Glossary
Wood & timber terms, explained
The vocabulary of wood — defined clearly so you can read spec sheets, compare species and brief suppliers with confidence.
- Air-Dried
- Timber seasoned by exposure to air rather than a kiln, typically reaching a higher moisture content than kiln-dried stock.
- Block Board
- An engineered panel with a core of solid wood battens between veneers, resistant to bending over long spans — used for shutters and long shelves.
- Burr / Burl
- A highly figured growth on a tree producing swirling, knotty veneer prized for decorative work.
- BWR / BWP
- Boiling-Water-Resistant / Boiling-Water-Proof plywood, bonded with phenolic adhesives for damp areas like kitchens and bathrooms.
- Chain of Custody
- Documentation tracing timber from a certified forest through every stage of processing and trade to the final product.
- Checking
- Small cracks that develop along the grain as wood dries unevenly, usually at board ends or surfaces.
- CITES
- The Convention on International Trade in Endangered Species, which regulates or restricts trade in certain timber species to protect them.
- Cooperage
- The craft of making barrels and casks — traditionally from watertight white oak.
- Decay Resistance
- How well a wood resists fungal rot, especially in damp conditions — a key factor for exterior and ground-contact use.
- Density
- The mass of wood per unit volume (kg/m³ at a stated moisture content); a strong indicator of strength, hardness and weight.
- Dimensional Stability
- A timber's ability to resist changes in size and shape as humidity and temperature vary. More stable woods move less and stay flatter.
- Durability (Natural)
- A heartwood's inherent resistance to decay and insect attack, often rated from 'very durable' to 'perishable'. It does not include treated timber.
- Engineered Wood
- Manufactured wood products (plywood, MDF, block board, engineered flooring) made by binding wood fibres, veneers or particles for performance and stability.
- FEQ
- First European Quality — a premium teak grading denoting clear, defect-free, uniformly coloured timber.
- Figure
- Distinctive decorative patterns on a wood surface caused by grain, growth rings, rays or knots — e.g. fiddleback, bird's-eye or quilted figure.
- FSC
- Forest Stewardship Council — an international certification verifying that wood comes from responsibly managed forests, tracked via chain of custody.
- Grain
- The direction, arrangement and appearance of wood fibres. Grain can be straight, interlocked, wavy or irregular, affecting both looks and workability.
- Hardwood
- Timber from broad-leaved (angiosperm) trees such as teak, oak and walnut. 'Hardwood' refers to the botanical type, not necessarily physical hardness.
- Heartwood
- The dense, non-living inner wood of a tree. It is usually darker, more durable and more decay-resistant than the surrounding sapwood.
- Interlocked Grain
- Grain in which fibre direction alternates between growth layers, producing a ribbon figure but a tendency to tear during planing.
- Janka Hardness
- A standard measure of a wood's resistance to denting and wear, expressed in pounds-force (lbf) or newtons (N). Higher values mean a harder, more dent-resistant timber.
- Kiln-Dried (KD)
- Timber dried in a controlled kiln to a target moisture content for stability, reducing the risk of warping, shrinking or cracking after manufacture.
- Laminate
- A hard surfacing sheet of resin-impregnated papers fused under heat and pressure, applied to panels for a durable, decorative, easy-clean finish.
- Log
- A full, unsawn section of tree trunk, traded for milling into timber or veneer.
- MDF
- Medium-Density Fibreboard — a dense, uniform panel of fine wood fibres bonded under heat and pressure, with smooth faces ideal for painting and machining.
- Modulus of Elasticity (MOE)
- A measure of a wood's stiffness — its resistance to bending under load, expressed in GPa. Higher MOE means a stiffer timber.
- Modulus of Rupture (MOR)
- A measure of a wood's bending strength — the stress it can withstand before breaking, expressed in MPa.
- Moisture Content (MC)
- The weight of water in wood as a percentage of its oven-dry weight. Furniture-grade timber is usually dried to 8–12% MC.
- Movement
- The expansion and contraction of wood as it gains or loses moisture. 'Small movement' woods are more stable in service.
- MR Grade
- Moisture-Resistant grade plywood suitable for dry interior use, bonded with urea-formaldehyde adhesives.
- Plain-Sawn (Flat-Sawn)
- The most common and economical cut, producing the familiar 'cathedral' grain pattern but with more movement than quarter-sawn boards.
- Plywood
- An engineered panel of thin wood veneers glued with grain directions alternating (cross-bonded) for strength and dimensional stability.
- Quarter-Sawn
- Boards cut so the growth rings meet the face at 60–90°, producing straight grain, greater stability and (in oak) dramatic ray flecks.
- Rift-Sawn
- Boards cut at an angle that yields very straight, consistent grain with minimal flecking — favoured for a clean, uniform look.
- Sapwood
- The younger, living outer layers of wood that transport sap. It is typically paler, softer and less durable than heartwood.
- Sawn Timber / Lumber
- Wood that has been cut from logs into boards or sections of standard or custom dimensions.
- Seasoning
- The controlled drying of timber (air or kiln) to a stable moisture content before use.
- Shrinkage
- The reduction in a wood's dimensions as it dries, measured radially, tangentially and volumetrically. Uneven shrinkage causes warping.
- Softwood
- Timber from coniferous (gymnosperm) trees such as pine and spruce. Generally lighter and faster-growing than hardwoods.
- Specific Gravity
- The density of wood relative to water. Higher specific gravity generally indicates a heavier, harder and stronger timber.
- Thermo-Treated Wood
- Timber heated to high temperatures to improve dimensional stability and decay resistance without chemicals — used for cladding and decking.
- Treatability
- How readily a wood absorbs preservative treatment. Many durable heartwoods (teak, Ipe) resist treatment because they don't need it.
- Tyloses
- Bubble-like growths that block the pores of some hardwoods (e.g. white oak), making them watertight and suited to outdoor and cooperage use.
- Veneer
- A thin slice of real wood (typically ~0.5 mm) bonded to a substrate to give the appearance of solid timber economically and stably over large surfaces.
- Warping
- Distortion of a board (cup, bow, twist or crook) caused by uneven drying or moisture changes.
- Workability
- How easily a wood can be cut, shaped, glued and finished with hand and machine tools.
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