| Term | Description |
| Green Certification | Landowners who actively manage their woods can apply for green certification. Two agencies perform reviews and issue certification for the Forest Stewardship Council (FSC): the non-profit Smartwood and the for-profit SCS (Scientific Certification Systems). Both agencies charge to ensure that land is properly and sustainably managed and that loggers employ best management practices (BMP) to cut wood on certified woodlots. To maintain its green certification status from landowner to consumer, lumber mills must also be certified in chain of custody arrangements, that is, they ensure that certified logs are stored and milled separately from non-certified logs. It was originally thought that certified logs would sell at a premium but that has not been the case in New England. The Quabbin Reservoir managed by the Metropolitan District Commission in Massachusetts was the first publicly owned land to be green certified. |
| Green lumber | Lumber with a moisture content in excess of 19%. |
| Green Lumber | Freshly cut lumber that has not had time to dry. |
| Green weight | The term green weight specifically refers to the weight of freshly harvested wood that has the same moisture content (MC) as the standing tree. MC is defined as the weight of water in the wood expressed as a percentage of the weight of the oven-dry wood (wood from which all moisture has beensd removed). Also see “dry weight.” |
| Green Wood | Freshly sawed or undried wood which still contains the moisture that was present in the standing tree. |
| Grillage | A system of orthogonal elements, usually beams or trusses, acting together to resist a common load. |
| Ground wood chips | Ground wood is usually produced from a hammer mill or tub grinder and appears shredded and fibrous with irregular sizes, depending on the screen or grate used. Ground wood is easily disinguished by its geometry from wood chips produced from mill chipper or a whole tree chipper (WTC). WTC and mill chips appear square and evenly cut rather than fibrous and irregular. |
| Ground wood paper | Newsprint and other inexpensive paper made from pulp created when wood chips are ground mechanically rather than refined chemically. |
| Growth Ring | The layer of wood growth formed by a tree during a single growing season. In many tropical species, annual growth rings are hardly discernible. |
| Growth rings | Rings of earlywood and latewood on the transverse section of a trunk or branch marking cycles of growth. |
| Gum | A natural exudation, also called kino, produced in trees as a result of fire or mechanical damage. |
| Gum | A generic term for non-volatile viscous plant secretions, which either dissolve or swell up in contact with water. |
| Gum Canal | Tubular intercellular cavities in hardwoods which may contain gums, mucilage, kinos, resins, or latex depending upon the genus. |
| Gum vein | A ribbon of gum between growth rings, which may be bridged radially by wood tissue at intervals. Also known as kino. |
| Gusset plate | Plates (1), often steel or plywood, fixed by nails, bolts or other means to connect timber members in a truss or other frame structure. Gusset plates may be applied to one or both sides of a joint. |
| Half-Blind Dovetail | A dovetail joint where the cut does not go all of the way through the board. The ends of a half-blind dovetail are concealed. |
| Hammer | A tool consisting of a metal head set perpendicular on a handle, used for driving nails. |
| Hardboard | A type of manufactured board similar to particle board but with a much smoother surface. A common brand of hardboard is Masonite. |
| Hardboard | A pressed homogenous fibreboard having a mean density of not less than 800 kg/sq m. |
| Hardboard | A generic term used to describe a panel produced mainly from interfelted ligno-cellulosic fibers (usually wood), consolidated under heat and pressure to a density of 31 pounds per cubic feet or greater, and to which other materials may have been added to improve specific properties. |
| Hardness | A property of wood that enables it to resist indentation. It is measure in kN and is often determined by the Janka hardness test. |
| Hardness | The property of wood that enables it to resist indentation by other materials. |
| Hardwood | A general term for timber of broad leafed trees classified botanically as Angiosperm. The term has no reference to the relative hardness of the wood. |
| Hardwood | Hardwood comes from deciduous trees that lose their leaves during the winter. Hardwoods have traditionally been used in making such products as furniture, strip flooring, interior trim, cutting boards, novelties, and so forth. Wood used in making these products is typically in the form of relatively small and defect-free pieces which are subsequently glued together; it is also generally more costly than wood from softwood species. Because of these factors, hardwood lumber is manufactured to non-standardized length and width dimensions which will minimize trim waste. For the same reasons, such lumber is measured relatively accurately, with rounding of measurements in small increments. |
| Headsaw | In a sawmill, the large band saw or circular saw used to size the log into lumber. |
| Heartwood | The wood making up the centre part of the tree, beneath the sapwood. Cells of heartwood no longer participate in the life processes of the tree. Heartwood may contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood. |
| Heartwood | In a cross section of a log, the heartwood is the center and dead portion where growth rings appear. Also see bark and sapwood. |
| Heartwood | The dead inner core of a tree. Usually much harder and darker than the newer wood. Also see sapwood. |
| Heartwood | The inner core of a woody stem or log, extending from the pith to the sap, which is usually darker in color. This part of the wood contains dead cells which no longer participate in the life processes of the tree. |
| Hectare | A metric unit of area, 100 metres by 100 metres (10,000 square metres) or 2.471 Acres. |
| Herringbone Pattern | In veneering, a hearing bone pattern is formed when successive layers of veneers are glued up so they form a mirror image. Usually this pattern slants upwards and outwards, like a herringbone. |
| Hewn timber | Timber with or without wane, finished to size with hand tools such as an axe or adze. |
| High-Grading | The practice of harvesting only the higher value trees and leaving the lower value trees in the woods (“Take the best and leave the rest”). It is frowned upon in this era of sustainability, and much effort is being made to find suitable markets for lower grade logs. |
| Hobnail | A pattern of pin-holes left by insect attack. |
| Honeycombing | A drying defect which occurs when tensile stresses in the core (usually a result of collapse) result in the formation of internal cavities. |
| Horizontally laminated timber | Laminated timber designed to resist bending loads applied perpendicular to the wide face of the laminations. For vertical loads, this means that the wide face runs horizontally. |
| Housed joint | A joint where one piece is notched or grooved to receive the other piece. |
| Hygrometer | An instrument for measuring the humidity of air. |
| Hygroscopic | Changes its moisture content to be in equilibrium with the atmosphere. |
| Hyperbolic paraboloid shell | A complex curved surface which has one line which is always straight. |
| Impact Strength | A strength property of wood that essentially measures energy absorption or work properties and toughness. |
| Improvement cutting | The removal of trees of undesirable species, form or condition from the main canopy of the stand, to improve health, composition and value of the stand. |
| Infeed | The direction a workpiece is fed into a blade or cutter. |
| Insulating Board | A generic term used for a homogeneous panel made from wood or cane fibers characterized by an integral bond produced by interfelting of the fibers, to which other materials may have been added to improve certain qualities, but which has not been consolidated under heat and pressure as a separate stage in the manufacturing process. The board has a density that is less than 31 pounds per cubic feet (specific gravity of 0.50) but greater than 10 pounds per cubic feet (specific gravity of 0.16). |
| Intensive silviculture | Refers to the treatments carried out to maintain or increase the yield and value of forest stands. Includes treatments such as site rehabilitation, conifer release, spacing, pruning, and fertilization. Also, known as incremental silviculture. Compare with basic silviculture. |
| Interlocked grain | Grain where the angle of the fibres periodically changes or reverses in successive layers. |
| Internal Stresses | Stresses that exist within a member even in the absence of applied external forces. |
| International Log Rule | In use since about 1906. Generally regarded as the most accurate of the three scaling methods, International log rule deducts only 2.12 Inches for slabs and 1/4 inch for kerf. (Also see Scribner and Doyle Rules.) It is the standard rule used in Massachusetts. |
| Irregular grain | Grain where the fibres contort and twist around knots, butts, curls and so on. Also called wild grain. |
| Isotropic | Exhibiting the same properties in all directions. |
| Jamb | The side of a window or door opening. |
| Jig | A device used to make special cuts, guide a tool, or aid in woodworking operations. |
| Joinery | Finished timber fixtures of buildings such as doors, windows, panelling, cupboards, etc. |
| Joint | A prepared connection for joining pieces of wood or veneer. |
| Joint group | Species of timber are classified into joint groups according to their mechanical properties. There are six joint groups for unseasoned timber (J1, the strongest to J6, the weakest) and six joint groups for seasoned timber (JD1 to JD6). |
| Joist | A structural framing member used horizontally to support a ceiling or floor. |
| Joist | One of a series of timber beams used to support the floor boards or ceiling of a building. |
| Just in time (JIT) | A buying philosophy characterized by minimizing inventories and buying products only as they are needed. |
| Juvenile spacing | A silvicultural treatment to reduce the number of trees in young stands, often carried out before the stems removed are large enough to be used or sold as a forest product. Prevents stagnation and improves growing conditions for the remaining crop trees so that at final harvest the end-product quality and value is increased. See also commercial thinning. |
| Juvenile Wood | Formed near the wood pith, it is characterized by progressive increase in dimensions and changes in cell characteristics, and the pattern of cell arrangement. It is also called core wood. |
| Juvenile wood | The term juvenile wood refers to wood formed early in the life of a tree. By most measures, juvenile wood is lower in quality than wood which forms later; this is particularily true of the softwoods. Juvenile wood is of greatest concern in lumber and other products in which wood is used in solid form. Juvenile wood is of lesser concern in paper and fiber products and in products in which wood is reduced to individual fibers, fiber bundles, or small pieces prior to product manufacture. The two most troubling characteristics of juvenile wood are that: 1) It shrinks and swells along the grain as moisture content changes; 2) Strength is lower, and in some cases much lower, than mature wood of the same tree |
| kerf | The cut made by a saw blade. |
| Kerf | The width of the sawblade (circular or band) and the source of sawdust. The more traditional circular sawblades are wider (1/4″ to 3/8″) than the newer band saw blades (1/8″ to 3/16″) and produce more sawdust, a waste byproduct of sawmills. |
| Kerfing | making a series of parallel saw cuts part way through the thickness of a piece of timber so that the piece can be curved towards the kerfed side. |
| Kickback | When a workpiece is thrown back, in the opposite direction the cutter is turning. |
| Kiln | A chamber used for seasoning timber in which the temperature and humidity of the circulating air can be controlled. |
| Kiln | A heated chamber used for drying lumber, veneer, and other wood products and in which air-flow, temperature, and relative-humidity conditions can be controlled. |
| Kiln | Freshly cut green lumber may be sold green or first 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. |
| Kiln | In lumber drying, a kiln is a room or building where temperature, moisture, and the amount of air circulating are controlled to dry wood. |
| Kiln Dried | Lumber that has been dried in a Kiln. |
| Kiln dried (KD) | Describes lumber that has been dried in a kiln (as opposed to being air dried). |
| Kiln dried after treatment (KDAT) |