Acclimation – The act of allowing wood moisture content to become at equilibrium with the environment in which it will perform.

Airdried – The dried condition of lumber, usually 12 to 20 percent moisture content, reached by exposing the wood for a sufficient period to the prevailing atmospheric con­ditions.

Air Drying – The process of drying green lumber by exposure to prevailing atmospheric conditions.

Annual Growth Ring – The growth layer added to the tree each year in temperate climates, or each growing season in other climates; each ring includes springwood and summer- wood.


Bark – Outer layer of a tree, which consists of a thin, living inner part and a dry, dead outer part that is generally resistant to moisture movement.

Beveled Edge (Micro Bevel) – The chamfered or beveled edge of wood flooring, plank, block and parquet.

Bleeding – When the color of a stain or other coating material works up into succeeding coats, imparting to them a certain amount of color, it is said to bleed.

Blistering – The formation of bubbles or pimples on the surface of finished work. It is caused by exposure to excessive heat, grease, or other volatile material in the finish, by moisture in the wood, or by too frequent application of coats. Anything that causes a gas or vapor under the film may cause blistering.

Board –  (1) Yard lumber that is less than 2 inches (50 mm) thick and 2 or more inches wide. (2) A term usually applied to 1-inch- (25.4-mm-) thick lumber of all widths and lengths.

Burl – A swirl or twist of the grain of the wood that usually occurs near a knot, but doesn’t contain a knot, commonly found in the stump of a tree and where limbs branch out from the tree.


Cambium – The one-cell-thick layer of tissue between the bark and wood that repeatedly subdivides to form new wood and bark cells.

Cell – In wood anatomy, a general term for the minute units of wood structure having distinct cell walls and cell cavities.

Check – (Syn: Cracks, drying check, checking) A separation of the wood fibers within or on a log, timber, lumber, or other wood product resulting from tension stresses set up during drying, (usually the early stages of drying).

Clear Wood – Wood without knots.

Color Change – Visual changes in the color of the wood species caused by exposure to light, deprivation of light and air, or some chemical reaction.

Cross Section – (Syn: Transverse section) A section of a board or log taken at right angles to the grain.

Crowning – A convex or crowned condition or appearance of individual strips with the center of the strip higher than the edges, the opposite of cupping.

Cupping – A form of board warp in which there is a deviation from a straight line across the width.  Direction of warp distinguished by a “smile or frown” cup

Cure – To change the properties of an adhesive by chemical reaction (which may be condensation, polymerization or vulcanization) and thereby develop maximum strength. It is generally accomplished by the action of heat or a catalyst, with or without pressure.


Decay – (Syn: Rot, dote) The decomposition of wood substance by fungi. In advanced (or typical) decay, 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. Early (or incipient) decay refers to the stage at which the decay has not proceeded far enough to soften or otherwise perceptibly impair the hardness of the wood. Early decay is usually accompanied by a slight discoloration or bleaching of the wood.

Defect – An irregularity or imperfection in a tree, log, bolt, or lumber that reduces its volume or quality or lowers its durability, strength, or utility value. Defects may result from knots and other growth conditions and abnormalities; from insect or fungus attack; and from milling, drying, machining, or other processing procedures.

Delamination – The separation of layers in an engineered wood floor, through failure within the adhesives or between piles. Also between layers of stain and/or coating.

Density – The weight of a body per unit volume, usually expressed in pounds per cubic foot (grams per cubic centimeter). In wood, density changes in terms of moisture content.

Diffuse Porous Wood—A hardwood 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.

Discoloration – (Syn: Stain) Change in the color of lumber resulting from fungal and chemical stains, weathering, or heat treatment.

Distressed – A heavy artificial texture in which the floor has been scraped, scratched or gouged to give it a time-worn antique look.

Dry Kiln – A room, chamber, or tunnel in which the temperature and relative humidity of air circulated through parcels of lumber and veneer govern drying conditions.

Drying – The process of removing moisture from wood to improve its serviceability in use.

Drying or Kiln Schedule – The prescribed schedule of dry-bulb temperature and wet-bulb temperature or relative humidity used in drying; sometimes expressed in terms of wet- bulb depression or equilibrium moisture content (EMC). In kiln drying, air velocity isan important aspect.


Earlywood – (Syn: Springwood) Wood formed during the early period of annual growth; usually less dense and mechanically weaker than wood formed later.

End Grain – The ends of wood pieces that are cut perpendicular to the fiber direction. Flat grain—Syn: Flat sawn, plain grain, plain sawn, tangential cut. Lumber sawn or split in a plane approximately perpendicular to the radius of the log. Lumber is considered flat grained when the annual growth rings make an angle of less than 45′ with the surface of the piece.

End-Matched – In tongue and groove strip and plank flooring, the individual pieces have a tongue milled on one end and a grooved milled on the opposite end, so that when the individual strips or planks are butted together, the tongue of one piece fits in the groove of the next piece.

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 substances.


Fiber Wood – A comparatively long, narrow, tapering hardwood 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.

Fire Retardant – A chemical or preparation of chemicals used to reduce flammability or to retard the spread of a fire over a surface.

Flatsawn – Lumber sawed in a plane approximately perpendicular to a radius of the log. See Grain.

Floating Floor – A floor that does not need to be nailed or glued to the subfloor. Typically the flooring panels are connected together by adhesive or mechanical connectors.

Fungi – Low forms of plants consisting mostly of microscopic threads that traverse wood in all directions, converting the wood to materials the plants use for their own growth. Fungi cause decay and staining of lumber.

Fungicide – A chemical that is toxic to fungi.


Grade – A classification or designation of the quality of manufactured pieces of wood or of logs and trees.

Grain – The direction, size, arrangement, appearance, or quality of the fibers in lumber. When used with qualifying adjectives, the term designates the orientation of fibers and/or growth rings in lumber.

Green Lumber – (1) In general, lumber just as cut from freshly felled trees. (2) In accor­dance with the American Softwood Lumber Standard, lumber above 19 percent mois­ture content.

Growth Ring – A layer of wood (as an annual ring) produced during a single period of growth.

Growth Rate – The rate at which a tree has laid on wood, measured radially in the tree trunk or in the radial direction in lumber. The unit of measure in use is the number of annual growth rings per inch.


Hardwood – Generally, one of the botanical groups of trees that have broad leaves-—e.g. oak, elm, basswood—in contrast to the conifers or softwoods. Also, the wood produced from such trees. (The term has no reference to the actual hardness of the wood.)

Heartwood – The inner layers of wood in growing trees that have ceased to contain living cells and in which the reserve materials, e.g., starch, have been removed or converted into resinous substances. Heartwood is generally darker than sapwood, although the two are not always clearly differentiated.


Infestation – The establishment of insects or other animals in wood.


Juvenile Wood – The initial wood formed adjacent to the pith, often characterized by lower specific gravity, lower strength, higher longitudinal shrinkage, and different micro­structure than that of mature wood.


Kiln – A chamber or tunnel used for drying and conditioning lumber, veneer, and other
wood products in which the temperature and relative humidity are controlled.

Kiln Drying – The process of drying lumber in a closed chamber in which the temperature and relative humidity of the circulated air can be controlled.

Knot – That portion of a branch or limb that has been surrounded by subsequent growth of the wood of the trunk or other portions of the tree. A knot hole is merely a section of the entire knot, its shape depending upon the direction of the cut.


Latewood – (Syn: Summerwood) The portion of the annual growth ring that is formed after the earlywood formation has ceased. Latewood is usually denser and mechanically stronger than earlywood.

Lumber – The product of the sawmill and planing mill not further manufactured except by sawing, resawing, passing lengthwise through a standard planing machine, cross cut­ting to length, and matching.


Mineral Streak – An olive to greenish-black or brown discoloration of undetermined cause in hardwoods, particularly hard maples; commonly associated with bird pecks and other injuries; occurs in streaks usually containing accumulations of mineral matter.

Moisture Content – Weight of water contained in the wood, expressed as a per­centage of the weight of the ovendry wood.

Mold – A fungus growth on lumber at or near the surface and, therefore, not typically re­sulting in deep discolorations.


Old Growth – Timber in or from a mature, naturally established forest. When the trees have grown during most, if not all, of their lives in active competition with other trees for sunlight and moisture, the timber is usually straight and relatively free of knots.


Parquet – A patterned floor.

Partly Airdried – Wood with an average moisture content between 25 and 45 percent, with no material over 50 percent.

Pin Knot – A knot that is less than 1/2″ in diameter

Pith – The small, soft core at the original center of a tree around which the wood forms. Plainsawn—Another term for flatsawn or flatgrained lumber.

Pore – The cross section of a specialized hardwood cell known as a vessel. 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.


Quartersawn – Another term for edge-grained lumber, showing the radial surface of the wood.


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

Relative Humidity – The amount of water vapor in the atmosphere, expressed as a per­centage of the maximum quantity that the atmosphere could hold at a given tempera­ture. The amount of water vapor that can be held in the atmosphere increases with thetemperature.

Resin Canal (or duct) – An inter-cellular passage that contains and transmits resinous materials. Resin canals extend vertically or radially in a tree.

Ring-Porous Wood – Wood in which the pores of the earlywood (springwood) are dis­tinctly larger than those of the latewood (summerwood) and form a well-defined zone or growth ring.

Rot – Decay.


S4S (Surface-4-Sides) – Flooring that isn’t tongue and grooved. May also refer to square-edge strip flooring that is face nailed when installed.

Sap – The moisture in green wood, containing nutrients and other chemicals in solution.

Sapwood – The outer zone of wood in a tree, next to the bark. In a living tree, sapwood contains some living cells (the heartwood contains none), as well as dead and dying cells. In most species, it is lighter colored than the heartwood. In all species, it lacks resistance to decay.

Season – To dry lumber and other wood items to the desired final moisture content and stress condition for their intended use.

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.

Shrinkage – The contraction of wood fibers caused by drying below the fiber saturation point. Shrinkage (radial, tangential, and volumetric) is usually expressed as a percent­age of the dimension of the wood when green.

Softwood – Generally, one of the botanical groups of trees that, in most cases, have nee­dlelike to scalelike leaves; the conifers. Also, the wood produced by such trees. (The term has no reference to the actual hardness of the wood.)

Sound Knot – (Syn: Tight Knot) A knot in a piece of lumber that is firmly fixed, undecayed and as strong as the surrounding wood.

Species – A group of individual plants of a particular kind; that is, a group of individuals sharing many of the same characteristics. Species is lower in classification than the genus, but higher than the variety.

Specific Gravity – The ratio of the ovendry weight of a piece of wood to the weight of an equal volume of water at 39°F (4°C). Specific gravity of wood is usually based on the green volume and ovendry weight.

Springwood – See Earlywood.

Square Edge – Flooring that abuts without a broken plane.

Stain – A discoloration in wood that may be caused by micro-organisms, metal, or chemi­cals. The term also applies to materials used to impart color to wood.

Straight Grain – Lumber in which the fibers and other longitudinal elements run paral­lel to the axis of a piece.

Strength – The term in its broad 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.

Stress – Force per unit of area.

Summerwood – See Latewood.

Swelling – Increase in the dimensions of wood caused by increased moisture content. Swel­ling occurs tangentially, radially, and, to a less extent, longitudinally.


Tangential – Strictly, coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent. In practice, however, tangential 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 plainsawn lumber is sawn tan­gentially.

Tension Wood – A type of wood found in leaning trees of some hardwood species, charac­terized by the presence of fibers technically known as “gelatinous” and by excessive longitudinal shrinkage. Tension wood fibers tend to “pull out” on sawn and planed sur­faces, giving so-called fuzzy grain. Tension wood causes crook and bow and may collapse. Because of slower than normal drying, tension wood zones may remain wet when the surrounding wood is dry.

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.

Trim – The flooring materials in a building at the floor of rooms, (baseboard, base shoe, quarter-round for example)

Tylose – 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 axial tracheids.


Unfinished – A product without stain or finish.


Vessels – Wood cells in hardwoods 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.


Warp – Distortion in lumber causing departure from its original plane, usually developed during drying. Warp includes cup, bow, crook, twist, and kinks or any combination thereof.

Weathering – The mechanical or chemical disintegration and discoloration of the surface of lumber that is caused by exposure, light, the action of dust and sand carried by winds, and the alternate shrinking and swelling of the surface fibers with continual variation in moisture content brought by changes in the atmosphere. Weathering does not in­clude decay.

Whip Saw – Any saw with a flexible blade, such as a band saw.

Whip Sawn ™ Flooring a look derived from the reciprocal action of a whip saw or pit saw.  In the early days, before the availability of power machines, a pit saw operation of one man above and the other in a pit was used to saw logs. It was a challenge for the pit boss to control the wobble of the flexible blade, therefore undulation and saw marks resulted and required a secondary craftsman to smooth out the surface.  Now, due to the popularity of vintage and the woof and warp of early Americana, Heppner Hardwoods has created this same texture through proprietary processes.

Wood – (Syn: Xylem) The tissues of the stem, branches, and roots of a woody plant lying between the pith and cambium, serving for water conduction, mechanical strength, and food storage, and characterized by the presence of tracheids or vessels.

Wood Reaction – In wood anatomy, wood with more or less distinctive anatomical char­acteristics; formed in parts of leaning or crooked stems and, branches. Reaction wood consists of tension wood in hardwoods and compression wood in softwoods.

Workability – The degree of ease and smoothness of cut obtainable with hand or machine tools.