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It's not uncommon for homeowners to become overwhelmed by hardwood flooring's specific terminology used in the flooring business during the process of searching for a new wood floor. Here, we offer a brief description of some terms used most often when discussing hardwood flooring. Many of these are linked to more in-depth articles regarding that specific hardwood flooring term.

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Above Grade

any level of the home located above the soil line.


the period of time prior to installation that a hardwood floor needs to adjust to the moisture content and temperature of the environment in which it's to be installed and maintained.

Acrylic Infused/Impregnated

an engineered floor in which the acrylic stain/finish isn't just coated along the top of the board, but rather injected into the wear layer of the flooring, filling the pores and creating a more durable surface.

Aluminum Oxide

the most common finish type for prefinished hardwood flooring. Includes minuscule particles of aluminum in one or more of the coats of finish, which create a more durable and scratch resistant surface than standard polyurethane finishes.



Balancing Layer

the bottom wood ply layer of an multi-ply engineered floor plank that matches the same wood species used on the top decorative wear layer of the plank, adding stability during seasonal relative humidity level changes.

Below Grade

a level of the home located below the soil line (basements).


the slightly sloped edges and ends of a hardwood flooring plank. Variations in size include full bevel, micro-bevel, eased edge or micron-bevel (the smallest).


a rare pattern appearing in select wood species (mostly in maple) which has distinctive cream colored spots, named because they look similar to swirling birds eyes.

Black Felt Paper

necessary for a nail or staple down installation, helps to reduce any moisture transfer up through the subfloor and into the bottom of the wood flooring.

Chair Glides

felt circles, which when attached to chairs and other pieces of furniture, prevent scratching and denting of hardwood flooring.

Click Lock

created for easy floating installation (especially for Do-It-Yourself installations). The edges and ends of the hardwood flooring planks have special curved tongue and grooves which, when fitted together, lock and create a strong hold and a tight seam without the use of glue.

Color Variation

hardwood flooring is created from a product of nature where each board can have color variations. Sometimes a particular wood species will have slight to moderate to heavy color variation from board to board within the flooring carton. The level of color variation is dependent upon the type of wood species and the grade of the flooring. A higher flooring grade will generally have more uniform color from board to board. All wood flooring will have, to some extent, varying coloration.

Commercial Finish Warranty

usually specifies either light or heavy commercial use. This is the number of years the particular manufacturer will offer their finish warranty for with use in a commercial setting. Finish warranties do not cover denting, scratching, water damage or improper installation.

Concrete Slab

a type of subfloor you can install engineered flooring over.


the way the hardwood flooring plank is assembled --- can be solid, engineered or solid sawn (structured).


when the homes atmosphere is dry, moisture can evaporate from the cells of the hardwood flooring and causing the boards to contract in size. Engineered boards are less affected than solid boards. Slight seasonal gapping between boards may occur --- this slight gapping is to be expected and is considered normal across the industry. To minimize this contraction the Homes relative humidity level should be maintained between 30 -60 %.


In engineered flooring, cross-ply is where the ply layers under the actual decorative wear layer are assembled in alternate directions, leading to exceptional plank stability. These ply layers are typically made of softer birch, pine or even hardwood.


damage to a hardwood floor resulting in the edges of the planks curling down. Usually due to the presence of excessive moisture in the environment from above the floor. Or a cupped water damaged floor that was sanded and refinished before the flooring was allowed to dry out.


damage to a hardwood floor resulting in the edges of the planks curling up and forming a U shape. Usually due to the presence of excessive moisture coming from below the floor.


when a color or style of hardwood flooring is no longer available from a particular manufacturer. Product lines are constantly changing. Discontinued products are sometimes difficult, if not impossible, to find.


type of texture of a hardwood floor board where the surface has been "antiqued" by using a variety of methods including, but not restricted to: dents, burn marks or blackening of edges.

Domestic Wood Species

wood species which are prevalent in North America (e.g. red oak, white oak, maple, hickory).


a type of construction of hardwood flooring where thinner ply layers of wood are cross layered together to make a wood floor board.

Exotic Wood Species

wood species which are prevalent in Central and South America (e.g. brazilian cherry, santos mahogany, kempas, brazilian teak).


when the atmosphere contains more moisture in the air, the minuscule water molecules will fill the pores of the hardwood boards causing the planks to expand slightly. When flooring boards are installed, there should be expansion gaps left at all fixed objects like columns and walls.

Expansion Gap

the space left between the hardwood flooring and fixed objects in the room during installation (walls, cabinets, kitchen islands, etc.). The expansion gap makes sure there is enough room for slight movement during expansion and contraction. This gap can be covered after installation is complete with a quarter round or wall base.

Expansion Joint

with floating hardwood flooring, there is a limit to how far you can span the floor boards across a large room before you need to create an expansion gap --- which is then covered with a matching T-Molding. The maximum span of floating hardwood flooring differs from manufacturer to manufacturer. It can range from 20' to 40' or greater. Check with your specific manufacturer for their requirements.

Face Nail

during installation, nailing directly into the face of a plank to secure it to the subfloor. The first two or three boards and the last two rows of boards against a wall (in a nail down or staple down installation) are typically face nailed because the nail/staple gun cannot be placed that close to the walls. Holes created with by face nailing can be filled with either putty (for a prefinished hardwood floor) or wood filler (for an unfinished hardwood floor).


a putty like material used to fill holes or irregularities in hardwood flooring planks.


the coating used on the surface of a hardwood flooring plank to protect the raw wood underneath.

Floating Installation

when a hardwood floor is not attached to the subfloor; but, rather, planks are attached to each other and as a whole are held down by gravity and the weight of the flooring. Floating floors are typically engineered constructions and require the use of an underlayment pad.

Flush Reducer

for use with a nail, staple or glue down hardwood floor, the flush reducer connects to the hardwood and gradually slopes down to transition to vinyl, the edge of tile or low pile carpet.

Flush Stairnose

for use with a nail, staple or glue down hardwood floor, the flush stairnose connects to the hardwood and acts as the finished part of a step when using the hardwood flooring to build the stair.

Forest Stewardship Council (FSC)

an international organization promoting responsible management and use of the world's forests. Hardwood flooring manufacturers can pay yearly dues to become affiliated with the FSC.

French Bleed

edges and ends of hardwood floor planks are darkened, usually with a chemical, for a specialized antique appearance.

Glue Down

securing engineered or thinner solid hardwood planks directly to the subfloor using a wood flooring adhesive.

Grade Level

refers to the level of the home where the flooring is going to be installed: on grade, above grade or below grade.

Grain Pattern

different wood species have different visual appearances. The grain pattern refers to the cells of the particular tree which, when cut into boards, appear in specific patterns depending on the wood species.


a simulated antiqued look for hardwood flooring created with scrapers and other indentation tools. Handscraping is sometimes done by hand, most of the time, though, manufacturers incorporate the use of handscraping machines.

Hardness Rating (Janka)

the Janka hardness rating of a wood species measures the force needed for a steel ball to imbed half its diameter into that particular wood species. The harder the wood species, the better it is at standing up to residential or commercial traffic.

High Density Fiberboard (HDF)

strong and more durable than regular particleboard, HDF is featured in the construction of many laminate floors as well as some engineered flooring. HDF is created with compressed wood fibers.

Knot Hole

the section of a tree where the trunk intersected with one of the tree's branches. Knot holes are predominately featured in Rustic Grade hardwood flooring, but may appear sparingly in other grades.

Lifetime Structural Warranty

the guarantee a manufacturer makes on the structural integrity of their hardwood flooring. Usually this guarantees against the ply layers separating. This structural warranty is typically void if there is a presence of excessive moisture coming up from the subfloor.


a type of click locking engineered flooring which features either 1-strip, 2-strips or 3-strips per plank.


tiny water molecules which, in excess, can damage hardwood flooring beyond repair. Most manufacturers require a specific moisture content range in which your subfloor and hardwood flooring must fall for installation of their hardwood flooring.


finishing pieces for your hardwood floor. Most brands offer moldings and transition pieces to match the flooring they make, while some homeowners prefer to stain or pain their own pieces to match the rest of the trim in their homes.

Nail Down

one of the most common installation methods for solid hardwood and engineered flooring. Requires a plywood subfloor.

National Wood Flooring Association

a national organization in which its members strive to maintain professionalism and follow-up training in all things related to hardwood flooring.

Oil Finish

a finish used instead of the standard urethane or aluminum oxide finish. Requires a bit more maintenance than standard prefinished hardwood flooring but provides a more hand rubbed appearance and easier reparability.

On Grade

the ground floor of the home. Most hardwood flooring is approved for installation on grade.


a type of subfloor made of glued together wood chips.

Overlap Reducer Strip

a transition piece to be used in conjunction with a floating floor. The overlap reducer will overlap the hardwood flooring and gradually slope down to meet vinyl, tile or carpet. The part that overlaps the hardwood covers up the necessary expansion gap. The overlap reducer should be attached to the subfloor and never to the actual hardwood flooring.

Overlap Stairnose

for use with a floating hardwood floor, the overlap stairnose acts as the finished rounded part of a step. The overlap stairnose will overlap the hardwood floor, covering the necessary expansion gap. The overlap stairnose should be attached to the subfloor and never to the actual hardwood flooring.


tiles of hardwood flooring featuring wood blocks arranged into a geometric and/or angular pattern.

Particle Board

a type of subfloor typically found under old carpet consisting of tiny wood particles that are glued together and pressed into 4' x 8' sheets. Particle board is not a suitable subfloor type for hardwood flooring and it's always recommended to remove it prior to installation. Engineered flooring and laminate flooring can be floated over particle board if absolutely necessary.


the degree of color change a wood species will experience when exposed to light.

Plain Sawn

milling of a tree trunk involving parallel cuts all the way through. Plain sawn flooring offers the traditional grain patterns with an oak wood species and is the simplest form of milling, creating the least amount of waste.


a hardwood board which is 3 IN. or wider.


the number of layers of a cross-ply engineered hardwood floor.


a common type of subfloor made of multiple layers of wood.


when a hardwood floor is finished at the factory rather than on-site. There are many benefits to using a prefinished hardwood floor instead of a site-finished floor.

Quarter Round

sometimes used in conjunction with a wall base, sometimes used alone. A quarter round is used to cover up the necessary expansion gap around the wall of the room. Attached to the wall, not to the hardwood flooring.


the milling of a tree trunk involving cuts on a diagonal from the core of the tree. This type of milling basically follows the grains of the tree straight on and creates a beautiful and more stable plank with long, linear lines and grain flecks. Quartersawn milling does produce a lot more waste during the manufacturing process . Quartersawn planks can be installed over radiant heating systems.

Radiant Floor Heating System

a heating system located within the subfloor which heats a room from the surface of the floor up.

Random Lengths

many hardwood flooring manufacturers will package their flooring in cartons with random lengths. Range varies from product to product but are usually 12" to 96" lengths.

Random Widths

for a more country or casual appearance, a brand may package a variety of widths of the same wood floor into one carton.

Reclaimed Wood

often taken from old mills, barns or farmhouses that are being dismantled, reclaimed wood is re-milled and refinished into new flooring planks and offer an old, used, lived-in appearance.


taking the current finish off of a hardwood floor, sanding and re-applying a new finish for an updated look.


a gloss used to recoat the original shine of a hardwood floor after years of use have dulled it.

Residential Finish Warranty

the number of years the finish on a prefinished hardwood floor can be used in a normal residential setting without the finish wearing off the floor. Does not cover dents, scratches, stains, water damage or small sections of finish loss.


the wood board part of a staircase positioned vertically behind the stair tread.


the gloss level of the finish on a hardwood floor. Varies from brand to brand. Popular options include high gloss, semi-gloss and satin.


when an unfinished hardwood floor is installed, sanded and finished on location.


usually 3/4 IN. in thickness (although it can be thinner), solid wood is just that --- a solid piece of wood milled into a flooring board.

Square Edge

the edge of wood floor boards that have no beveled edges when the boards are put together. Square edges and ends are hard to find in prefinished wood flooring, as the standard in the industry right now is a bevel variation.

Square Nose Reducer

a transition piece that overlaps the wood flooring and comes to a finished square edge at carpet or vertical objects (like a fireplace hearth).

Staple Down

one of the most common installation methods for solid hardwood and engineered flooring. Requires a plywood subfloor.


a hardwood board which is 2-1/2 IN. or narrower.


the level on which the new hardwood flooring will be attached or floated over.


a wood piece shaped like a T to smoothly transition from one hard surface to another that is of equal height.

Threshold (Baby Threshold)

a transition piece which overlaps the hardwood flooring and then reduces down to the floor to give the flooring a finished edge. Used against sliding glass doors, tile, high pile carpet, etc. The overlap portion covers the necessary expansion gap. The threshold should always be attached to the subfloor and never to the hardwood flooring.

Titanium Finish

an exclusive hardwood flooring finish created with no solvents or VOCs. Titanium finishes offer an extremely clear and durable coating, allowing the full beauty of the wood species to shine through.

Tongue and Groove

often referred to as male or female ends, the tongue and grooves are found at the edges and ends of hardwood flooring boards and fit snuggly into one another to connect the boards.


the horizontal part of a stair, which you step on. Prefinished hardwood flooring stair treads are available and are easier to install than piecing a stair together with pieces of flooring. Most hardwood flooring brands do not offer their own stair treads to match their products, but there are independent stair part companies which will match the tread to your flooring.


a hard or soft barrier between the subfloor and the new hardwood flooring.


hardwood flooring planks which are milled, but not finished at the factory. Used when site finishing is desired.

UV Cured

the drying stage of the production of prefinished hardwood flooring where the boards are placed under ultraviolet lights to harden the finish. This creates a much more durable finish than what you can get with site finished flooring.

Vapor Barrier (Moisture Barrier)

a plastic sheet, usually 4 to 6 mil thick, layed directly over a concrete slab to retard any moisture coming up through the subfloor. Many underlayments already have a vapor barrier attached, so you don't need to use a separate one. Vapor barriers are absolutely necessary for floating installation over concrete and below grade.

VOCs (Volatile Organic Compounds)

carbon based chemicals, which when inhaled in large quantities may increase the risk of health problems. Some people are more sensitive to VOCs than others. "Off gas" VOCs can come from a number of household sources, including carpet, furniture, paint, plastics, electronics and more.

Wall Base (baseboard)

molding that is used to cover up the necessary expansion gap around the edge of a room. Attached to the wall, not the flooring.

Waste Factor

the amount of extra wood that should be ordered to make up for square footage lost to cutting, fitting or discarding of boards that do not fit the grade ordered. Typically, a 5% waste factor is recommend. Increase that to 10% for rooms with unusual angles or if you want to be more choosey with which boards you install.

Wear Layer

the top layer of an engineered hardwood floor. Typically, the thicker the wear layer the better and the more value the flooring has. The wear layer dictates how many times an engineered floor can be sanded and refinished.


the process of creating texture on the surface of a hardwood floor which usually accentuates the grain patterns of a wood species.

Wood Grade

the grade category that a hardwood floor is culled out from a batch of wood boards during the manufacturing process to determine the clarity, color variation and character marks.

Wood Species

the specific tree that the hardwood flooring is made of. Different wood species feature different coloring, grain patterns and hardness.

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