January 12, 2024

Wood Flooring Terminology Guide

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Wood Flooring Terminology

If you’re using or planning to use reclaimed wood or any wood for your building project, you probably share the pride we have at Superior Hardwoods of Montana in making use of this amazing material. Reclaimed wood imbues your project with the rich history of the original life of that wood, whether it came from old barns, bridges, granaries or some other source. And with the exception of pallet material, it’s also great for the environment.
If you will be working with wood, however, there are some related terms you should know. The world of wood has its own language, and understanding these terms will enrich your knowledge and use of reclaimed wood. Here are some of the basic flooring vocabulary terms to know.

Glossary of Wood Flooring Terms


Abrasion Resistance

A surface’s ability to resist wearing away due to rubbing/friction. A function of toughness, rather than hardness.


Allowing the moisture content of the wood to reach equilibrium with the environment you are going to use it in. Also see Equilibrium Moisture Content.


Allowed to dry in the yard or woodshed without any artificial means, as opposed to kiln-dried.


Barn Beams/Timber

Pieces of wood that provide support for the structure of barns. For older barns from the 19th or early 20th century, these beams were often made from virgin timber.

Barn Wood

Wood that come from barns.

Base Shoe

Instead of a quarter-round in profile, this type of molding can be attached to a baseboard molding in order to cover expansion space.

Bastard Sawn

Usually hardwood lumber where the annual rings make 30 to 60 degree angles with the wood’s surface. See Rift Sawn.

Beveled Edge

An edge parallel to the face of a structure — the rounded or chamfered edge of wood flooring, parquet or a block or plank.

Board Foot

A unit of measurement standardized against a 1’ x 1’ that’s one inch thick. Usually based on nominal width and thickness and actual length. If lumber has a nominal thickness of less than one inch, it is calculated as one inch.


A customized design that frames your installed flooring.


A lumber defect. Warping of the wood along the length of the wood face.


A twist or swirl in the grain of the wood without a knot. Typically, burls appear in tree stops and places where the branches met the tree.


Chatter Marks

Small indentations spaced close together that cause a ripple effect on a wood floor surface.


As wood dries, cracks tend to emerge. Industry professionals call these cracks checks. Surface checks are fine unless you have an issue with the wood’s appearance, but deep checks can affect the structural integrity of the wood.


A barbed device used to fasten hardwood flooring.

Color Change

Chemical reactions, light exposure/deprivation and air deprivation can all cause observable changes in the color of the wood.


Lumber that comes from cone- or needle-bearing trees, or conifers. See Softwoods.


In contrast to a bow, a warping perpendicular to the edge of the board.

Cross Directed

Material laid in a perpendicular orientation above another piece of material.

Crowning and Cupping

Crowning and cupping are simply lumber terminology for concave and convex bowing of a board. A concave board, with raised edges relative to the center, is cupping, while the reverse, a convex board with a raised center, is crowning.



Wood from broad-leaved trees like Oak or Ash, as opposed to coniferous trees like Pine.


A defect where the layers of an engineered wood floor come apart due to adhesive failure.


A technique designed to give a wood floor a vintage appearance by creating a scraped or scratched texture.


How resistant a wood species is to destructive agents or conditions that it may come into contact with when put to use.


Eased Edge

See Beveled Edge.

End Joint

The location where two ends of pieces of flooring are joined together.

End Lifting

A swelling at an end joint of engineered wood flooring.


Milling individual planks with a tongue on one end and a groove on the other in a tongue-and-groove strip system so the planks fit together end-to-end.


The process of making flooring by bonding layers of lumber or veneer with adhesive together with grains perpendicular to each other for greater dimensional stability.



Over time, exposure to light, heat and other elements can cause color loss in the wood.


Name given to a variety of methods of attaching wood flooring to a subfloor. Can be chemical or mechanical.

Feature Strip

An accent strip of wood used to highlight a threshold or border of a room, typically a different color than the wood it borders.


Any natural markings on the surface of the wood that the annual growth rings produce, like knots, rays or other grain irregularities.


Any substance used to fill holes in planes or sanded surfaces to create uniformity and decrease porosity before applying the finish coating. Usually a putty of some kind, possibly mixed with sanding dust.

Fire Retardant

A chemical substance used to stop the spread of a fire or to reduce flammability.


A specific, banner-shaped, dark, heavy mineral streak.

Flag Worm Hole

Worm hole within the flag.


A wide, irregular figure that appears in quarter sawn oak flooring.

Floating Floor

A floor where the panels are connected mechanically or through adhesive, that does not need to be attached to the subfloor by nailing or gluing.


How well a coating spreads into a uniformly thick film before it hardens.


Grain Pattern

Vertical and flat grain, as mentioned above, are types of grain patterns. Other types are plainsawn, which is a cathedral grain pattern, and curly, which is a much rarer pattern.

Growth Rings

Yearly growth rings in trees are made up of a light-colored spring band and a darker late season band. These rings give the wood its grain pattern.


Hand Hewn

Hand hewn wood is wood cut into lumber using a special adze tool, rather than a circular saw or band saw. Hand hewing creates a unique, natural look due to the distinctive cuts in the wood caused by the adze that you don’t get from the uniform action of a saw.


Hardness is naturally a desirable quality in wood. The name of the scale that measures hardness is the Janka Scale.

Heart Content

Heart content is how much heartwood your lumber contains vs. sapwood. See Sapwood/Heartwood below.

Heavy Streaks

Streaks or spots so large and dense that they ruin the look of the wood.


Checks that appear in the interior of the wood, typically parallel to the wood rays.


A measure of the concentration of water vapor in the air.


An instrument designed to measure humidity in the atmosphere.


Insect Bore Holes and Tracks

While this may sound alarming, it’s actually a reference to damage that may have been done to the wood long ago, creating minor holes and tracks that are no longer a threat to the wood but create a distinctive, rustic look.


Janka Hardness Test

The test used to measure a wood species’ Janka score. Standardized by the amount of lb./sq. in. it takes to embed a .444-inch steel ball halfway into a piece of wood. See Janka Scale.

Janka Scale

A measure of wood hardness, or how well a wood species can resist denting, scratches and wear. Black Walnut, for example, has a Janka rating of 1,000 lbs./sq. in., so it is only about a third as hard as Brazilian Rosewood, with a Janka score of 3,000.


A beam that, along with other parallel beams, supports ceiling or floor loads. The joists themselves are supported by load-bearing walls, larger beams or girders.


Kerf Marks

These are the curving saw blade marks across the grain of the wood that whoever initially milled the wood made.


An oven used for drying lumber, veneer or other wood products.

Kiln Drying

This is a procedure that involves using heat and dehumidifying to remove moisture from the wood in order to minimize shrinkage and make the lumber more workable for a building’s interior.


Knots are dark formations in the wood where a limb was once attached. Fewer knots indicate a higher grain of wood.


Live Sawn

Each plank is cut straight off of the log in one direction without changing the orientation of the log. This method produces a mix of plain grain, rift sawn as well as quarter sawn.


Manufacturing Defects

Any defects in the wood that come out of the manufacturing process, like torn or chipped grain, skips, mismatching and machine burn.

Mechanical Fastener

A device used to attach layers of wood flooring during installing that is mechanical, like a nail, cleat or staple. Mechanical fasters are usually coated or serrated for greater holding power. The fastener is usually best applied at the horizontal part of the tongue where it becomes the vertical edge of the wear layer. Fasteners may be applied on the face or, in some situations, the groove side.

Medullary Rays

These are strips of cells of a tree that store food and transport it horizontally by extending radially through the tree. They can be barely noticeable or as much as four inches high in Oak. They are the source of flecks in quarter sawn oak.

Mineral Spirits

Solvent used for cleaning or thinning.

Mineral Streak

A streak of unnatural greenish brown or black color in the wood caused by sap flow.

Moisture Content

The percentage of the weight of oven-dried wood attributable to moisture.


Nailing Shoe/Nailing Plate

Part of a blind nailing machine used to increase the impact area, usually used when attaching factory-finished flooring.

Nail Staining

This happens when the metal of a nail bleeds into the wood around the nail hole.

Nominal Size

The size designation by which a piece of lumber is sold, possibly distinct from actual size.


A special hardwood molding often used on landings that covers the outside corner of a step and is milled to meet the riser in the vertical plane and the hardwood floor in the horizontal plane.


Old Growth

Old growth timbers are over 120 years old and because of the dense canopy during that time period the growth rate was slower and created more densely compacted growth rings that make the wood harder and able to last much longer than new lumber from faster growing trees.

Overwood/Underwood (Lippage)

A misalignment of the flooring surface where certain wood pieces are slightly above or below adjacent pieces creating an uneven surface.



A floor material made from wood particles that are glued together to make a stronger surface. Some versions include waferboard, where the panels are made up of wafer-type flakes, or oriented strand board, where the flakes are specially aligned to make the panels stronger and stiffer.


Sensitive to light. Some wood species that are more photosensitive may be quick to get lighter or darker under light exposure.

Pin-Worm Hole

A small (1/16” or smaller in diameter) round hole in hardwood flooring made by a wood-boring insect.

Pitch Pockets

Pitch pockets are small collections of crystallized resin that are sometimes, but not often, found in the wood.


The soft core near the center of a log, branch or tree trunk.

Plain Sawn

Cut where the annual growth rings make an angle of less than 45° with the surface of the piece. In ring-porous woods, this cut produces a unique grain pattern.

Planer Bite

Cutting a groove into the surface of the wood with planer knives deeper than intended.


A piece of wood that is an engineered board at least three inches wide, installed in parallel rows.


Decorative covers for countersunk screws to hide the head of the screw in wood flooring.


Panels or boards that consist of cross-directional layers of wood or veneers to increase dimensional stability.


Flooring that is already fully finished in the factory and only needs to be installed.


Quarter Sawn

Cut where the wood is such that the annual growth rings make an angle of 60 to 90 degrees with the surface of the wood. In this cut, the medullary rays produce flecks, a distinctive, reflective grain pattern. Contrasted with plain sawn or rift sawn (bastard sawn) wood.


Raised Grain

Flooring with a rough appearance where the summerwood is raised above the less dense springwood but still connected.

Random Width

With typical flooring, all planks are the same size and width to give the floor a uniform look. For a more rustic, unique appearance for your floor, you may wish to choose boards that are not all the same width called a random width or mixed-width floor.


Also referred to as Wood Rays. See Medullary Rays


Reclaimed wood from old growth timber is not merely recycled wood. It is a process of taking a piece of wood originally used for one purpose and then milling it to create a piece you can use for a higher-quality purpose.

Reclaimed Flooring

Hardwood flooring made from reclaimed wood. A way to beautify your home with a natural-looking floor while still being responsible to the environment. See reclaimed, above.

Reducer Strip

A molding used for hardwood flooring at doorways, or sometimes at fireplaces or to divide a room. It has a teardrop shape, grooved on one edge and tapered at the other.

Relative Humidity

A measurement that is the ratio of current humidity to the maximum humidity at that temperature, most accurately based on vapor pressures.

Rift Sawn

Lumber cut so that the annual ring growth makes an angle between 30 and 60 degrees with the surface of the wood. Also called bastard sawn.

Rough Sawn

Current lumber that is not hand hewn is smooth sawn, meaning it is cut with a band saw. Prior to 1930, lumber was cut with a circular saw, which was an improvement over using an axe with respect to efficiency, but it wasted a lot of wood and left a rough finish. Now that rough sawn wood is rarer, many find that rough finish desirable.



Salvaged wood is wood that comes from trees that fell naturally, as from a storm, rather than from a tree that someone cut down specifically to use as lumber.


If you look at the open face of a log, the outer layer of wood is the sapwood, while the wood closer to the center is the heartwood. Sapwood tends to be softer and more rot-prone than heartwood, but lumber cut too close to the actual heart, or center of the log, is more likely to split.


How the wood is cut. See Plain Sawn, Quarter Sawn, Bastard Sawn or Rift Sawn.


These are cracks you may find in between growth rings with natural lumber. They will often be vertical cracks at the end of a board. You will generally want to cut off the shakes before you use this lumber.


A tongue-and groove system where the groove and tongue are on opposite sides of the plank, rather than on the ends, so the planks fit together side by side. See Tongue and Groove and End-Matched.


Small pieces that comprise finger-block parquet. Also called fillets or fingers.


A 2” x 4” piece of wood attached to a concrete subfloor to create a nailing surface for a wood subfloor or tongue and groove flooring. Also called a screed.


When installing tongue-and groove strip flooring, the spline is a strip of wood or possibly metal for reversing direction.

Smooth Sawn

The appearance of lumber cut with a band saw, as is the practice for most modern lumber. See Rough Sawn, above.


See Coniferous.


Places where the wood fiber running parallel to the grain separates.

Square Edge

Flooring that abuts with no broken plane.


A distinct unit of a parquet floor. Each square usually has the same number of slats.


See Mineral Streak.

Strip Flooring

A type of flooring consisting of tongue and grooved boards installed in parallel rows. They may be up to three inches wide of various thicknesses. They can be installed by nailing them to wood or plywood subfloors or on a concrete subfloor, either glued directly or over a wood sleeper.


The exterior boundary of a piece of wood. Surfacing the wood refers to rubbing it or sanding it smooth.

Surface-4-Sides (S4S)

If flooring is not on a tongue-and-groove system, it is on a surface-4-sides system. Face-nailed square-edge strip flooring may also be referred to as S4S flooring.


Textured Flooring

Giving the face of the flooring a rough or raised texture.  There are many ways to change the texture of the flooring.  Circular Sawn marks, wire-brushing, hand scraping or hand planning are a methods of changing the flooring texture.


A way of connecting plank, parquet or strip flooring where a tongue on one edge fits into the groove on the edge of the adjacent plank. Can be end-matched or side-matched depending on where the groove and opposing tongue are located on the piece of wood.


A renewable resource that must be protected that is the source of all wood products.


Finish materials for a floor like base shoe, baseboard or quarter round.

Trowel Fill

A specific procedure for filling a large area, like a complete floor.



A wood product after installation but before the finish has been applied.


Vapor Retarder

A covering material with a permeance rating of 1 perm or lower, used to reduce the amount of moisture vapor passing through a floor or other material.
Vertical Grain or Straight Grain

Wood where the growth rings create a vertical pattern — see Flat Grain, Grain Pattern and Growth Rings.



Distortion of a piece of flooring from its natural plane.

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