Wood flooring has its own language. Some of the terms have to do with the appearance of the flooring, and those often are obvious. Some refer to technical aspects and are good to know when a contractor talks about how to make your wood floors perform well or how to fix those that need extra attention.
This list lays out some common definitions, a short glossary, of wood flooring terms.
Buckling, or the bulging upward of wood floors, happens when the flooring pulls away from the subfloor due to extreme moisture. This is a rare occurrence and usually happens after a floor has been flooded. If buckling floors are caught early, spot repair and board replacement might be possible.
Burls are a swirl or twist of the grain of the wood that usually occurs near a knot, but doesn’t contain a knot.
Character marks naturally occur in wood, such as burls, flags and flecks that give wood a unique appearance.
Cupping is when the edges of a wood floor board are high and the center of the board is low, creating a concave curve. The board curves in this way because of moisture trapped between the floor and the subfloor. High humidity often is the cause, but it can happen due to a water spill on the surface.
Crowning is similar to cupping, except it occurs when the boards’ bottoms eventually dry out and flatten, leaving the tops of the boards with a convex curve.
Flags are a heavy, dark mineral streak shaped like a banner.
Flecks are wide, irregular marks in quarter-sawn oak flooring.
Hardness has to do with the wood’s ability to resist indentation and abrasion. It’s measured by the load it takes to embed an 11.3 mm steel ball to half its diameter in the wood.
Hardwood often is used to describe any wood floor, but it refers to the woods that come from deciduous and evergreen broadleaved trees. It is not related to the hardness defined above. Hardwood species include oak, walnut and hickory. Species with needles and cones – e.g. pine, spruce and Douglas fir -- are softwoods.
Heartwood refers to the inner layers of wood in growing trees that no longer contain living cells. It usually is darker than sapwood. [Learn more about tree anatomy in “The Anatomy of Wood Flooring.”]
Mineral streaks are an accumulation of mineral matter from flow of sap. They appear as an unnatural color ranging from greenish brown to black.
Moisture content is the weight of water in wood expressed as a percentage of the weight of the oven-dried wood. [Learn more about moisture content and its effect on wood flooring in “Humidity Matters.”]
Pith flecks are irregular, discolored streaks of tissue in wood due to insect attack on the growing tree.
Sapwood is the outer area of wood in a tree, next to the bark. It generally is lighter than heartwood.
Shrinkage happens when the environment where the wood floor is installed gets too dry. The floor boards contract until a higher amount of humidity occurs, allowing the wood to reabsorb moisture and expand.
Shrinkage often happens seasonally in winter when air gets dryer, causing seasonal gaps between floor boards. Using a humidifier can help prevent or remedy seasonal gapping. Otherwise, the gaps will close when higher levels of humidity arrive in the spring.
Learn more about wood flooring in our Ultimate Guide to Hardwood Flooring or call us at 303-375-0280.