Glossary of Lumber terms
AIR DRIED (AD) Lumber that has been dried by exposure to air, usually in a yard, without artificial heat.
BEAM Any framing member placed to support a load.
BOARD FOOT (BD. FT. OR BF) The volume of a board 12″ long, 12″ wide, and 1″ thick or the equivalent (144 cubic inches of wood).
BURL A swirl or twist in grain of the wood, which usually occurs near a knot, but is not a knot.
CHECK A lengthwise separation of the wood that usually extends across the rings of annual growth and commonly results from stresses set up in wood during drying.
CONDITIONING The exposure of a material to the influence of a prescribed atmosphere for a stipulated period of time or until a stipulated relation is reached between material and atmosphere. Also referred to as “acclimating.”
CUP A distortion of a board in which there is a deviation from a straight line across the width of a board.
FIGURE The pattern produced in a wood surface by annual growth rings, rays, knots, deviation 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.
GRADE Term that defines the quality of the wood. The National Hardwood Lumber Association (NHLA) has set a standard grading scale. There are many criteria and restrictions, including number of cuttings, size of cuttings, and size of lumber.
GREEN Freshly sawn lumber, or lumber that has received no drying; unseasoned.
HARDWOOD Any close-grained wood from deciduous trees. Generally one of the botanical groups of trees that have broad leaves in contrast to the conifers or softwoods. The term has no reference to the actual hardness of the wood.
HEARTWOOD The wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood is generally darker than sapwood, but the two are not always clearly differentiated.
JANKA HARDNESS A scale that measures of the relative hardness of wood. The test measures the force required to push a steel ball with a diameter of 11.28 millimeters (0.444″) into the wood to a depth of half the ball’s diameter (the diameter was chosen to produce a circle with an area of 100 square millimeters). In the United States, the measurement is in pounds-force. It is one of the best measures of the ability of a wood species to withstand denting and wear. It is also a good indicator of how hard a species is to saw or nail.
KILN DRIED (KD) Lumber that has been dried in a kiln with the use of artificial heat; seasoned. Freshly cut green lumber may be sold green, air dried, or dried in a kiln to accelerate removal of the moisture in the wood. Drying wood in a kiln is an art to ensure that the wood dries evenly to retain its strength and aesthetic properties. Different species dry at different rates. Kiln dried lumber commands a higher price than green or air dried lumber.
LINEAR FOOT (LF) System of measuring length.
LUMBER Solid wood that has been sawn to a particular size. The product of the saw and planing mill not further manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching.
BOARDS Lumber that is nominally less than 2″ thick and 2″ or more wide. Boards less than 6″ wide are sometimes called strips.
NOMINAL SIZE As applied to timber or lumber, the size by which it is known and sold in the market often differs from the actual size.
ROUGH LUMBER Lumber that has not been dressed (surfaced) but which has been sawn, edged, and trimmed.
SHIPLAPPED LUMBER Lumber that is edge dressed to make a lapped joint.
SURFACED LUMBER Lumber that is dressed by running it through a planer. Lumber that is Surfaced Four Sides (S4S) means that all four faces of the board have been dressed. Boards can also be Surfaced One Side (S1S) or Surfaced Two Sides (S2S).
TIMBERS Lumber that is nominally 5″ or more in the least dimensions. Timbers may be used as beams, stringers, posts, caps, sills, girders, etc.
MILLWORK Building materials made of finished wood that have been specially manufactured.
MINERAL STREAK An olive to greenish-black or brown discoloration.
MOISTURE CONTENT (M.C.) The weight of water contained in wood expressed as a percentage of the weight of the oven dry wood. Most hardwoods in the United States are produced to standards developed by the National Hardwood Lumber Association (NHLA). No single moisture content, however, is specified for hardwoods because the uses are more specialized. The moisture content must be specified by the buyer and agreed to by the seller; a 10-12% moisture content specification is common.
MOULDING A trim piece of millwork used either strictly for decoration or for both decoration and to finish a joint.
OLD GROWTH A forest of mature or over mature timber that is beyond its peak growing period.
PIN KNOT A knot which does not exceed 1/8″ in average diameter.
PITH The small soft core occurring in the structural center of the log.
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.
PLYWOOD Sheets of wood consisting of three or more sheets of wood glued and bonded by heat and pressure with the grain of each sheet running perpendicular to adjacent layers.
PROFILE The shape of the wood, as seen from a side view.
QUARTER-SAWN Quarter-sawing means cutting a log radially (90-degree angle) 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 significantly. Quarter-sawn boards are popular for decorative applications.
RESAWING The process of sawing lumber in two lengthwise, parallel to the wide face. It is usually, though not always, done through the middle of the board, producing two equal sized boards, each approximately half the thickness of the original. Resawing changes the thickness of the lumber but not its width.
RIPPING The process of sawing lumber in two lengthwise perpendicular to the wide face. Ripping changes the width of the lumber but not its thickness.
SAPWOOD The living wood of pale color near the outside of the log.
SEASONING Removing moisture from green wood to improve its serviceability.
SHRINKAGE The contraction of wood fibers caused by drying below the fiber saturation point (usually around 25-27% M.C.). Values are expressed as a percentage of the dimension of the wood when green.
SOFTWOOD Any soft, light-textured wood of a coniferous tree.
SPECIES A commercial name assigned to tree.
SPLIT A lengthwise separation of the wood, due to the tearing apart of wood cells.
TONGUE-AND-GROOVE (T&G) A method of fitting similar pieces of wood together, edge to edge, used mainly with flooring and paneling. Each piece has a slot (the groove) cut all along one edge, and a thin, deep ridge (the tongue) on the opposite edge. The tongue projects a little less than the groove is deep. The tongue is inserted into the groove and thus two pieces fit together closely.
VENEER Thin sheets of wood of a specified thickness that are peeled, sliced, or sawn from logs for use in plywood, paneling and furniture.
WARP Warp is any variation from a true or plane surface. Warp includes bow, crook, cup and twist, or any combination thereof.
WEATHERING The mechanical or chemical disintegration and discoloration of the surface of wood caused by exposure to light, the action of dust and sand carried by winds, and the alternate shrinking and swelling of the surface fibers with the continual variation in moisture content brought by changes in the weather. Weathering does not include decay.
WOOD FLOORING Most wood flooring is made of hardwoods, such as oak, maple and pecan, as well as many other exotic imported species. Wood flooring can come in many sizes and varieties, including pre-finished or unfinished.
YIELD The proportion of the log converted into lumber.