Adhesive: A substance capable of holding materials together by surface attachment. It is a general term and includes cements, mucilage, and paste, as well as glue.
Anisotropic: Exhibiting different properties when measured along different axes. In general, fibrous materials such as wood are anisotropic.
Balanced Construction: A construction such that the forces induced by uniformly distributed changes in moisture content will not cause warping. Symmetrical construction of plywood in which the grain direction of each ply is perpendicular to that of adjacent plies is balanced construction.
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.
Beam: A structural member supporting a load applied transversely to it.
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.
Blister: An elevation of the surface of an adherend, somewhat resembling in shape a blister on human skin; its boundaries may be indefinitely outlined, and it may have burst and become flattened. (A blister may be caused by insufficient adhesive; inadequate curing time, temperature, or pressure; or trapped water, or solvent vapor.)
Board Foot: A unit of measurement of lumber represented by a board 12 in. long, 12 in. wide, and 1 in. thick, or its cubic equivalent. In practice, the board foot calculation for lumber 1 in. 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 in. is calculated as 1 in.
Bond: (1) The union of materials by adhesive. (2) To unite materials by means of an adhesive.
Bond Strength: The unit load applied in tension, compression, flexure, peel impact, cleavage, or shear required to break an adhesive assembly, with failure occurring in or near the plane of the bond.
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.
Box Beam: A built-up beam with solid wood flanges and plywood or wood-based panel product webs.
Boxed Heart: The term used when the pith falls entirely within the four faces of a piece of wood anywhere in its length. Also called boxed pith.
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 one to several centimeters (one-half to several inches) in diameter; frequently includes one or more clusters of several small contiguous conical protuberances, each usually having a core or a 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)
Casehardening: A condition of stress and set in dry lumber characterized by compressive stress in the outer layers and tensile stress in the center or core.
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 principle 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.
Cohesion: The state in which the constituents of a mass of material are held together by chemical and physical forces.
Compression Failure: Deformation of the wood fibers resulting from excessive compression along the grain either in direct end compression or in bending. It may develop in standing trees due to bending by wind or snow or to internal longitudinal stresses developed in growth, or it may result from stresses imposed after the tree is cut. In surfaced lumber, compression failures may appear as fine wrinkles across the face of the piece.
Corbel: A projection from the face of a wall or column supporting a weight.
Crook: The distortion of lumber in which there is a deviation, in a direction perpendicular to the edge, from a straight line from end-to-end of the piece.
Decay: The decomposition of wood substance by fungi.
Advanced (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.
Brown Rot: In wood, any decay in which the attack concentrates on the cellulose and associated carbohydrates rather than the lignin, producing a light to dark brown friable residue – hence loosely termed "dry rot." An advanced stage where the wood splits along rectangular planes, in shrinking, is termed "cubical rot."
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.
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.
Heart Rot: Any rot characteristically confined to the heartwood. It generally originates in the living tree.
Pocket Rot: Advanced decay that appears in the form of a hole or pocket, usually surrounded by apparently sound wood.
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.
White Rot: In wood, any decay or rot attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy rot, or occur as pocket rot.
Delamination: The separation of layers in laminated wood or plywood because of failure of the adhesive, either within the adhesive itself or at the interface between the adhesive and the adherend.
Density: As usually applied to wood of normal cellular form, density is the mass per unit volume of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex. It is variously expressed as pounds per cubic foot, kilograms per cubic meter, or grams per cubic centimeter at a specified moisture content.
Dew Point: The temperature at which a vapor begins to deposit as a liquid. Applies especially to water in the atmosphere.
Early Wood: The portion of the growth ring that is formed during the early part of the growing season. It is usually less dense and weaker mechanically than latewood. Also known as Springwood.
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.
Fiber Saturation Point: The stage in the drying or wetting of wood at which the cell walls are saturated and the cell cavities free from water. It applies to an individual cell or group of cells, not to whole boards. It is usually taken as approximately 30% moisture content, based on oven-dry weight.
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.
Filler: In woodworking, any substance used to fill the holes and irregularities in planed or sanded surfaces to decrease the porosity of the surface before applying finish coatings. As applied to adhesives, a relatively non-adhesive substance added to an adhesive to improve its working properties, strength, or other qualities.
Finish (Finishing): (1) Wood products such as doors, stairs, and other fine work required to complete a building, especially the interior. (2) Coatings of paint, varnish, lacquer, wax, or other similar materials applied to wood surfaces to protect and enhance their durability or appearance.
Glue: Originally, a hard gelatin obtained from hides, tendons, cartilage, bones, etc., of animals. Also, an adhesive prepared from this substance by heating with water. Through general use the term is now synonymous with the term "adhesive."
Grade: The designation of the quality of a manufactured piece of wood or of logs.
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 (Fine-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 early wood and latewood. The term is sometimes used to designate wood with large pores, such as oak, keruing, meranti, and walnut, but in this sense, the term "open-grained" 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 "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 (such as on a cross section of a tree).
Fiddleback-Grained Wood: Figure produced by a type of fine wavy grain found, for example, in species such as maple; such wood being traditionally used for the backs of violins.
Flat-Grained (Flat-Sawn) Lumber: Lumber that has been sawn 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-handed 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, keruing, meranti, 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 limber.
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: The layer of wood growth put on a tree during a single growth season. In the temperate zone, the annual growth rings of many species (for example, 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 sweet gum) and many tropical species, annual growth rings are not easily recognized.
Hardness: A property of wood that enables it to resist indentation.
Hardwoods: Generally one of the botanical groups of trees that have vessels or pores and 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 contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.
Isotropic: Exhibiting the same properties in all directions.
Joint: The junction of two pieces of wood or veneer.
Adhesive Joint: The location at which two adherends are held together with a layer of adhesive.
Butt Joint: An end joint formed by abutting the squared ends of two pieces.
Edge Joint: A joint made by bonding two pieces of wood together edge-to-edge, commonly by gluing. The joints may be made by gluing two squared edges as in a plain edge joint or by using machined joints of various kinds, such as tongued-and-grooved joints.
End Joint: A joint made by bonding two pieces of wood together end-to-end, commonly by end matching.
Finger Joint: An end joint made up of several meshing wedges or fingers of wood bonded together with an adhesive. Fingers are sloped and may be cut parallel to either the wide or narrow face of the piece.
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 chamber having controlled air-flow, temperature, and relative humidity for drying lumber. The temperature is increased as drying progresses, and the relative humidity is decreased.
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 inter-grown with those of the surrounding wood.
Inter-grown Knot: A knot whose rings of annual growth are completely inter-grown 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 12mm (1/2 in.) 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.
Laminate: A product made by bonding together two or more layers (laminations) of material or materials.
Laminated Timbers: An assembly made by bonding layers of veneer or lumber with an adhesive so that the grain of all laminations is essentially parallel.
Latewood: The portion of the growth ring that is formed after the early wood formation has ceased. It is usually denser and stronger than early wood. (Also known as summer wood.)
Lumber: The product of the saw and planning mill for which manufacturing is limited to sawing, resawing, passing lengthwise through a standard planning machine, crosscutting to length, and matching. Lumber may be made from either softwood or hardwood. (See also Lumber: Dimension.)
Board: Lumber that is less than 38 mm standard (2 in. nominal) thickness and greater than 38 mm standard (2 in. nominal) width. Boards less than 140 mm standard (6 in. nominal) width are sometimes called strips.
Dimension: Lumber with a thickness from 38 mm standard (2 in. nominal) up to but not including 114 mm standard (2 in. nominal).
Dressed Size: The dimensions of lumber after being surfaced with a planning machine. The dressed size is usually ½ to ¾ in. less than the nominal or rough size. A 2-by-4 in. stud, for example, actually measures about 1 ½ by 3 ½ in. (standard 38-by-89 mm).
Factory and Shop Lumber: Lumber intended to be cut up for use in further manufacture. It is graded on 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 tongued-and-grooved joint at the edges or ends 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 has been sawed, edged, and trimmed.
Surfaced Lumber: Lumber that is dressed by running it through a planer.
Timbers: Lumber that is standard 114 mm (nominal 5 in.) or more in at least dimension. Timbers may be used as beams, stringers, posts, caps, sills, girders, or purlins.
Mastic: A material with adhesive properties, usually used in relatively thick sections that can be readily applied by extrusion, trowel, or spatula. (See Adhesive.)
Millwork: Planed and patterned lumber for finish work in building, including items such as sash, doors, cornices, panelwork, and other items of interior or exterior trim. Does not include flooring, ceiling, or siding.
Mineral Streak: An olive to greenish-black or brown discoloration of undetermined cause in hardwoods.
Moisture Content: The amount of water contained in the wood, usually expressed as a percentage of the weight of the ovendry wood.
Molding: A wood strip having a curved or projecting surface, used for decorative purposes.
Mortise: A slot cut into a board, plank, or timber to form a joint.
Naval Stores: A term applied to the oils, resins, tars, and pitches derived from oleoresin contained in, exuded by, or extracted from trees, chiefly species of pines ( genus Pinus). Historically, these were important items in the stores of wood sailing vessels.
Old Growth: Timber in or from a mature, naturally established forest. When the trees have grown during most if not 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 a relatively constant weight in a ventilated oven at 102°C to 105°C (215°F to 220°F).
Parenchyma: Short cells having simple pits and functioning primarily in the metabolism and storage of plant food materials. They remain alive longer than tracheids, fibers, and vessel elements, sometimes for many years. Two kinds of parenchyma cells are recognized – those in vertical strands, known more specifically as axial parenchyma, and those in horizontal series in the rays, and known as ray parenchyma.
Pile: A long, heavy timber, round or square, that is driven deep into the ground to provide a secure foundation for structures built on soft, wet, or submerged sites (for example, landing stages, or bridge abutments).
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.
Plank: A broad, thick board 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.
Psychrometer: An instrument for measuring the amount of water vapor in the atmosphere. It has both a dry-bulb and a wet-bulb thermometer. The bulb of the wet-bulb thermometer is kept moistened and is, therefore, cooled by evaporation to a temperature lower than that shown by the dry-bulb thermometer. Because evaporation is greater in dry air, the difference between the two thermometer readings will be greater when the air is dry than when it is moist.
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.
Raised Grain: A roughened condition of the surface of dressed lumber in which the hard latewood is raised above the softer early wood but not torn loose from it.
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 quartersawn oak, the rays form a conspicuous figure, sometimes referred to as flecks.
Relative Humidity: Ratio of the amount of water vapor present in the air to that which the air would hold at saturation at the same temperature. It is usually considered on the basis of the weight of the vapor but, for accuracy, should be considered on the basis of vapor pressures.
Resin: (1) Solid, semisolid, or pseudo solid resin – An organic material that has a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures Concho dally. (2) Liquid resin – An organic polymeric liquid that, when converted to its final state for use, becomes a resin.
Resin Ducts: 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 Failure: A separation of the wood during seasoning, occurring along the grain and parallel to the growth rings. (See Shake.)
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 early wood, and an outer zone with smaller pores, known as the latewood.
Rip: To cut lengthwise, parallel to the grain.
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 the green wood to improve its serviceability.
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.
Softwoods: Generally, one of the botanical groups of trees that have no vessels and in most cases, have needlelike or scale like leaves, the conifers, also the wood produced by such trees. The term has no reference to the actual hardness of the wood.
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.
Strength: (1) The ability of a member to sustain stress without failure. (2) In a specific mode of test, the maximum stress sustained by a member loaded to failure.
Strength Raito: The hypothetical ratio of the strength of a structural member to that which it would have if it contained no strength-reducing characteristics (such as knots, slope-of-grain, shake).
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 cross arms for poles.
Substrate: A material upon the surface of which an adhesive-containing substance is spread for any purpose, such as bonding or coating.
Tack: The property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and adherend are brought into contact under low pressure.
Texture: A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between early wood and latewood. In this handbook, texture refers to the finer structure of the wood (see Grain) rather than the annual rings.
Timbers, Round: Timbers used in the original round form, such as poles, pilings, posts, and mine timbers.
Timber, Standing: Timber still on the stump.
Trim: The finish materials in a building, such as moldings, applied around openings (window trim, door trim) or at the floor and ceiling of rooms (baseboard, cornice, and other moldings).
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.
Vapor Retarder: A material with a high resistance to vapor movement, such as foil, plastic film, or specially coated paper that is used in combination with insulation to control condensation.
Veneer: A thin layer or sheet of wood.
Rotary-Cut Veneer: Veneer cut in a lathe that rotates a log or bolt, chucked in the center, against a knife.
Sawn Veneer: Veneer produced by sawing.
Sliced Veneer: Veneer that is sliced off a log, bolt, or flitch with a knife.
Virgin Growth: The growth of mature trees in the original forests.
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.
Water Repellent: A liquid that penetrates wood that materially retards changes in moisture content and dimensions of the dried wood without adversely altering its desirable properties.
Water-Repellent Preservative: A water repellent that contains a preservative that, after application to wood and drying, accomplishes the dual purpose of imparting resistance to attack by fungi or insects and also retards changes in moisture content.
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.
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