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GLOSSARY OF TERMS
1″ 25.4 millimetres (mm)
1m 3.281 feet
1m3 35.315 cubic feet (cu.ft)
1m3 424 board feet (BF)
1MBF 2.36 cubic metres (m3)
AHEP American Hardwood Environmental Profile. Consignment-specific shipping document providing information to demonstrate the legality and sustainability of the U.S. hardwood species contained in that shipment including quantitative data on the environmental impacts associated with delivering it anywhere in the world.
BF Board feet
BM Board measure
Carbon footprint A summary of all the greenhouse gases emitted during the making process of an object and is expressed in kilograms of carbon dioxide equivalent (kg CO2eq).
Carbon sequestration During growth trees absorb CO2 from the atmosphere. Once trees are harvested and processed to produce sawn lumber (or any other wood product) they continue to store this CO2. This act of storing CO2 is referred to as sequestration.
Checks Longitudinal separation of the fibres in wood that do not go through the whole cross section. Checks result from tension stresses during the drying process.
Compressive strength The ability to resist a force tending to shorten a structural member by crushing the fibres longitudinally.
CLT Cross laminated timber
Decay The decomposition of wood substance by fungi (other terms: rot, dote).
Density Weight per unit volume. Density of wood is influenced by rate of growth, percentage of late wood and in individual pieces, the proportion of the heartwood.
Dimensional stability A term that describes whether a section of wood will resist changes in volume with variation in moisture content (other term: movement in performance).
Durability The resistance of wood to attack by decay fungi, insects and marine borers.
FAS The highest quality NHLA lumber grade.
FAS Foreign Agricultural Service
FIA Forest Inventory and Analysis programme. The FIA tracks the growth of individual American hardwood species each year, by county, across hardwood producing states in America.
Figure The pattern produced in a wood surface by annual growth rings, rays, knots, deviations from regular grain, such as interlocked and wavy, and irregular colouration.
Flitch A log or part of a log trimmed and prepared for conversion into veneers, or part of a converted log suitable for further conversion.
Glulam Glue laminated timber
Grain The direction, size, arrangement, appearance, or quality of the fibres in sawn wood. Straight grain is used to describe lumber where the fibres and other longitudinal elements run parallel to the axis of the piece.
Gum pocket An excessive local accumulation of resin or gum in the wood.
Hardness The resistance of wood against indentation and abrasion. Values are given in Newtons (N) and are a measure of the load required to embed an 11.3mm ball to one half its diameter in the wood.
Hardwood A description applied to woods from deciduous and evergreen broad-leaved 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.
Kilning The process of drying lumber artificially under scientifically controlled conditions. Kilns are the chambers used for this process.
LCA Life cycle assessment, usually environmental. A science based measurement system involving the collection of data on all the inputs and outputs of material, energy and waste associated with a product over its entire life cycle to calculate the environmental impact.
Lumber The American term for converted wood or sawn timber. Lumber mills and sawmills are terms used to describe the processing units that carry out this conversion.
m2 square metres
m3 cubic metres
Material replenishment A figure which represents the amount of time it takes for natural regrowth across the entire American hardwood forests, to replace the volume of harvested timber used in certain creative projects.
MBF Thousand board feet
Modulus of elasticity An imaginary stress necessary to stretch a piece of material to twice its length, compress it to half its length. Values for the individual species are given in megapascals (MPa – equivalent to N/mm2).
Modulus of rupture The equivalent fibre stress at maximum load. A constant used in structural design and obtained by loading pieces of wood to destruction.
Moisture content (MC) The weight of water contained in wood expressed as a percentage of the weight of the oven dry wood.
NHLA National Hardwood Lumber Association
PAR Planed (surfaced) all round (same as S4S)
Pith flecks Pith-like irregular discoloured streaks of tissue in wood, due to insect attack on the growing tree.
Quarter/rift sawn Lumber that is cut from the log on or near to the radial axis to produce edge, straight or vertical grain patterns.
RWL Random widths and lengths
S2S Surfaced 2 sides
S4S Surfaced (planed) four sides (same as PAR)
Sapwood The outer zone of wood in a tree, next to the bark. Sapwood is generally lighter in colour than heartwood but lacks resistance to decay.
Shrinkage The contraction of wood fibres caused by drying below the fibre saturation point (usually around 25-27% MC). Valves are expressed as a percentage of the dimension of the wood when green.
SM Surface measure
Specific gravity The relative weight of a substance compared with that of an equal volume of water. S.G. values given are based on wood volume at 12% MC and oven dry weight.
Split Separation of the fibres in a piece of wood from face to face (other term: end-split).
Stain A variation from the natural colour of the wood or a discoloration that may be caused by micro-organisms, metal or chemicals. The term also applies to materials used to impart colour to the wood.
Surfaced The American term that is used to describe lumber that has been planed.
Tally The American term for lumber measure. (Green tally refers to measurement before kilning and net tally to measurement after kilning.)
Tensile strength The ability to resist a force acting on a member and tending to lengthen the member or pull the fibres apart lengthwise.
Texture Determined by relative size and distribution of the wood elements. Described as coarse (large elements), fine (small elements) or even (uniform size of elements).
Warp Distortion in lumber causing departure from its original plane, usually developed during drying. Warp includes cup, bow, crook and twist.
Weight The weight of dry wood depends upon the cellular space, i.e. the proportion of wood substance to air space. Values are given for each species in kg/m3 at 12% MC.