Glossary of Wood Terms

Air-dried or air-seasoned

Naturally seasoned in the open air, and generally protected from the sun and rain

Angiosperms (Angiospermae)

Botanical name for all plants whose seeds are carried inside an ovary, including what are commonly referred to as hardwoods: those trees which are broad-leaved, flowing and fruit-bearing. Most are deciduous.

Annual or growth rings

Concentric rings of wood added yearly to the growing tree in temperate zones.

Arboreal

Related to or connected with trees

Arboriculture

The management of trees, or groups of trees, for their amenity value

Adult or mature wood

Wood produced when the tree is already established; it will typically have a relatively constant cell size, stable physical behaviour and structural patterns that are well developed.

Back cut

The final cut when felling a tree, which is made on the opposite side to the direction of fall.

Backsawn

Sawn so that the growth rings are inclined at less than 45 degrees to the wide face. A backsawn log is converted in such a way as to provide the maximum number of cuts tangential to the growth rings

Bast

The soft, fibrous tissue between the bark and the inner cell structure.

Beating up

Replacing trees that have died soon after planting

Billets

Small-diameter round timber cut to length

Blaze

To mark a tree with paint or by slicing off bark with an axe, either to earmark it for felling or to delineate boundary lines

Board root

144 cubic inches of wood; for example, a board 12x12x1 in. Used chiefly in North America; elsewhere, cubic feet or cubic meters are preferred

Bole

The part of the trunk or stem of the tree from above the root butt to the first branch or limb, normally of timber size over 200mm in diameter

Bookmatching

The mirror-image effect obtained, especially in veneering, when adjacent sheets from a flitch are opened in the manner of a book, the back of one sheet being matched to the face of the next.

Box the heart

To leave a square piece at the heart when converting a log

Breast height

The point at which the girth or diameter of a standing tree is measured on the highest side; dbh = diameter at breast height. Breast height is normally regarded as 1.37m

Bucking

Cutting trees into shorter lengths such as logs and cordwood

Bummer

A truck for hauling logs

Butt

The base of a tree

Butt cut

The first cut above the stump of a tree

Butt log

The first log cut above the stump of a tree

Cambium

The layer of cells in a tree that divides to produce new tissue

Cheese block

A wedge to stop a log from rolling

Chromated copper arsenate (CCA)

The most frequently used preservative chemical for pressure-treating timber

Clean

Free of knots

Clear

Free from visible defects

Cleft

Split with an axe or similar tool rather than sawn (see also riven)

Clinometer

An instrument used for measuring slopes and the height of trees

Close-grained

Having narrow growth rings

Conversion

Sawing logs into smaller sections in preparation for use

Conversion loss

The difference between the volume of a standing tree and the volume of the boards cut from it. This is normally given as a percentage of the standing volume. Typical range: 8-20%

Coppicing

The practice of cutting down a woody stem to ground level to encourage growth of several stems from one root system. It is used with trees such as ash (Fraxinus spp.), Spanish chestnut (Castanea sativa), hazel (Corylus avellana) and willow (Salix spp.), whose stems are used for commercial purposes such as basket or hurdle making.

Cordwood

Low-quality, small-diameter wood suitable for pulp, firewood or chips

Corestock

The core layer or layers of wooden strips, plies, woodchips or particles used in manufacturing man-made boards such as block board, plywood and particleboard

Crosscut

To cut wood across the grain

Crown

The uppermost branches and foliage of a tree

Crown-sawn

A less common term for flat-sawn

Debarker

A sawmill machine that removes tree bark by chipping or grinding prior to sawing

Diameter at breast height (dbh)

See breast height

Dicotyledons (Dicotyledonae)

An order of plants within the Angiospermae that have two cotyledons or seed leaves. All hardwood trees are dicotyledons.

Diffuse-porous

(of a hardwood) having pores that are typically of uniform size throughout the growth ring

Earlywood

The first part of the annual ring, which is laid down in the spring, and typically has lower density and larger cells

End grain

The grain shown on a crosscut surface, revealing the cut ends of the wood fibres

End-rearing

Storing boards for seasoning vertically instead of horizontally; this can help reduce fungal staining, and is recommended particularly for European sycamore (Acer pseudoplatanus)

Equilibrium moisture content (EMC)

Wood is hygroscopic, and can therefore absorb or lose moisture at any time. When no water is being lost or given back, the moisture content is said to be in equilibrium. EMC is not a constant, but varies with temperature

Extractives

Substances, such as resins, deposited in the heartwood that giving its distinctive colour and odour. Extractives may affect the wood’s compressive strength, hardness, permeability, and resistance to decay and insect attack.

Exudates

Secretions such as gum, oil, latex or resin on the surface of timber. The amount of exudates can sometimes be exacerbated by kilning in some species.

Flatsawn

Cut tangentially to the growth rings; also referred to as crown-sawn

Flitch

A log or piece of wood prepared for conversion, especially into veneers. Also, a pack of about 500 pieces of veneer

Forwarder

A specialist tractor that extracts timber lifter clear of the ground

Fuming

A process for darkening woods that contain tannic acid by exposure to ammonia fumes in an airtight container before final finishing. The longer the exposure, the darker the wood will become. Due to its high level of tannic acid, oak (Quercus spp.) is especially suitable.

Genus

A group of closely related plants, sufficiently distinct not to interbreed. A genus normally consists of several species. The plural of genus is genera.

Girdling

The practice of cutting away the bark around the circumference of a tree before felling, so as the partially kill the tree and reduce moisture content.

Girth tape

A tape used to measure the diameter of a tree. The tape is placed round the girth but is calibrated in such a way that it gives a measurement of the diameter.

Grain

The arrangement of the fibres that make up the wood, or the pattern produces by these fibres on the surface of the wood. Many types of grain pattern are distinguished, such as fine, coarse, plain, interlocked, etc. The word grain tends to refer to the pattern of the wood, whereas figure refers to interesting irregularities. Timber species can be identified by their own unique, distinctive grain patterns.

Granny

An old tree – often European larch (Larix decidua) or Scots pine (Pinus sylvestris) – surrounded by young trees growing vigorously

Green tonne

A unit of measurement of freshly felled timber before any drying

Green wood

Freshly cut wood that is not seasoned or dried and is still ‘wet’

Gymnosperms (Gymnospermae)

The conifers and related plants, whose seeds are not contained without an ovary; they have needle-like leaves, and produce the softwoods.

Hardwood

Wood from a broad-leaved (dicotyledonous) tree – usually harder than softwood, but not always

Harvester

A forestry machine that cuts a tree from its root, de-branches it and then cuts it to lengths

Heartwood or true wood

The non-functioning xylem tissue toward the centre of the trunk, which provides the hardest and most durable part of the timber

Hewn timber

Timber finished to size with an axe

Hypsometer

An instrument used from ground level to measure the height of trees. A clinometer is a type of hypsometer.

Interlocked grain

Grain that exhibits periodic changes in the direction and pitch of the fibres, often producing a ribbon-like figure.

Juvenile wood

Wood produced in the first years of growth, up to about five years. Juvenile wood is normally of lower strength, has thinner cell walls and higher lignin content than mature wood

Kerf

The cut made by a saw blade; also, the width of this cut

Lammas growth

A second spurt of growth in late summer in some tree species, such as oak (Quercus spp.)

Latewood

The filling of an open-grained wood – typically oak or ash (Quercus, Fraxinus spp.) – with lime slurry, which leaves a milky-white colour in the filled pores for decorative effect. Nowadays ‘liming wax’ is usually substituted

Longitudinal shrinkage

Shrinkage along the grain, resulting in the shortening of the wood during drying; this is usually minimal

Mallee

A shrubby form of eucalyptus (Eucalyptus spp.) that grows in the desert regions of Australia

Medullary rays

Vertical ribbons or sheets of tissue formed radially across the annual rings, which are very distinctive in some woods, such as oak (Quercus spp.), and barely visible in others

Moisture content (MC)

The moisture content of wood decreases dramatically during seasoning. The completely dry (oven-dry or kiln dried) weight of a given species is a constant, and the moisture content of the wood at any given time can be express as a percentage of this constant. The formula: MC = weight of water present in sample / oven-dry weight of sample * 100

Movement (or wood movement)

A general term to describe shrinkage and distortion due to stresses or water loss in the wood. This varies considerably between timber species and dependant on the conditions that the wood is exposed to.

Old growth

Forest or wood with trees regenerated by natural succession, containing a substantial number of old trees and some dead wood. Old growth is often preferred to less mature timber, but there is a negative ecological result of harvesting too much old-growth wood.

Oven-dry weight

The weight of a piece of wood which has been dried in a kiln until there is no further weight loss

Palmate leaves

Leaves whose lobes are arranged like the fingers of a hand

Pedunculate

(of fruit) borne on a stalk

Phloem

The inner bark, used for food transport in the growing tree

Pith

The soft core in the centre of a tree trunk, branch or twig

Plainsawn

Same as flatsawn

Pluck-out or pull-out

A blemish in wood that has been caused by a tool pulling a clump of fibres away from the body of the wood; this can occur with part-decayed or decayed wood.

Pollarding

The lopping of tree branches at head height or above, either to encourage shoots to form higher up a tree out of reach of browsing animals, or simply to reduce the size of a tree.

Prime

The best quality of timber

Pulpwood

Wood suitable for manufacturing paper

Quartersawn

Cut radially from the bark to the heart, often producing ribbon figure

Refractory wood

Wood that is difficult to dry, machine, process using conventional methods, and impregnate with preservatives

Regrowth

Trees that have grown within a forest after the older or original trees have been felled or removed

Ring-porous

Having more conspicuous pores in the earlywood than in the latewood

Rip

To cut along the grain

Rip cut

A cut made parallel to the grain

Riven

Similar to cleft, but refers specifically to the splitting of wood into small sections such as traditional plasterers’ laths.

Roundwood

Small branches and logs

Sanitation cutting

Removing deceased or damages stems to prevent the spread of insects or disease.

Sapwood

The relatively soft and perishable wood from the outer part of the trunk; a non-technical term for xylem

Sawlogs

Timber of typically 140mm diameter or more at the small end, which can be sawn economically into planks and boards

Sensitizer

Any wood (or other substance) which, after initial exposure, will invariably cause an allergic reaction in the user when encountered again. This may take form of dermatitis, other skin disorders, or respiratory and associated problems. Yew (Taxus baccata), for example, can be a sensitizer for some woodworkers.

Silviculture

The cultivation of forest trees to produce wood products

Skidder

A tractor used to drag logs out of the forest

Snedding

Removing branches from a felled tree

Softwood

Wood from a coniferous (gymnosperm) tree – usually softer than hardwood, but not always

Species

A subdivision of genus; a group of individual plants of the same kind that share many of the same characteristics. The genus Quercus encompasses all types of oak, whereas Quercus robur is the name of one particular species of European oak.

Sticks or stickers

Pieces of wood of uniform size placed between stacked boards to aid drying and give support. They should be of a neutral wood that will not stain the boards.

Sweep

A long, gentle, natural bend in a log or tree

Tangential shrinkage

Shrinkage at right angles to the grain, that could cause cupping on flatsawn wood

Wolf or wolf tree

A larger than average, old tree with a spreading crown and limited timber value, though often a great value to wildlife

Woolly grain

A woolly or fuzzy surface with frayed, rather than cleanly cut fibres, after machining. It can occur with tension wood, or can be a feature of certain species.

Xylem

The living tissue in the outer layers of the tree trunk, serving to transport sap and store food; known as sapwood when converted to timber.