Timber › Notes › 3.1 Timber: structure, properties, terms, defects

3.1 Timber: structure, properties, terms, defects

Tree structure: bark, phloem (carries food down), cambium (growth layer), sapwood (living, conducts sap, less durable), heartwood (dead, darker, more durable), pith; growth rings = earlywood (spring, lighter) + latewood (summer, denser); medullary rays.
Hardwood vs softwood: botanical, not hardness. Hardwoods = angiosperms (broad leaves, e.g. eucalypts such as Tasmanian oak, blackbutt, spotted gum, jarrah, ironbark; also imported merbau, maple, oak). Softwoods = gymnosperms/conifers (e.g. radiata pine, hoop pine, Douglas fir/Oregon). Red cedar dust is known to cause allergic reactions (2019 MC4).
Outdoor Australian hardwoods (2020 Q11): spotted gum, blackbutt, jarrah, ironbark, tallowwood (durable heartwood).
Properties: figure, grain direction, texture, colour, strength, durability, weight/density, hardness, weathering.
Terms: rough sawn; DAR = dressed all round (four machined faces); PAR (planed all round); nominal vs actual size; grades; lineal/linear metre; F-grades/MGP (stress grades); green vs seasoned; face side and face edge marks (2016 Q11).
Defects: splits, checks, shakes, knots, warping (bow, spring, cup, twist/wind), collapse, end splits.