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 Glossary of timber terms

[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]

Actual size: The dimensions obtained when an individual piece of lumber is measured with a caliper and tape.

Air-dried: Lumber that was dried by exposure to air in a yard or shed, without artificial heat.A

Air-dry: Timber dried by exposure to air, to 20% moisture or below.

Anisotropic: Exhibiting different properties when measured along different axes.  In general, fibrous materials such as wood are anisotropic.

Arris: The sharp edge or ridge formed by two surfaces meeting at an angle, as in a molding. 

Backcut: The final cut in felling a tree by hand, made on the side opposite the intended direction of fall, after the undercut.

Back-sawing: Sawing timber so that the annual rings, as seen from the end-section, form an angle of less than 45o with the board face. Also known as flat-sawing.

Back-sawn: Timber is backsawn
Fully flatsawn and quartersawn boards
(or flat-sawn) if the growth rings as seen from the end section meet the face of the board at an angle less than 45o with the board face.

Band saw: A saw made from steel, butt welded into an endless belt or band with teeth on one or both edges arranged to cut sequentially.

Band sawmill: An evolution in sawmill technology that uses a thinner band saw blade (less kerf therefore less sawdust waste) than a circular saw. 

Bark-encased knot: A knot fully surrounded by bark as seen on the surface. Classed as a void.

Bark pocket: A small area of bark around which normal wood has grown; 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. 

Black knot: A knot whose colour is significantly darker than the surrounding timber. Can be either a tight intergrown knot or a loose knot

Blackheart: Black or brown discolouration around the centre heartwood of some species. Not necessarily associated with decay.

Blanked: Timber machined to four sides in preparation for finished dimension profiling.

Blanks: Laminated panels sold as a dimensioned product suitable for further sizing and finishing into a more specific end-use.

Block-stack: Sawn timber stacked without filleting.

Bow: Bow is the lengthwise curvature of the broad face of a piece of sawn timber.

Box grade: Timber rejected as not meeting the grading rules.

Brad nail: Small nails used in brad guns.

Brash: a timber term meaning brittle short grained wood

Breastbench: A manually fed bench-mounted circular saw used to resaw sections of the log after the breaking down stage (also called a saw-bench).

Brittle-heart: Wood of abnormal brittleness resulting from compression failure caused by growth stress. Commonly occurs towards the centre of logs of hardwood species.

Burl: A swirl or twist in the grain of wood, usually occurring near a knot, but which itself does not contain a knot.  Valued as the source of highly-figured burl veneers used for ornamental purposes.

Butt: Bottom of a felled part of a tree; large end of a log.

Butt log: First log cut above the stump.

Butt rot: Decay or rot characteristically confined to the base or lower bole of a tree.

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Call size (or dimension): The dimensions by which timber is referred to in commercial transactions. Also called nominal size. The size
Call sizes (mm) 25 40 50 75 100 125 150 200 225 250 300
Actual dressed dry size (mm) 19 35 45 70 90 115 140 180 205 230 280
by which timber is known and sold in the market; often differs from the actual size (e.g. 100x50 is actually dressed to 90x45). This "named" size may vary from the actual size of the piece of wood because variations due to sawing and shrinkage mean the seasoned timber is dressed to a consistent and smaller size.

Cant: Segment of a log which has been sawn on two or more faces to give final product width but which requires further resawing to produce final thickness-dimensioned material.

Case-hardening: A condition of stress-and-set in dry wood in which the outer fibers are under compressive stress and the inner fibers under tensile stress.  The stresses persist after the lumber is dry and cause warp if the wood is remachined after drying.

CCA: Copper Chrome Arsenate, a wood preservative.

Cellulose: The carbohydrate that is the principal constituent of wood and forms the framework of the wood cells.

Check, internal: A crack in the timber below the surface as a result of seasoning.

Check, knot: A check which occurs in a knot.

Check, surface: A visible crack on the surface of the timber resulting from seasoning.

Chip out: tears in wood from planing

Circular sawmill: The traditional sawmill uses a circular saw. Circular saws are thicker (larger kerf) than band saws and produce more waste (sawdust). 

Clearwood: timber graded to be free or practically free of defects and feature.

Coarse-textured: Wood with large pores.

Cold-climate eucalypts: Species within the ash group of eucalypts and Eucalyptus nitens.

Collapse: Excessive and uneven shrinkage causing corrugation of the wood surface. Characterised by a caved-in or corrugated ("washboarded") appearance of the wood surface. Flattening of single cells or rows of cells takes place during the drying or pressure treatment of the wood.

Compression failure: A deformation or fracture of the wood fibres across the grain resulting from excessive compression parallel to the grain. It appears as a minute fracture and is often difficult to detect until the timber is machined. Deformation of the wood fibres in dressed timber may appear as fine wrinkles across the face of the piece. May be caused by growth stresses or felling. Also called "compression fractures", "brittle heart", "shakes" or "thunder-shakes" (when resulting from felling). 

Compression wood: Abnormal wood formed on the lower side of branches and inclined trunks of softwood trees.  Compression wood can be identified by relatively wide annual rings that are eccentric when viewed on cross section of the branch or trunk and a much larger amount of earlywood than latewood. Compression wood shrinks excessively lengthwise compared with normal wood.

Consignment: A quantity of timber that was specified in an order and delivered.

Conventional kiln: Wood is dried by controlling the moisture, temperature and air circulation. Heat is introduced via heat exchangers and warm humid air is removed via vents while cool dry air is introduced, usually at the other end of the kiln. Drying of hardwoods may require increased humidity such as introducing steam or water misting to slow the drying process.

Conversion return: A log recovery value which represents the theoretical maximum amount to pay for logs delivered to the sawmill (Alzamora & Apiolaza 2010). It is estimated from the value of the timber recovered from the log minus the cost of harvesting, cartage, and sawmilling.

Corewood: also known as the heart or inner heart, is the wood adjacent to and including the pith that is within 50 mm of the centre of the pith.

Crook: Also known as spring. The lengthwise curvature of the edge of a piece of sawn timber. Crook refers to longitudinal bending, caused by the outside portion of the log being in longitudinal tension and the core being in longitudinal compression, causing the log to split when crosscut and planks to bend longitudinally when rip sawn to boards.

Crosscut: Cutting across the grain, e.g., a “crosscut” saw.

Cross-grain: Fibres that deviate from a line parallel to the sides of the piece.

Cross section: The width of the piece of timber multiplied by the thickness. This can be at a specified point in the length of the board. 

Cube: A cubic metre of timber.

Cup: Cupping is the deviation in the face of a piece of lumber from a straight line drawn from edge to edge of a piece of lumber.

Cut, face: A cut made without using the saw bench's fence or sizing mechanism. An undimensioned cut which is used to produce a straight edge or face

Cut of Log: Green sawn ungraded timber.

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DBH: Diameter at breast height

Decay: The decomposition of wood substance caused by the action of wood- destroying fungi, resulting in softening, loss of strength, weight, and often in change of texture and color. Wood with a moisture content of less than 20% will not decay.

Decay, butt-rot: Decay or rot characteristically confined to the base or lower bole of a tree.

Decay, dry rot: Any decay in wood in which the attack is confined to the cellulose and associated carbohydrates rather than the lignin, producing a light to dark brown friable residue. Also known as brown rot.

Decay, incipient: Early stages of decay in wood in which the color has changed but the strength and hardness have not yet been affected. Also called "dote".

Decay, white rot: Decay attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy.

Defect: A characteristic of timber that makes it either less desirable or completely unsuitable for the intended purpose.

Defect containment: Sawing pattern which attempts to maximise the proportion of defect-free sawn timber produced by turning the log and restricting the defect to a low-grade central flitch.

Degrade: Drop in lumber grade due to manufacturing or drying practices.

Dehumidifier kiln: A kiln working on the heat pump principle and evaporating moisture from the timber by a flow of warm air condensed on evaporator coils of a refrigeration unit and drained away. The refrigerant is compressed and passed through condenser coils, re-heating the air stream. Sometimes additional heat is applied in the early stages of drying.

Delamination: The separation of the layers of laminated wood or plywood at the glueline, usually caused by moisture, mismanufacture, or defective glue.

Density, wood: The mass of wood substance having unit volume.  Expressed as kilograms per cubic metre at a specified moisture content.

Deviation, sawing: The deviation from target sawn sizes resulting from sawing.

Dimension, dressed: The dimensions of lumber after being surfaced with a planing machine.

Dimension, nominal: The named size which may vary from the actual size of the piece of wood because of variations due to sawing, shrinkage and dressing and the tolerances allowed for these operations. The size by which timber is known and sold in the market; often differs from the actual size (e.g. 100x50 is actually dressed to 90x45).

Distortion: Distortion
Distortions resulting from both sawing and drying
is the lengthwise curvature of a piece of sawn timber caused by release of growth stress during sawing compared with warp which occurs during drying.

Dote: Early stages of decay in wood in which the color has changed but the strength and hardness have not yet been affected. Also called "incipient decay".

Dressed size (dimension): The dimensions of lumber after being surfaced with a planing machine.

Dressing: Running through a planer, surfacing.

Drybulb: A thermometer which measures the temperature of the air.

Drying schedule: A sequence of kiln conditions which result in a gradual decrease in moisture content of the wood.

Dry (timber): Seasoned, to a moisture content of 18 % or less. For hardwoods, usually seasoned to a moisture content of between 10-12%. Wood with a moisture content of less than 20% will not decay.

Dry rot: Any decay in wood in which the attack is confined to the cellulose and associated carbohydrates rather than the lignin, producing a light to dark brown friable residue. Also known as brown rot.

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Earlywood: The portion of the annual growth ring that is formed during the early part of the growing season.  It is usually a lighter colour, less dense, softer and weaker than latewood.

Edge: The narrow longitudinal surface usually at right angles to the face of a piece of timber.

Edger: A machine containing two or more circular saws used to square edge and/or rip slabs.

EMC: Equilibrium moisture content

End grain: 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).

End matched: Lumber that is end dressed and shaped to make a tongued-and-grooved joint at the ends when laid end to end.

Equalisation: The process of narrowing the moisture distribution between boards at the end of a drying charge.

Equilibrium moisture content (EMC): The moisture content at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature.

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Face: The wide longitudinal surface usually at right angles to the edge of a piece of timber.

Face cut: A cut made without using the saw bench's fence or sizing mechanism. An undimensioned cut which is used to produce a straight edge or face.

Feature: Distinctive natural and contrasting pattern inherent in timber.

Feller-buncher: A machine with a fixed-grip harvesting head which can grasp, cut, lift, swing and bunch trees for yarding. Usually this machine does not limb or crosscut to log lengths as a "cut-to-length" harvester can do.

Fence: A straightedge or linebar mounted parallel to the saw blade for guiding the lumber, cant, or flitch as it passes through the saw.

Fibre saturation point: The moisture content at which moisture is saturated within the cell walls of wood and the cell cavities are free of water.  Fibre-saturation point occurs at 25% MC to 32% MC depending on the species.  Below FSP water is held in wood as bound water within the cell cavities or lumen.

Fiddleback: Decorative wood figure caused by wavy grain pattern.

Fillet or Fillet-stick: Used for separating layers for drying. A wooden strip laid between each layer of lumber as it is stacked for drying.

Fine textured: Wood having small and closely spaced pores

Finger joint: An end joint in which wedge shaped projections in one piece of timber fit matching recesses on the other piece and are bonded together by an adhesive.

Fissile: Splits easily

Flat-sawn: Timber is flatsawn
Fully quartersawn and fully flatsawn boards
(or back-sawn) if the growth rings as seen from the end section meet the face of the board at an angle less than 45o with the board face.

Flitch: A large piece of sawn log intended for further cutting. A flitch may have two or more sawn edges but is not sawn to final dimension.

Flooring, overlay: Tongue- and-grooved flooring usually laid at 12mm thickness and glued to substrate such as concrete or particleboard.

Formaldehyde: A component of resin used to manufacture plywood and panel products, and a naturally occurring component of wood.

Forwarder: A vehicle with a cradle or trailer used to forward logs. Usually it is equipped with its own log loader device and may be tracked or wheeled.

Framing: The timber skeleton to which roofs, floors, and sides are attached.

Framing, light: The use of small cross-section members to provide support and enclosure for a building.

Free moisture: Moisture which is present in the cell cavities of wood.

Free of heart: Timber sawn to exclude the pith or heart center of the log.

Front end loader: A vehicle employed in the loading, unloading, stacking, or sorting of logs or materials.

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Glulam: Structural wood product made by bonding together laminations of dimensioned lumber.

Grade: The designation of the quality of a manufactured piece of wood. Classification of timber.

Grade-saw: Sawing for maximum recovery of high grade boards that are suitable for specialty uses.

Grain, cross: Fibres that deviate from a line parallel to the sides of the piece.

Grain: The general direction of the fibres or wood elements.

Grain, end: 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).

Grain, interlocked: Some fibres slope in a right-handed direction, and others in a left-handed direction.  Such wood is exceedingly difficult to split radially, though tangentially it may split fairly easily.

Grain, spiral: Fibers that take a spiral course around the trunk of a tree instead of the normal vertical course.  Causes sloping grain in timber.

Grain, straight: Fibres that run parallel to the axis of a piece.

Grain, wavy: Fibres that collectively take the form of waves or undulations.

Grain, woolly: Fraying of fibre in sawing or planing.

Grapple skidder: A skidder equipped with a grapple to handle logs.

Green size: The size that timber must be cut green to allow for sawing deviation, shrinkage in drying and further processing. 

Green timber: Freshly sawed or undried wood. Wood which has not been dried to 18% moisture or below.

Growth, old: Old, naturally established trees often characterized by dense straight grain and a lack of knots and defects.

Growth ring: One year’s growth increment of a tree composed of one band of earlywood and one band of latewood.

Growth stress: Stress developed in the wood of a standing tree. This can manifest as end-splitting soon after felling and distortion.

Gum pocket: A cavity which has contained, or continues to contain gum, resin or kino. Also called resin pocket.

Gum streak: Fibre saturated with gum, resin or kino. Also called gum vein or resin streak.

Gum vein: Fibre saturated with resin or kino. Also called gum streak.

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Hardwood: Wood from broadleaved trees.

Hazard classes:The hazard class
Hazard classes
H1.1 Timber used in situations protected from the
weather, dry in service and where resistance
to borer only is required.
H1.2 Timber used in situations protected from the
weather but where there is a risk of moisture
exposure conducive to decay.
H3.1 Timber used outdoors above ground,
exposed to the weather – generally in
non-structural applications; i.e. fascia
boards, weatherboards.
H3.2 Timber used outdoors above ground,
exposed to weather or protected from the
weather but with a risk of water entrapment;
i.e. decking, fencing and pergolas.
rating H1 to H6 tells you the level of treatment required to meet the durability provisions of Clause B2 of the New Zealand building code. Naturally durable timbers may meet these ratings without treatment.

Headrig: The first saw unit which performs the primary breakdown of the log.

Heart: also known as the corewood or inner heart, is the wood adjacent to and including the pith that is within 50 mm of the centre of the pith.

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.

Heartwood, pathological: Discoloured wood that is not true heartwood and with no natural durability.

Holes: A void in the timber.

Incipient decay: Early stages of decay in wood in which the color has changed but the strength and hardness have not yet been affected.

Indistinct: Not obviously different in appearance.

Intergrown knot: A sound or tight knot which has intergrown with the wood surrounding it. Bark or other voids are not visible on the surface of the wood and the knot is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.

Interlocked grain: Some fibres slope in a right-handed direction, and others in a left-handed direction.  Such wood is exceedingly difficult to split radially, though tangentially it may split fairly easily.

Internal check: A crack in the timber below the surface as a result of seasoning.

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Joinery: Finished timber fixtures of buildings such as doors, windows, panelling, cupboards, etc.

Joint, finger: An end joint in which wedge shaped projections in one piece of timber fit matching recesses on the other piece and are bonded together by an adhesive.

Juvenile wood: the first few years of growth around the pith.

Kaikaka: A form of decay occurring in standing totara. Kaikaka does not affect the durability of timber in service.

KAR: Knot area ratio. The area of the knot as a ratio of the area of the cross section of the timber. The proportion of cross section occupied by the projected area of the knot.

K.D.: Kiln dried.

Kerf: The width of the saw cut removed by the saw blade.

Kiln, conventional: is dried by controlling the moisture, temperature and air circulation. Heat is introduced via heat exchangers and warm humid air is removed via vents while cool dry air is introduced, usually at the other end of the kiln. Drying of hardwoods may require increased humidity such as introducing steam or water misting to slow the drying process.

Kiln, dehumidifier: A kiln working on the heat pump principle and evaporating moisture from the timber by a flow of warm air condensed on evaporator coils of a refrigeration unit and drained away. The refrigerant is compressed and passed through condenser coils, re-heating the air stream. Sometimes additional heat is applied in the early stages of drying.

Kiln-dry wood: Dried in a kiln with the use of artificial heat to a specified moisture content.

Kiln schedule: A stipulated set of dry- and wet-bulb temperatures and air velocities employed in drying a kiln charge.

Kino: A red gummy substance commonly found in eucalypts as either large pockets or in rings. 

Knot: That portion of a branch or limb that has been surrounded by subsequent growth of the stem.

Knot Area Ratio (KAR): The area of the knot as a ratio of the area of the cross section of the timber. The proportion of cross section occupied by the projected area of the knot.

Knot, bark-encased: A knot fully surrounded by bark as seen on the surface.

Knot, black: A knot whose colour is significantly darker than the surrounding timber. Can be either a tight intergrown knot or a loose knot

Knot, intergrown: A sound or tight knot which has intergrown with the wood surrounding it. Bark or other voids are not visible on the surface of the wood and the knot is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.

Knot, loose: A knot which is not firmly attached by wood or held in place, usually because it is fully bark encased. Like holes, effectively a void in the timber.

Knot, occluded: A knot which has partially healed over a stub which originated from pruning or branch breakage.

Knot, partially intergrown: A knot which has at least half its perimeter joined to the surrounding wood. 

Knot, pin: A sound intergrown knot not exceeding 15mm in diameter.

Knot, sound: A knot which has intergrown with the wood surrounding it and will thus not detach.

Knot, spike: Knot found on quartersawn timber, this knot is cut approximately parallel to the longitudinal axis so that the exposed section is elongated.

Knot, tight encased: A knot with more than half of its perimeter is loose (i.e. surrounded by bark) but which remains firmly in place.

Knothole: Opening produced when knots drop from the wood in which they were once embedded. Classed as a void.

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Laminated timber: An assembly made by bonding layers of veneer or lumber with an adhesive so that the grain of all laminations is essentially parallel.

Laminated veneer lumber: A structural lumber manufacture from veneers laminated into a panel with the grain of all veneer running parallel.

Latewood: The portion of the annual growth ring that is formed after the earlywood formation had ceased.  It is usually darker in colour, denser, harder and stronger than earlywood.

Length: Length of a piece of timber.

Lengths, random: Containing a variety of lengths.

Light framing: The use of small cross-section members to provide support and enclosure for a building.

Loader, front end: A vehicle employed in the loading, unloading, stacking, or sorting of logs or materials.

Log: A segment of a felled tree

Longitudinal: Oriented in the direction of the length of the wood grain.

Loose knot: A knots which is not firmly attached by wood or held in place, usually because it is fully bark encased. Like holes, effectively a void in the timber.

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.

Lumber recovery factor: Measurement of lumber recovery or yield from a quantity of log volume. A true measure of LRF is the finished shippable lumber per unit of logs delivered.

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Manufactured size: The dimensions for a given state of manufacture that are provided in product specifications.  Examples are rough-green, surfaced-dry, etc.

Matched, end: Lumber that is end dressed and shaped to make a tongued-and-grooved joint at the ends when laid end to end.

MC: Moisture content

Millwork: Woodwork, such as doors, window casings, and baseboards, ready-made.

Moisture content: The amount of water contained in the wood, either expressed as a percentage of the weight of the oven-dry wood or as a percentage of total weight of a piece.

Moisture content, equilibrium (EMC): The moisture content at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature.

Moisture content, target: The amount of moisture targeted to be left in the lumber at the end of kiln drying.

Moisture distribution: Variation in moisture content within a board and/or variation in moisture content between boards.

Moisture, free: Moisture which is present in the cell cavities of wood.

Moisture gradient: The difference in moisture content between areas of a board.  Usually refers to the moisture content difference between the surface and core of a board.

Nominal dimension (size): The size

Call sizes (mm) 25 40 50 75 100 125 150 200 225 250 300
Actual dressed dry size (mm) 19 35 45 70 90 115 140 180 205 230 280

by which timber is known and sold in the market; often differs from the actual size (e.g. 100x50 is actually dressed to 90x45). The named size which may vary from the actual size of the piece of wood because of variations due to sawing, shrinkage and dressing and the tolerances allowed for these operations. Also called call size.

 

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O.B.: The term appears ambiguous and with a range of definitions. "Outer Board" is a term used for rimu which includes sapwood. "Ordinary Board" refers to a lower grade of board from a packet from which the better grades selected already. "Off Bench" refers to timber which has been sawn and come directly off the saw bench, meaning rough sawn, green and ungraded. "Oversized Board" refers to the green rough sawn board being oversized to allow for shrinkage and dressing.

Occluded knot: A knot which has partially healed over a stub which originated from pruning or branch breakage.

Old growth: Old, naturally established trees often characterized by dense straight grain and a lack of knots and defects.

Oven-dry wood: Wood dried to a relatively constant weight in a ventilated oven at 102° to 105°C.

Oven-dry weight: Weight obtained by drying wood in an oven at 102° to 105°C until there is no more weight loss.

Overlay flooring: Tongue- and-grooved flooring usually laid at 12mm thickness and glued to substrate such as concrete or particleboard.

Over sized: A dimension greater than the nominal size which allows for shrinkage.

Partially intergrown knot: A knot which has at least half its perimeter joined to the surrounding wood. 

Particleboard: A generic term for a material manufactured from wood particles or other lignocellulosic material and a synthetic resin or suitable binder.

Pathological heartwood: Discoloured wood that is not true heartwood and with no natural durability.

Peel: To convert a log into veneer by rotary cutting.

Pin knot: A sound intergrown knot not exceeding 15mm in diameter.

Planer: Machine used to process rough lumber into a finished product, leaving it smooth and uniform in size. 

Planing allowance: The quantity of wood that is set to be removed by a planer during surfacing.

Pith: The small cylinder of primary tissue of a tree stem around which the annual rings form; the center of a tree. 

Pith-line: the absolute centre of the tree

Preservative: Any substance that, for a reasonable length of time, is effective in preventing the development and action of wood-rotting fungi, borers of various kinds, and harmful insects that deteriorate wood.

Product recovery: Product recovery: An expression of the amount of product (nominal or actual) that can be manufactured from a given input of raw material.

Pulp-logs: Logs of lesser value (e.g. smaller in diameter or with unacceptable defects) than sawlogs. Pulp logs are usually bought by the ton to be debarked, reduced to chips, and used to manufacture pulp and paper.

Punky: Wood which is beginning to decay and has softened.

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Quarter-sawn: Boards sawn
Fully quartersawn and fully flatsawn boards
so that the annual rings, as seen from the end-section, form an angle of not less than 45o with the board face.

Quarter-sawn, fully: When the growth rings
Fully quartersawn and fully flatsawn boards
as seen from the end-section show an angle not less than 80o to the face of the board. That is, boards cut with their faces parallel to the rays.

Radial surface: A longitudinal surface or plane extending wholly or in part from the pith to the bark.

Random lengths: Lumber containing a variety of lengths.

Rays: A ribbon-like aggregate of wood cells extending radially across the grain, radiating out from the pith to the bark.

Reaction wood: Reaction wood results from a lean in the stem and is abnormal cell growth. In softwoods, it is known as compression wood, and in hardwoods it is
called tension wood.

Reconditioning: A process for relieving the stresses present in wood at the end of drying.

Recovery factor, lumber: Measurement of lumber recovery or yield from a quantity of log volume. A true measure of LRF is the finished shippable lumber per unit of logs delivered.

Recovery, product: Product recovery: An expression of the amount of product (nominal or actual) that can be manufactured from a given input of raw material.

Resaw: Machines after the headrig for resawing flitches, cants, slabs and roundbacks. May be a breastbench, and edger or a band saw.

Resawing: The process of sawing lumber in two lengthwise, parallel to the wide face. It is usually, though not always, done through the middle of the board, producing two equal sized boards, each approximately half the thickness of the original. Resawing changes the thickness of the lumber but not its width.

Resin pocket: A cavity which has contained, or continues to contain gum, resin or kino. Also called gum pocket.

Resin streak: Fibre saturated with gum, resin or kino. Also called gum vein or gum streak.

Resourcinol: An adhesive made from resorcinol resin and formaldehyde.

Rift-sawn: Timber is rift-sawn if the growth rings as seen from the end section meet either face of the board at an angle of both less than 45o and more than 45o. That is, the board is partially quarter-sawn and partially flat-sawn.

Rip: To cut a board lengthwise, parallel to the fibers.

Ripping: Sawing or cutting with the grain as with a rip saw.

Rough-sawn: timber that has not been dressed (surfaced) but which has been sawed.

Rotary-cut veneer: Veneer cut from a log which is centered in large lathe. As the log revolves, the cutting knife moves toward the center and a continuous sheet of veneer is peeled from the log.

Rot, butt: Decay or rot characteristically confined to the base or lower bole of a tree.

Rot, dry: Any decay in wood in which the attack is confined to the cellulose and associated carbohydrates rather than the lignin, producing a light to dark brown friable residue. Also known as brown rot.

Rot, white: Decay attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy.

Roundback: A piece of timber from the outside of the log with only one flat, sawn face.

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Sap stain: A bluish or dim-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. Decay or softening of the wood has not taken place.

Sarking: A timber or felt cladding placed over rafters before the roof is fixed in place.

Sapwood: The outer layers of a tree stem that contain living cells.  The sapwood is often lighter in colour than heartwood. Sapwood is not naturally durable as it does not contain extractives.

Saturation point, fibre (FSP): The moisture content at which moisture is saturated within the cell walls of wood and the cell cavities are free of water.  This averages around 20 % moisture content.  Below FSP water is held in wood as bound water within the cell cavities or lumen.

Sawlog: A log suitable for producing sawn lumber.

Sawing deviation: The deviation from target sawn sizes resulting from sawing.

Sawmill, band: An evolution in sawmill technology that uses a thinner band saw blade (less kerf therefore less sawdust waste) than a circular saw.

Sawmill, circular: The traditional sawmill uses a circular saw. Circular saws are thicker (larger kerf) than band saws and produce more waste (sawdust). 

Schedule, drying: A sequence of kiln conditions which result in a gradual decrease in moisture content of the wood.

Schedule, kiln: A stipulated set of dry- and wet-bulb temperatures and air velocities employed in drying a kiln charge.

Seasoned timber: Timber that has been dried.

Seasoning: Drying timber to a moisture content appropriate to the conditions and purposes for which it is to be used.

Seconds: Lower quality boards.

SED: Small end diameter.

Shakes:

  1. Breakage or longitudinal separation of wood fibres due to causes other than drying, usually originating in the log or tree. Also called "compression fractures", "brittle heart", or "thunder-shakes" (when resulting from felling).
  2. A roofing or sidewall product made by splitting blocks of wood.

Shingles: A roofing or sidewall product used like tiles and made by sawing wood into small rectangular pieces tapering in thickness.

Shook: Small length of timber suitable for finger-jointing.

Shorts: Short pieces of sawn timber.

Shrinkage: Shrinkage
Radial shrinkage is greater than tangental
is the contraction of wood to water loss below fiber saturation point.  Expressed as a percentage of the green dimension.

Size, actual: The dimensions obtained when an individual piece of lumber is measured with a caliper and tape.

Size, dressed: The dimensions of lumber after being surfaced with a planing machine.

Size, green: The size that timber must be cut green to allow for sawing deviation, shrinkage in drying and further processing. 

Size, manufactured: The dimensions for a given state of manufacture that are provided in product specifications.  Examples are rough-green, surfaced-dry, etc.

Size, nominal: The size in name only; the commercial name by which lumber is known and sold on the market (e.g., 100x50) and the basis used to calculate lumber volume.

Size, target: The size that lumber must be cut in the green form to allow for sawing deviation, shrinkage in drying and allowance for fibre removed in the finishing process.

Skidder: Usually a wheeled vehicle, used for sliding/dragging logs from the stump to the landing.

Skidder, grapple: A skidder equipped with a grapple to handle logs.

Skip: An area that failed to dress.

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Skip dress: To put a rough sawn piece of timber through a thicknesser or four-sider once in order to prepare for a second final pass for final dimensioning.

Slab: Timber which has been dimensioned to thickness but not width
Slabs can also be bark to bark
.

Slabwood: waste wood resulting from sawmilling.

Sliced veneer: Veneer sliced from a cant with knives. Sliced veneer can be quartersawn, giving it a different appearance from rotary peeled veneer.

Sloping grain: The fibres are arranged at an angle to the edge or face of the sawn timber. These fibres can be difficult to make out visually and are not necessarily indicated by growth-ring direction. Both the face and edge of the timber needs to be studied carefully and where necessary the slope of the grain determined with a swivel handled scribe. The slope should be measured over a reasonable distance to determine the general slope. Slope deviations on only part of the surface can be disregarded. Intergrown spike knots can weaken timber because of sloping grain.

Soft rot: A special type of decay that develops in the outer wood layers under very wet conditions, such as in cooling towers and boat timbers. It is caused by micro-fungi that attack the secondary cell walls (and not the intercellular layer) and destroy its cellulose content.

Softwood: Wood from conifer trees

Sound knot: A knot which has intergrown with the wood surrounding it and will thus not detach.

Specialty timber: Higher-value species used for specialty purposes. Species with individual properties or qualities which are greater than radiata pine.

Spalting: Discoloration, prominent black lines and changes in texture that occur during the initial decay process of wood. Wood captured between being sound and rotten, before the cellular structure of the wood deteriorates

Species: Type of wood.

Spike-knot: Knot found on quartersawn timber, this knot is cut approximately parallel to the longitudinal axis so that the exposed section is elongated. Seen on the face of the timber as a branch cut longitudinally, extending from one edge towards the other. Can be intergrown, partially occluded or occluded and is characterised by surrounding sloping grain.

Spiral-grain: Fibers that take a spiral course around the trunk of a tree instead of the normal vertical course.  Causes sloping grain in timber.

Split: A lengthwise separation of fibres extending right through a piece of timber from one surface to another.

Spring: Also known as crook. The lengthwise curvature of the edge of a piece of sawn timber.

Stain: Discolouration that varies and is in contrast to the natural colour of the timber.

Stain, sap: A bluish or dim-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. Decay or softening of the wood has not taken place.

Standing timber: Timber not yet felled, remaining on the stump.

Sticker: Fillet.

Straight-grain: Fibres that run parallel to the axis of a piece.

Stress, growth: Stress developed in the wood of a standing tree. This can manifest as end-splitting soon after felling and distortion.

Strip floor: A tongue and groove floor laid over joists.

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.

Stumpage: The value of timber as it stands uncut in the woods. The residual value after all logging costs are taken from the delivered price of logs at the mill yard.

Surface check: A visible crack on the surface of the timber resulting from seasoning.

Surface, radial: A longitudinal surface or plane extending wholly or in part from the pith to the bark.

Surface, tangental: A longitudinal surface which is tangential or perpendicular to the radius.  Flat-sawn lumber is sawn tangentially.

Surfacing: running through a planer, dressing.

Sweep: Curvature along the full length of a log.

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Tangental section: A tangential section is a longitudinal section through a tree, perpendicular to a radius.  Flat-sawn lumber is sawn tangentially.

Taper-sawing: Sawing by making cuts parallel to the outside surface (i.e., bark) rather than parallel to the longitudinal axis (i.e., pith).

Target moisture content: The amount of moisture targeted to be left in the lumber at the end of kiln drying.

Target size: The size that lumber must be cut in the green form to allow for sawing deviation, shrinkage in drying and allowance for fibre removed in the finishing process.

Tension wood: Abnormal wood found in leaning trees of hardwoods and characterized by the presence of gelatinous fibers and excessive longitudinal shrinkage.  Tension wood fibers hold together tenaciously, so that the sawed surfaces usually have projecting fibers, and planed surfaces often are torn or have raised grain.  Tension wood may cause warping.

Textured, coarse: Wood with large pores.

Textured, fine: Wood having small and closely spaced pores

Tight encased knot: A knot with more than half of its perimeter is loose (i.e. surrounded by bark) but which remains firmly in place.

Tight knot: A knot which is firmly held in place with wood fibres.

Thickness: Unless otherwise specified, the call dimension of the thickness of the piece of timber.

Timber, standing: Timber not yet felled, remaining on the stump.

Tongue and groove: Lumber machined to have a groove on one side and a protruding tongue on the other, so that pieces will fit snugly together, with the tongue of one fitting into the groove of the other.

Truss: A triangular arrangement of structural members.

Twist: A spiral distortion along the length of the timber.

T & G: Tongue and groove profile.

T G & V: Tongue, groove and V profile used for panelling.

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Veneer: A thin layer or sheet of wood.

Veneer, rotary-cut: Veneer cut from a log which is centered in large lathe. As the log revolves, the cutting knife moves toward the center and a continuous sheet of veneer is peeled from the log.

Veneer, sawed: Produced by sawing.

Veneer, sliced: Veneer sliced from a cant with knives. Sliced veneer can be quartersawn, giving it a different appearance from rotary peeled veneer.

Void: A gap or hole in the surface devoid of timber. A loose knot, hole, or small area of decay can be classed as a void.

Wane: The absence of square wood on the edge of a board indicated by the underbark surface.

Wane allowance: The maximum percentage of wane that can be left on the edge of a cut board.

Want: The absence of wood, other than wane, from the arris or surface of a piece of timber.

Warp: Any deviation from a true or plane surface in a board. Examples are bow, crook, cup or twist, or a combination of these.

Wavy-grain: Fibres that collectively take the form of waves or undulations.

Wetbulb: A drybulb with a wet sock pulled over it to measure the cooling effect of moisture evaporation from its surface.  Used to monitor and maintain humidity conditions within a conventional kiln.

Width: Unless otherwise specified, the call dimension of the width of the piece of timber.

Wood: A solid lignocellulosic material naturally produced in trees and some shrubs, made of up to 40%-50% cellulose, 20%-30% hemicellulose, and 20% -30% lignin.

Wood density: The mass of wood substance having unit volume.  Expressed as kilograms per cubic metre at a specified moisture content.

Woolly grain: Fraying of fibre in sawing or planing.

White rot: Decay attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy.
 

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