Reference

Flooring Glossary

The words that come up in estimates, product sheets, and installation instructions — defined properly, so you can read a quote and know exactly what you're agreeing to.

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47 Terms

Flooring, Defined

Every definition here describes the term as the trade actually uses it. Where a figure is set by the manufacturer's installation instructions rather than by a universal standard, we say so instead of inventing a number.

Category

Materials & Construction

Click-Lock: A mechanical edge profile that locks boards to each other without glue or fasteners, usually by angling one plank into the next and dropping it flat, or by tapping it home. Click-lock is what makes most floating installations possible, and the joint's strength is a property of the milling — damaged or dirty edges will not lock fully and show up later as gaps.; See also: Floating Floor, Tongue and Groove, Subfloor Flatness
Engineered Hardwood: A floorboard built as a sandwich: a real hardwood wear layer bonded to a core of plywood or high-density fiberboard. Plywood cores are laid up with their plies running in alternating directions, and that cross-grain construction — like the dense, uniform HDF alternative — resists the seasonal expansion and contraction that moves solid wood. It is why engineered products are the usual choice over concrete slabs and over radiant heating.; See also: Solid Hardwood, Wear Layer, Radiant Heat Compatibility
Mil (Wear Layer Thickness): A unit equal to one thousandth of an inch, used to state the thickness of the clear wear layer on vinyl flooring. A higher mil figure means more material above the decorative film and, all else being equal, more resistance to scratching and wear-through. Mils are not millimeters — engineered wood wear layers are quoted in millimeters or fractions of an inch instead.; See also: Wear Layer, SPC (Stone Plastic Composite), WPC (Wood Plastic Composite)
Solid Hardwood: A floorboard milled from a single piece of wood through its full thickness, with no layered core. Because the entire board is wood, it responds to moisture across its whole section, and it can be sanded and refinished repeatedly over its life — limited only by the thickness of material above the tongue. It is normally fastened to a wood subfloor rather than installed over concrete.; See also: Engineered Hardwood, Nail-Down, Moisture Content
SPC (Stone Plastic Composite): A rigid-core vinyl plank whose core blends limestone powder with PVC. The mineral filler makes the core dense, stiff, and dimensionally stable, so SPC planks resist indentation and telegraph less movement from the subfloor beneath them. The trade-off is a harder, colder, louder floor underfoot, which is why SPC is often paired with an attached or separate acoustic pad.; See also: WPC (Wood Plastic Composite), Underlayment, Click-Lock
Tongue and Groove: An edge profile in which a projecting tongue milled along one edge and end of a board fits into a matching groove on the next. The joint aligns adjacent boards vertically, spreads load across the seam, and gives cleats or staples something to bite into when they are driven at an angle through the tongue and hidden by the following row.; See also: Click-Lock, Nail-Down, Staple-Down
Underlayment: A layer installed between the structural subfloor and the finished floor. Depending on the product it can smooth minor subfloor irregularities, cushion footfall, reduce sound transmission between stories, or carry a moisture retarder. Underlayment is not a substitute for a flat, sound subfloor, and floating floors and nail-down floors call for different underlayment types.; See also: Subfloor, Vapor Barrier / Vapor Retarder, Floating Floor
Wear Layer: The top portion of a floor that takes traffic and can be renewed. On engineered wood it is the real hardwood veneer above the core, and its thickness determines how many times the floor can be sanded. On vinyl and laminate it is a clear protective coating over the printed or embossed decorative layer, and it cannot be sanded at all.; See also: Mil (Wear Layer Thickness), Sand and Finish, Engineered Hardwood
WPC (Wood Plastic Composite): A rigid-core vinyl plank whose core combines PVC with wood flour and a foaming agent. The foamed core makes WPC thicker, lighter, and softer underfoot than SPC, with a warmer feel and better sound absorption. Because that core is less dense, it is generally more prone to denting under heavy point loads such as appliance feet or narrow furniture legs.; See also: SPC (Stone Plastic Composite), Mil (Wear Layer Thickness)

Category

Milling & Grain

Janka Hardness: A standardized test of a wood's resistance to denting, performed by pressing a steel ball into a sample until it is embedded to half its diameter and recording the force required. Results are reported in pounds-force in the United States, and higher numbers indicate greater resistance to denting. Species are commonly compared against red oak, the trade's usual reference point.; See also: Solid Hardwood, Wear Layer
Plain Sawn: The most common and highest-yield way to cut a log, producing boards whose growth rings run roughly parallel to the face. The result is the familiar cathedral or flame figure. Because the rings lie flat relative to the board's face, plain sawn stock moves more across its width with changes in humidity than quarter sawn or rift sawn boards of the same species.; See also: Quarter Sawn, Rift Sawn, Moisture Content
Quarter Sawn: A cut that produces boards whose growth rings meet the face close to perpendicular, giving a straight, linear grain and — in oak — the prominent ray fleck that quarter sawn stock is prized for. Quarter sawn boards move less across their width than plain sawn, at the cost of lower yield from each log and a correspondingly higher price.; See also: Plain Sawn, Rift Sawn
Rift Sawn: A cut taken at an intermediate angle between plain sawn and quarter sawn, yielding boards with a consistently straight, tight grain and none of the ray fleck that quarter sawn oak shows. Rift sawing is the most wasteful of the three cuts and therefore the most expensive, and it is specified when uniform linear grain across an entire floor matters.; See also: Quarter Sawn, Plain Sawn

Category

Moisture & Subfloor

Acclimation: Storing flooring at the jobsite until its moisture content stabilizes near the level it will hold in service. Acclimation is not a fixed waiting period — a floor is acclimated when meter readings stop moving, in a space held at normal living temperature and humidity. Delivering material into an unconditioned house, or one still drying out from plaster or paint, defeats the purpose.; See also: Moisture Content, Cupping, Expansion Gap
Expansion Gap: The deliberate space left between a wood or floating floor and every fixed vertical surface — walls, columns, door jambs, thresholds — so the floor can expand seasonally without pressing against something rigid. The gap is concealed by baseboard or shoe molding, never filled with caulk or pinned down by trim fastened through the floor. Omitting it is a common cause of buckling.; See also: Buckling, Floating Floor, Transition Strip
Moisture Content: The amount of water in wood, expressed as a percentage of the wood's oven-dry weight. Wood continuously gains and loses moisture until it reaches equilibrium with the surrounding air, and it changes dimension as it does. Both the flooring and the subfloor are metered before installation begins, because a large difference between the two predicts gapping or cupping once the floor is down.; See also: Acclimation, Cupping, Subfloor
Moisture Mitigation: Treating a concrete slab that is emitting more moisture than the flooring or its adhesive can tolerate, usually with a roll- or trowel-applied membrane that reduces vapor transmission before the floor goes down. It follows testing rather than guesswork: the two standard methods are an in-situ relative humidity probe set into the slab and an anhydrous calcium chloride test placed on it.; See also: Vapor Barrier / Vapor Retarder, Subfloor, Glue-Down
Subfloor: The structural sheet material — typically plywood or OSB over joists, or a concrete slab — that the finished floor is installed on or over. It carries the load and it defines which installation methods are possible: a wood subfloor accepts fasteners, while a slab generally rules out nailing and pushes the choice toward glue-down or floating systems.; See also: Subfloor Flatness, Underlayment, Moisture Mitigation
Subfloor Flatness: How close a subfloor comes to a true plane, measured as the maximum deviation under a straightedge across a stated span — not to be confused with level, which is about slope. The allowable tolerance comes from the flooring manufacturer's installation instructions and is tighter for glue-down and click-lock floors than for nail-down. High spots are ground off; low spots are filled with patching compound.; See also: Subfloor, Glue-Down, Click-Lock
Vapor Barrier / Vapor Retarder: A sheet material that slows water vapor moving from below — out of a crawlspace or up through a concrete slab — into the flooring assembly. “Retarder” is the more accurate word, since these products reduce vapor transmission rather than stop it outright. Whether one is required, and how permeable it may be, depends on the subfloor and on the flooring manufacturer's instructions.; See also: Moisture Mitigation, Underlayment, Subfloor

Category

Installation Methods

Floating Floor: An installation in which the flooring is not fastened or glued to the subfloor at all — planks connect to one another and rest on the subfloor, held in place by their own weight and the perimeter trim. Floating installations tolerate a wider range of subfloors and go down quickly, but the whole field has to stay free to move, so expansion gaps and unobstructed transitions matter more.; See also: Click-Lock, Expansion Gap, Underlayment
Glue-Down: Bonding flooring directly to the subfloor with a troweled adhesive. It is the standard approach for engineered wood over concrete and for many vinyl and tile products, and it produces a floor that feels solid underfoot with no hollow sound. Glue-down is unforgiving of an out-of-flat or contaminated subfloor, because adhesive will not bridge a void.; See also: Subfloor Flatness, Moisture Mitigation, Floating Floor
Nail-Down: Fastening solid or engineered boards to a wood subfloor with cleats driven at an angle through the tongue, so each fastener is hidden by the next row. Cleats have a barbed or serrated shank that grips the subfloor while still allowing the board a little seasonal movement. Nail-down requires a wood subfloor — it is not an option directly over concrete.; See also: Staple-Down, Tongue and Groove, Solid Hardwood
Staple-Down: A nail-down variant using crown staples in place of cleats. Staples hold a board more tightly to the subfloor than cleats do, which can be an advantage for stability and a disadvantage for solid wood, since a board held rigidly has fewer ways to relieve seasonal movement. Which fastener to use is normally specified by the flooring manufacturer.; See also: Nail-Down, Tongue and Groove

Category

Finishes & Refinishing

Dustless Sanding: Sanding with equipment connected to a sealed vacuum containment system that captures most airborne dust at the source. The term is a trade convention rather than a literal claim — no system captures every particle, and containment and cleanup still matter. The practical benefit is dramatically less fine dust settling through the rest of the house during a refinish.; See also: Sand and Finish, Site-Finished
Hand-Scraped: A texture that mimics the undulating surface of a floor leveled by hand with a scraper. Genuinely hand-worked floors vary from board to board; most factory versions are machine-applied to a repeating pattern, which becomes noticeable across a large area. The texture is heavier and more rustic than wire-brushing, and similarly forgiving of everyday wear.; See also: Wire-Brushed, Prefinished
Prefinished: Wood flooring that arrives already sanded, stained, and coated from the factory, typically with a more abrasion-resistant coating than can be applied on site and a micro-bevel milled along the edges. Installation is faster and the floor is usable almost immediately, but each board reads as a distinct piece and the beveled seams stay visible for the life of the floor.; See also: Site-Finished, Wear Layer
Sand and Finish: A full refinish: abrading the floor back to bare wood through a sequence of progressively finer grits, then applying stain if desired and several coats of finish. It removes surface damage, most stains, and old coatings. It is also the operation that consumes wear-layer thickness, so any given floor can only go through it a limited number of times.; See also: Screen and Recoat, Wear Layer, Dustless Sanding
Screen and Recoat: Lightly abrading an existing finish with a mesh screen to give it tooth, then applying a fresh coat over the top. It renews a dulled or lightly scratched surface without touching the wood, so it consumes no wear layer and takes far less time than a full refinish. It cannot fix damage that has already gone through the finish into the wood.; See also: Sand and Finish, Wear Layer
Site-Finished: Wood flooring installed raw and then sanded, stained, and coated in place. Because the finish is applied after the boards are down, the surface is continuous across the whole floor with no bevel at the seams, and the color can be matched to the room. The trade-offs are dust, odor, cure time, and a house that is out of use while the work runs.; See also: Prefinished, Sand and Finish, Dustless Sanding
Wire-Brushed: A surface texture created by dragging stiff brushes across the board to scour out the softer earlywood and leave the denser latewood grain standing slightly proud. The result is a subtle linear texture that catches light, disguises small scratches and dust better than a smooth surface, and gives stains and reactive finishes something to sit in.; See also: Hand-Scraped, Prefinished

Category

Patterns & Formats

Chevron: A pattern of boards cut at an angle on both ends — forty-five degrees is the most common — so they meet point to point and form a continuous, unbroken V. Unlike herringbone, chevron needs purpose-cut boards, and the mitered joints leave little room for error: a small angular inaccuracy accumulates visibly across the length of a room.; See also: Herringbone, Parquet
Herringbone: A pattern of identical rectangular boards laid at right angles to one another, with the end of each board meeting the side of its neighbor to form a staggered, broken zigzag. The boards themselves are ordinary rectangles — the pattern comes entirely from the layout, which makes it labor-intensive and dependent on a carefully established working line.; See also: Chevron, Parquet
Parquet: Flooring assembled from small wood pieces arranged into a repeating geometric pattern rather than laid as continuous rows. It ranges from simple basketweave squares supplied as pre-assembled tiles to elaborate patterns cut and fitted on site. Parquet is generally glued down over a very flat substrate, since the pattern contains no long boards to bridge subfloor irregularities.; See also: Herringbone, Chevron, Glue-Down
Wide Plank: Flooring in noticeably wider boards than the narrow strip flooring that dominated mid-century construction. There is no single industry threshold, though boards wider than about five inches are commonly marketed this way. Wider boards show more of each piece's figure and put fewer seams in a room, and because each board moves more across its width, they raise the stakes on moisture control.; See also: Moisture Content, Plain Sawn, Engineered Hardwood

Category

Trim & Transitions

Reducer: A transition piece with a sloped profile, thicker on one side than the other, used where a thicker floor meets a thinner one — hardwood meeting sheet vinyl, for example. It brings the two surfaces together as a short ramp rather than a step, and it conceals the expansion gap along the taller floor's edge.; See also: Transition Strip, T-Molding
Riser: The vertical face between two stair treads. Risers take no foot traffic, so they are finished for appearance: painted, stained to match the treads, or clad in the flooring material. Their consistent height is a code-regulated dimension fixed when the staircase is framed, and it constrains how much material can be added on top of existing treads.; See also: Tread, Stair Nose
Stair Nose: The shaped trim that forms the front edge of a stair tread, overhanging the riser below and finishing the exposed end of the flooring. It takes the heaviest concentrated wear and impact of any piece on a staircase, so it is milled thicker than field flooring and is normally fastened and adhered rather than left to float.; See also: Tread, Riser, Transition Strip
T-Molding: A transition shaped like the letter T in cross-section, with a stem that drops into the gap between two floors and a cap that rests on both. It is used where two floors of roughly equal thickness meet, most often in a doorway, and it lets each floor expand and contract independently underneath the cap.; See also: Transition Strip, Reducer, Expansion Gap
Transition Strip: The general term for the milled or extruded piece that finishes an edge where one floor meets another, or where flooring meets a doorway, hearth, or exterior threshold. Beyond appearance it does real work: it covers the expansion gap, protects exposed board edges from chipping, and takes up any difference in height between the two surfaces.; See also: Reducer, T-Molding, Expansion Gap
Tread: The horizontal surface of a stair — the part you step on. Treads can be solid stair parts in a species matching the floor, or field flooring cut and applied over an existing structural tread and finished at the front with a stair nose. Because a staircase funnels traffic into a narrow path, treads wear faster than the floors they connect.; See also: Riser, Stair Nose

Category

Performance & Problems

Buckling: The extreme failure in which boards lift away from the subfloor, sometimes by several inches. It happens when a floor expands and has nowhere to go — a missing or filled expansion gap, a trapped perimeter, or a major water event. Buckling almost always requires lifting boards to relieve the pressure and correcting the underlying moisture or clearance problem.; See also: Expansion Gap, Cupping, Moisture Content
Crowning: The opposite of cupping — a board whose center sits higher than its edges. It most often appears when a cupped floor is sanded flat before the moisture that caused the cupping has left the wood. As the board finally dries and relaxes, the material removed from the high edges leaves the center standing proud.; See also: Cupping, Sand and Finish
Cupping: A distortion in which a board's edges sit higher than its center, forming a shallow trough across its width. It is a moisture problem rather than an installation defect: the underside of the board is wetter than the top, so the bottom swells. The fix is finding and correcting the moisture source and letting the floor dry — sanding a cupped floor before it dries makes matters worse.; See also: Crowning, Moisture Content, Buckling
Radiant Heat Compatibility: Whether a flooring product is approved for installation over a heated subfloor. Heat drives moisture out of wood from below, so compatibility depends on the product's construction — engineered and rigid-core products are approved far more often than solid wood — and on running the system within the manufacturer's stated maximum floor surface temperature, brought up gradually rather than all at once.; See also: Engineered Hardwood, Moisture Content, Acclimation

Category

Standards & Licensing

AC Rating: An abrasion-class rating for laminate flooring, defined by the European standard EN 13329 and running from AC1 upward, with higher classes indicating greater resistance to surface wear. The classes map to intended use, from light residential at the bottom of the scale through heavy commercial at the top. It rates the wear surface only — not impact resistance, moisture performance, or joint strength.; See also: Wear Layer, Mil (Wear Layer Thickness)
CSLB C-15 License: The Flooring and Floor Covering classification issued by the California Contractors State License Board. California requires a contractor license for construction work above a statutory dollar threshold, and C-15 is the specialty classification covering floor covering installation. Any active license number can be checked against the board's public lookup, which shows status, classification, bond, and workers' compensation coverage.; See also: AC Rating

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