwood.
- 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 color wood.
- Strength
- The term in its broader sense includes all the properties of wood that enable it to resist different forces or loads. In its more restricted sense, strength may apply to any one of the mechanical properties, in which event the name of the property under consideration should be stated. thus: strength in compression parallel to grain, strength in bending, hardness, and so on.
- Stess
- Force per unit of area.
- Stud
- One of a series of slender wood structural members used as supporting elements in walls and partitions.
- Summerwood
- The portion of the annual growth ring that is formed after the springwood formation has ceased. In most softwoods and in ring-porous hardwoods, it is denser and stronger mechanically than springwood.
- Tangential
- Strictly, coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent. In practice, however, it often means roughly coincident with a growth ring. A tangential section is a longitudinal section through a tree or limb and is perpendicular to a radius. Flat-grained and plainsawed lumber is sawed tengentially.
- Texture
- A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between springwood and summerwood. In this publication, 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 are no longer in the same plane.
- Tyloses
- Masses of cells appearing somewhat like froth in the pores of some hardwoods, notably white oak and black locust. In hardwoods, tyloses are formed when walls of living cells surrounding vessels extend into the vessels. They are sometimes formed in softwoods in a similar manner by the extension of cell walls into resin-passage cavities.
- Veneer
- A thin layer or sheet of wood cut on a veneer machine.
- Rotary-cut veneer
- Veneer cut in a lathe which rotates a log or bolt, chucked in the center, against a knife.
- Sawed veneer
- Veneer produced by sawing.
- Sliced veneer
- Veneer that is sliced off a log, bolt, or flitch with a knife.
- Vertical grain
- (See Grain.)
- Vessels
- Wood cells of comparatively large diameter that have open ends and are set one above the other so as to form continuous tubes. The openings of the vessels on the surface of a piece of wood are usually referred to as pores.
- Virgin growth
- The original growth of mature trees.
- Wane
- Bark or lack of wood from any cause on the edge or corner of a piece of lumber.
- 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 that is 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.
- Wood substance
- The solid material of which wood is composed. It usually refers to the extractive-free solid substance of which the cell walls are composed, but this is not always true. There is no wide variation in chemical composition or specific gravity between the mood substance of various species; the characteristic differences of species are largely due to differences in infiltrated materials and variations in relative amounts of cell walls and cell cavities.
- Workability
- The degree of ease and smoothness of cut obtainable with hand or machine tools.