The decomposition of wood by fungi.
A comprehensive guide to the most common timber terms from A to Z.
Decay
Decking
Timber used in surfacing parts of bridges and other structures subjected to vehicular or pedestrian traffic.
Degrade
In timber and other forest products, the result of any process that lowers the value of the wood.
Dehumidifier Kiln
A kiln working on the heat pump principle. Moisture evaporated from the timber by a flow of warm air is condensed on the evaporator coils of a refrigeration unit and drained away. The refrigerant is compressed and passed through condenser coils, re-heating the air stream.
Delamination
The separation of plies or laminations through failure of the bond, visible at an edge.
Density
As applied to timber, density is the mass of wood substance and moisture enclosed within a piece expressed in kilograms per cubic meter. As the mass will vary dependant on the amount of moisture in the piece, density is often expressed at a specified moisture content, usually 12%.
Depression
The difference between dry and wet bulb temperatures. It is a measure of humidity.
Dew Point
The temperature at which the relative humidity of a body of air is 100 per cent. Further cooling causes vapour in the air to condense as water droplets.
Diagonal Grain
Timber in which the annual rings are at an angle with the axis of a piece as a result of sawing at an angle with the bark of the log. A form of cross grain.
Diamonding
The change of a square or rectangular section timber to a diamond shape during drying. Diamonding occurs where the growth rings pass through diagonal corners of the section of the piece and is caused by the difference between tangential and radial shrinkage. It is a form of distortion.
Diaphragm
1. In a beam, an element at right angles to the span with the function of connecting the beams so that they resist load as a unit. 2. A relatively thin, usually rectangular, element of a structure that is capable of withstanding shear in its plane and acts as a bracing elements.
Diffusion
Movement of water through wood from points of high moisture content to points of low moisture content by molecular diffusion.
Diffusivity
A measure of the rate of moisture movement through wood by diffusion as a result of differences in moisture content
Dimension
Sawn - The nominal dimension of the board plus the overcut to allow for shrinkage. Nominal - The general intended size of the dry rough sawn board. Machined - The actual size of a machined or moulded board.
Dimensional Change
Changes in the size of a piece of dry timber as its moisture content changes to be in equilibrium with the surrounding atmospheric conditions.
Dipping
Submerging timber in a dipping vat containing fungicides or other chemicals to prevent stain or decay.
Discoloration
Change in the colour of wood caused by fungal or chemical stains, weathering, or heat treatment.
Distortion
A drying defect caused by the differential shrinkage along the three axes of a piece of wood. Distortion may take the form of cup, bow, twist, spring or diamonding.
Dowel
A cylindrical timber rod or steel bar generally without nut or thread driven into pre-drilled holes to make a joint.
Dowel Joint
A joint where the pieces of timber are joined by dowels running either longitudinally or transversely through the joint.
