Glossary
A comprehensive guide to the most common timber terms.
A pressed homogenous fibreboard having a mean density of not less than 800 kg/m².
The measure of a wood’s resistance to surface deformation, especially from localized pressure or impact. It’s an important property for flooring, furniture, and other wear-prone surfaces. The most widely used way to measure is the Janka Hardness Test.
Timber derived from deciduous or broadleaf trees (angiosperms), known for having a denser grain structure. It is typically strong and durable.
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.
Wood that has been manually cut and shaped, usually from a round log into a squared or flattened beam, using hand tools like axes, adzes, or broad hatchets.
- Large-headed nails used in heavy-duty timber fixing or decorative applications.
- May also describe a textured or studded finish on a surface (e.g., hobnail glass or decorative cladding patterns).
A drying defect which occurs when tensile stresses in the core (usually because of collapse) result in the formation of internal cavities.
Timber that is laminated layer by layer in a horizontal orientation (with laminations lying flat), bonded with structural adhesives to create a strong, stable composite element.
A joint where one piece is notched or grooved to receive the other piece.
A device for automatically regulating the relative humidity of air.
A general term for the presence of water vapour in air. There is a known limit to the amount of water vapour that air can hold at any particular temperature.
An instrument for measuring the humidity of air.
A hygroscopic material is one that naturally takes up and releases moisture from the air, seeking equilibrium with the ambient relative humidity.
A device for automatically regulating the equilibrium moisture content of the air. See also: Humidistat.
A hyperbolic paraboloid shell is a thin, curved structural form with a saddle shape, known for being strong, lightweight, and efficient—despite often being made from straight beams or timber members.
As applied to timber's moisture content, the tendency of dried wood to reach equilibrium with any specified temperature and relative humidity at a lower moisture content when absorbing moisture from a drier state than when losing moisture from a wetter state.