Key hardwood flooring terms

Lets start with the basics.   

Width - This refers to the width of the face of the board (side to side).  Typical widths range from 2 1/4" to 8".   The most common widths are 3 1/4" and 5".Terms

Lengths - Lengths is the measurement of the entire length of the board.  Most prefinished hardwood flooring is random length with an overall average.  As a general rule, most solid prefinished hardwood flooring lengths are between 1' to 7' with an average length of 3.5'.

Thickness -Thickness is the measurement of "height" of the board.  Most common thickness is 3/4" however other thicknesses are available.  


Types of edge construction

Square Edge - This type of construction has the edges of the board meeting flush without any type of recess or bevel.   Creates a look of traditional site finished floors. 

Microbeveled Edge -  This type of construction cuts a very small bevel on the edge of the plank.   It creates definition between planks.  Used extensively with prefinished flooring.   This construction also helps eliminate with "over wood" where one plank might be sightly higher then the other plank.  

 Types of Subfloor.  

As the old saying goes, you are only as good as your foundation.   This is true with prefinished hardwood flooring, as well.   Lets look at the types of subfloors.  

Plywood - This is an engineered stranded product that has glue as a bonding agent.   Layers alternate in different directions for strength and rigidity.   It will not typically warp or shrink.   Plywood is laid over your floor joist and is a great subfloor for prefinished hardwood flooring.  

OSB (Orient Strand Board) - Similar to plywood contruction, the difference is the particals of wood are narrow strands.  Again, as with plywood, the layers alternate for strength and rigidity.  OSB is a suitable subfloor for prefinished hardwood flooring.  

Partical Board - Made from small wood chips and saw dust bonded together with glue.  This subfloor is cheaper and less durable then OSB or Plywood.  

 Grade- Grade refers to the floor of your house and if it is above ground level or below.   For example a basement is considered "below grade" and the middle and top floor are considered "above grade"   The key is to realize that below grade floors can be susceptable to moisture issues and this should be considered when purchasing your floor.  A graphic will let you know if the flooring you are considering is appropriate for your application.    

All the Terms! 



Abrasion Resistance That property of a surface that resists being worn away by a rubbing or friction process. Abrasion resistance isn't necessarily related to hardness, as believed by some, but is more closely comparable to, or can be correlated with, toughness.

Acclimation The act of allowing wood moisture content to become at equilibrium with the environment in which it will perform. (See EMC, Equilibrium Moisture Content)

Acid Chemical substance rated below 7 on the PH scale.

Air-Dried Dried by exposure to air in a yard or shed without artificial heat. (Not kiln dried)

Alkalinity A measurement of an alkaline rating about 7 on the PH scale.

Annual Growth Ring The layer of wood growth formed on a tree during a single growing season.

Asphalt Saturated Felt Paper A #15 asphalt felt paper that meets ASTM Standard D-4869 or asphalt laminated paper that meets federal specification UU-B-790a Grade B, Type I, Style 1a, or asphalt saturated paper that meets federal specification UU-B-790a, Grade D, Type I, Style 2. Commonly used as a vapor retarder.

ASTM (American Society for Testing and Materials) develops and publishes voluntary technical standards for a wide range of materials, products, systems, and services. ASTM uses a consensus process involving technical committees that draw their members from around the world. ASTM International has no role in requiring or enforcing compliance with its standards, but in many instances its standards have been adopted by rules-making industry and governmental bodies.

ASTM F-2170 Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ Probes.

ASTM F-1869 Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.

ASTM (modified) D-4944-043. Calcium Carbide (CM) Test.

Base Shoe A molding designed to be attached to baseboard molding to cover expansion space. It is the alternative to a quarter-round in profile.

Bastard Sawn See Rift Sawn.

Beveled Edge The chamfered or beveled edge of wood flooring, plank, block and parquet.

Board Foot A unit of measurement of lumber represented by a board 1 foot long, 12 inches wide and 1 inch thick or its cubic equivalent. In practice, the board foot calculation for lumber 1 inch or more in thickness is based on its nominal thickness and width and the actual length. Lumber with a nominal thickness of less than 1 inch is calculated as 1 inch.

Borders Simple or intricate designs which frame and customize a flooring installation.

Bow The distortion of lumber in which there is a deviation, in a direction perpendicular to the flat face, from a straight line from end to end of the piece.

Burl 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.

Chatter Marks Slight, closely spaced indentations causing a ripple effect on the surface of a wood floor.

Check A lengthwise separation of the wood that usually extends across the rings of annual growth.

Checking (finish) Similar to alligatoring, except that the finish is broken into smaller segments.

Cleat A barbed fastener commonly used as a mechanical device to fasten hardwood flooring.

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.

Compression Set Caused when wood strips or parquet slats absorb excess moisture and expand so much that the cells along the edges of adjoining pieces in the floor are crushed. This causes them to lose resiliency and creates cracks when the floor returns to its normal moisture content.

Coniferous See Softwoods.

Crook The distortion of a board in which there is a deviation, in a direction perpendicular to the edge, from a straight line from end to end of the piece.

Cross Directed Laying of material perpendicular to the material below it.

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 concave or dished appearance of individual strips with the edges raised above the center. The opposite of crowning.

Deciduous See Hardwoods.

Deformed fasteners Fastener in which the sides are not smooth and the head shape may be irregular. Examples are ring-shank and screw-shank nails.

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

Diffuse-Porous Woods 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 annual growth ring. Hard maple is an example.

Dimensional Stability The ability to maintain the original intended dimensions when influenced by a foreign substance. Wood is hygroscopic (readily takes up moisture) and isn't dimensionally stable with changes in moisture content below the fiber saturation point. Engineered wood flooring, however, is more dimensionally stable than solid wood.

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

Drywall Interior covering material (such as gypsum board, hardboard or plywood) that is applied in large sheets or panels.

Durability The ability of the wood species or finish to withstand the conditions or destructive agents with which it comes in contact in actual usage, without an appreciable change in appearance or other important properties.

Eased Edge See Beveled Edge.

End Joint The place where two pieces of flooring are joined together end to end.

End Lifting A swelling of the top layer of engineered wood flooring, occurring at an end joint.

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

Engineered An assembly made by bonding layers of veneer or lumber with an adhesive so that most adjacent layers have their grains going in perpendicular directions to increase dimensional stability.

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.

Fading The loss of color due to exposure to light, heat or other destructive agents.

Feature Strip A strip of wood used at a threshold or to border a room or to otherwise serve as an accent. Usually of a contrasting color or species.

Fiberboard A broad generic term inclusive of sheet materials of widely varying densities manufactured of refined or partially refined wood or other vegetable fibers. Bonding agents and
other materials may be added to increase strength, resistance to moisture, fire or decay, or to improve some other property.

Fiber Saturation Point The stage in drying or wetting wood at which the cell walls are saturated with water and the cell cavities are free from water. It's usually taken as approximately 30 percent moisture content, based on over-dry weight.

Figure Inherent markings, designs or configurations on the surface of the wood produced by the annual growth rings, rays, knots and deviations from regular grain.

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. Wood filler used for cracks, knotholes and worm holes is often a commercial putty, plastic wood or other material mixed to the consistency of putty. A wood filler also may be mixed on the job using sanding dust from the final sanding, or other suitable material, mixed with a product appropriate for this use.

Fillets The small components that comprise finger-block parquet. Also called fingers or slats. Fillet may also refer to the top layer of some engineered wood flooring.

Fingers See Fillets.

Finger-block Parquet made from small strips of wood assembled together. See Fillets.

Fire Resistance The property of a material or assembly to withstand fire or given protection from it. Certain species naturally provide greater fire resistance than others. Classes are I-II-III or A-BC with Class I or A being the most fire resistant.

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

Flag A heavy dark mineral streak shaped like a banner.

Flag Worm Hole One or more worm holes surrounded by a mineral streak.

Flame Spread The propagation of a flame away from the source of ignition across the surface of a liquid or solid, or through the volume of a gaseous mixture. NOTE: Most wood species are Class C Flame Spread unless the wood floor has been treated and marked as to flame spread.

Flecks The wide irregular, conspicuous figure in quartersawn oak flooring. See Medullary Rays.

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.

Flow The characteristic of a coating that allows it to level or spread into a smooth film of uniform thickness before hardening.

Graininess The objectionable appearance of small, grain-like particles in a finishing material or in the dried film thereof.

Hardened Steel Pin Specialty fasteners designed to penetrate and hold concrete, steel and other substrates. Steel pins are typically installed with powder, pneumatic or gas-powered tools.”

Hardness That property of the wood species or dried film of finishing material that causes it to withstand denting or being marked when pressure is exerted on its surface by an outside object or force.

Hardwood Generally, one of the botanical groups of deciduous 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 a tree. It is usually darker than sapwood. See Pith and Sapwood.

Heavy Streaks Spots and streaks of sufficient size and density to severely mar the appearance of wood.

Honeycombing Checks often not visible at the surface that occur in the interior of a piece of wood, usually along the wood rays.

Humidity The amount of water vapor in the air. See Relative Humidity.

Hygrometer An instrument for measuring the degree of humidity or relative humidity of the atmosphere.

Hygroscopic A substance that can absorb and retain moisture, or lose or throw off moisture. Wood and wood products are hygroscopic. They expand with absorption of moisture and their dimensions become smaller when moisture is lost or thrown off.

In Situ A Latin term that means “in place” or “on site,” the term applies to testing done on site, or on materials in their original location, as opposed to testing done in a laboratory. Some sound- control testing is done in the field or “in situ,” and moisture testing of concrete slabs is often done using “in situ” probes.

Intensity The intensity of a color is its purity or degree of hue as seen by the eye.

Jointed Flooring Strip flooring, generally birch, beech, hard maple or pecan, manufactured with square edges, not side-matched, but usually end-matched. It is used principally for factory floors where the square edges make replacement of strips easier.

Joist One of a series of parallel beams used to support floor or ceiling loads and supported in turn by larger beams, girders or bearing walls.

Kiln (often pronounced "kill") A chamber having controlled air flow, temperature and relative humidity for drying lumber, veneer and other wood products.

Kiln-Dried Dried in a kiln with the use of artificial heat.

Knot The 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. In hardwood strip flooring, small and pin knots aren't more than one-half inch in diameter. A sound knot is a knot cut approximately parallel to its long axis so that the exposed section is definitely elongated.

Manufacturing Defects Includes all defects or blemishes that are produced in manufacturing, such as chipped grain, torn grain, skips in dressing, hit-and-miss (a series of surfaced areas with skips between them), variation in machining, machine burn, and mismatching.

Mechanic A flooring installer, sander or finisher.

Medullary Rays Strips of cells extending radially within a tree and varying in height from a few cells in some species to four 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. See Flecks.

Mineral Spirits A solvent product used as a thinner and/or cleaner.

Mineral Streak Wood containing an accumulations of mineral matter introduced by sap flow, causing an unnatural color ranging from greenish brown to black.

Mixed Media A wood floor that is predominately of wood, but also incorporates other materials, such as slate, stone, ceramic, marble or metal.

Moisture Content the amount of moisture in wood expressed as a percentage of the weight of oven-dried wood. National Oak Flooring Manufacturers Association hardwood flooring is manufactured at 6 to 9 percent moisture content, with a 5 percent allowance for pieces up to 12 percent moisture content. Five percent of the flooring may be outside of this range.

Muratic Acid A diluted acid used to neutralize alkalinity of concrete subfloors.

Nailing Shoe (or Nailing Plate) An attachment to a blind-nailing machine that broadens the impact area. Often required for fastening factory-finished flooring.

Nominal Size As applied to timber or lumber, the size by which it is known and sold in the market; often different from actual size.

Nosing A hardwood molding used to cover the outside corner of a step, milled to meet the hardwood floor in the horizontal plane, to meet the riser in the vertical plane. It is usually used on landings.

OSB Oriented Strand Board commonly used as an underlayment or subfloor material. Strands tend to be oriented with their length aligned with the panel length (typically). OSB is therefore stiffer and stronger when installed with the long axis across supports.

Overwood/Underwood A flooring condition in which there is a perceived misalignment of the flooring surface, with some wood pieces raised above adjacent pieces leaving a slightly uneven surface. Also called lippage.

Parquet A patterned floor.

Particleboard A generic term for a material manufactured from wood particles or other lignocellulosic material and a synthetic resin or other suitable binder. Flakeboard is a particle panel product composed of flakes. Oriented strand board is a type of particle panel product composed of strand-type flakes that are purposely aligned in directions that make a panel stronger, stiffer and with improved dimensional properties in the alignment directions than a panel of random flake orientation. Waferboard is a particle panel product made of wafer-type flakes. It is usually manufactured to possess equal properties in all directions parallel to the plane of the panel.

Photo-sensitive The property of some wood species which causes them to lighten or darken when exposed to light. See color change.

Pin-Worm Hole In hardwood flooring, a small round hole not more than 1/16-inch (1.5626MM) in diameter, made by a small wood-boring insect.

Pith The small, soft core occurring near the center of a tree trunk, branch, twig or log. First growth.

Plain Sawn The annual growth rings make an angle of less than 45° with the surface of the piece. This exposes the pores of the springwood and dense summerwood of the annual growth ring in ring-porous woods to produce a pronounced grain pattern.

Planer Bite A deeper than intended groove cut into the surface of a piece of wood by planer knives.

Plank Solid or Engineered/ boards 3" and wider designed to be installed in parallel rows.

Plywood Board or panel made of cross-directional veneers and/or layers of wood for dimensional stability.

Plugs Used to cover countersunk screws when installing wood flooring or for decorative purposes in wood flooring.

Prefinished Factory-finished flooring that only requires installation.

Quartersawn The annual growth rings of wood form an angle of 45° to 90° with the surface of the piece. In quartersawn strips, the medullary rays or pith rays in ring-porous woods are exposed as flecks that are reflective and produce a distinctive grain pattern.

Raised Grain A roughened or fuzzy condition of the face of the flooring in which the dense summerwood is raised above the softer springwood but not torn or separated.

Rays, Wood See Medullary Rays.

Reducer Strip A teardrop-shaped molding accessory for hardwood flooring, normally used at doorways, but sometimes at fireplaces and as a room divider. It is grooved on one edge and
tapered or feathered on the other edge.

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.

Rift Sawn Lumber (primarily hardwoods) in which the annual rings make angles of 30° to 60° with the surface of the piece. Also known as bastard sawn.

Ring-Porous Woods A group of hardwoods in which the pores are comparatively large at the beginning of each annual growth ring and decrease in size, more or less abruptly, toward the outer portion of the annual growth ring. The large pores are springwood and the smaller pores are summerwood.

Ring Shank Nail Headed nail for underlayment installation with rings on the shaft (shank) to improve the holding characteristics.

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.

Sapwood The wood near the outside of a tree. It is usually lighter in color than heartwood.

Sawn See Plain Sawn, Quartersawn and Rift Sawn.

Screed A wood member laid perpendicular to the finished floor, providing a nailing surface. Usually a 2-by-4 inch (50MM by 100MM) piece of wood laid flat side down and attached to a concrete subfloor to provide a nailing surface for tongue-and-groove strip flooring or a wood subfloor.

Shake A separation along the grain, the greater part of which occurs between the annual growth rings.

Sheathing The structural covering, usually sheets of plywood, placed over exterior studding, or rafters or subfloor of a structure.

Side-Matched In tongue-and-groove strip and plank flooring, the individual pieces have a tongue milled on one side and a groove milled on the opposite side, so that when the individual strips or planks are placed side by side, the tongue of one piece fits into the groove of the next piece. See End-Matched and Tongue-and Groove.

Slats See Fillets.

Sleeper Another name for screeds.

Slip-Tongue/Spline A small strip of wood or metal used to reverse or change direction in installing standard tongue-and-groove strip flooring.

Softwoods General term used to describe lumber produced from needle and/or cone-bearing trees (conifers).

Solid Board Group 1 A designation of a certain species based on density, strength and stiffness.

Split Separations of wood fiber running parallel to the grain.

Square Edge Flooring that abuts without a broken plane.

Squares Parquet flooring units, usually composed of an equal number of slats.

Streaks See Mineral Streaks.

Strip Flooring Solid or engineered boards, less than 3 inches in width, to be installed in parallel rows, produced in various thicknesses and widths. The strips are side-matched and end-matched (tongue-and-grooved). They are for nail-down installation directly to wood or plywood subfloors, or over wood screeds on concrete slab construction. Some types can also be glued directly to a concrete subfloor.

Surface The outside or exterior boundary of any substance. One is said to surface the work when it is rubbed or sanded to a smooth, level plane.

Tongue-and-Groove In strip, plank and parquet flooring, a tongue is milled on one edge and a groove cut on the opposite edge. As the flooring is installed, the tongue of each strip or unit is engaged with the groove of the adjacent strip or unit. See End-Matched and Side-Matched.

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

Trowel Fill Method to fill an entire floor or large area.

Truss Engineered or solid floor joist system.

Unfinished A product that must have stain and/or a finish applied after installation.

Vapor Impermeable Membrane A material or covering having a permeance rating of .15 perms or less when tested in accordance with the desiccant method, Procedure A of ASTM E-96. A vapor impermeable membrane limits the passage of moisture to near 0, or almost none.

Vapor Permeable Membrane A material or covering having a permeance rating of 5 perms or greater when tested in accordance with the desiccant method, Procedure A of ASTM E-96. A vapor permeable membrane permits the passage of moisture.

Vapor Retarder A vapor-resistant material, membrane or covering such as foil, plastic sheeting or covering having a permeance rating of 1 perm or less, when tested in accordance with the desiccant method, Procedure A of ASTM E-96. Vapor retarders limit the amount of moisture vapor that passes through a material, or floor, wall or ceiling assembly.

Warping Any distortion of a piece of flooring from its true plane that may occur in seasoning.

Working Pressure The pneumatic pressure range specified in pounds per square inch (PSI) to optimally run an air tool. (See tool manufacturer’s guidelines.) Note that these air pressures
should be metered at the tool

Copyright 2007 National Wood Flooring Association 8 Revised March 2007