Glossary of Hardwood Flooring Terms

Character Marks
Naturally occurring marks in the wood, such as burls, flags and flecks, that give a unique appearance.

Check
A lengthwise separation of the wood that usually extends across the rings of annual growth and commonly results from stress set up in wood during air or kiln drying.

Dimensional Stability
A term that describes whether a section of wood will resist changes in volume with variation in moisture content.

Engineered Wood Flooring
A hardwood flooring made of a top wear layer of hardwood which can be sanded and finished and a lower portion of a cross laminate ply making the board dimensionally stable.

Figure
The patter produced in a wood surface by annual growth rings, rays, knots, deviations from regular grain, such as interlocked and wavy, and irregular coloration.

Grain
The direction, size, arrangement, appearance, or quality of the fibers in sawn wood. Straight grain is used to describe lumber where the fibers and other longitudinal elements run parallel to the axis of the piece.

Hardness
Generally defined as resistance to indentation using a modified Janka hardness test, measured by the load required to embed a 0.444 inch ball to one-half its diameter.

Hardwood
A description applied to woods from deciduous broad-leafed trees (Angiosperms). The term has no reference to the actual hardness of the wood.

Heartwood
The inner layers of wood in growing trees that have ceased to contain living cells. Heartwood is generally darker than sapwood, but the two are not always clearly differentiated.

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

Moisture Content (M.C.)
The weight of water contained in wood expressed as a percentage of the weight of the kiln dried wood.

Plain-Sawn
Plain-sawn hardwood boards are produced by cutting tangentially to a tree’s growth rings, creating the familiar flame-shaped or cathedral pattern. This method also produces the most lumber from each log, making plain-sawn lumber a cost effective design choice. Plain sawn lumber will expand and contract more than boards sawn by other methods. Wood stamped plain sawn can contain any combination of the following types of grain classification: plain sawn, rift sawn, and quarter sawn.

Quarter-sawn
Quarter-sawing means cutting a log perpendicular to the growth rings to produce a vertical and uniform pattern grain. This method yields fewer and narrower boards per log than plain sawing, boosting their cost. They will expand and contract less than boards sawn by other methods and are one of the few solid boards you can put down over radiant heat. NOFMA quartered characteristics include at least 50% of piece must contain quartered characteristics (in cross section the angle of the annual ring tangent to the face of the piece to be between 45 degrees and 90 degrees.)

Rift-sawn
Rift-sawing at a 30-degree or greater angle to the growth rings produces narrow boards with accentuated vertical or straight grain patterns. NOFMA rift characteristics include at least 75% of the piece must contain rift characteristics (in cross section the angle of the annual ring tangent to the face of the piece to be between 30 degrees and 60 degrees.)This type of lumber is available in limited quantities and species.

Sapwood
The outer zone of wood in a tree, next to the bark. Sapwood is generally lighter than heartwood.