HARDWOODS & SOFTWOODSo These are botanical terms and do not always relate to hardness.

o Hardwood (angiosperms) are from broad-leaved trees most of which are deciduous, certain oaks and the majority of tropical trees are evergreens.o Hardwoods include the densest strongest and most durable timbers.o Some hardwoods contain resins and or oils which interfere with the hardening of paints and many such as teak include materials, eg: silica, which make working difficult.o The cheaper hardwoods approximate in cost to the more costly softwoods. o Softwoods (gymnosperms) are not all soft, some softwood are very hard.o Softwoods are all, for practical purposes, derived from coniferous trees which are mainly evergreens and grow chiefly in the Northern Temperature zone.

Cell structures of hardwoods and softwoods

TREE ANATOMYCROWN- Leaves, twigs, branches.- Water, carbon dioxide and mineral process to produce oxygen

TRUNK- As a backbone.- Annual ring to indicates maturity of tree

ROOTS- Acts as an anchor to the trees.- Absorb water and mineral

CHARACTERISTICS OF GOOD TIMBER

i. Narrow annual rings, closer the rings greater is the strength.

ii. Compact modular rays.iii. Dark colour.iv. Uniform texture.v. Sweet smell and shinning fresh cut surface. vi. When struck, sonorous sound is produced.vii. Free from defect in timber.viii.Heavy weight.ix. No wooliness of fresh cut surface.

PROPERTIES OF TIMBERPHYSICAL PROPERTIESi. Bulk densityii. Moisture movementiii. Swellingiv. Heat conductivityv. Sound conductivityvi. Resistance to action to acids and alkalis

MECHANICAL PROPERTIESi. Compression strengthii. Tensile strengthiii. Bending strengthiv. Shearing strengthv. Stiffnessvi. Toughnessvii. Cleavabilityviii. Hardness

TIMBER CONVERSION• The two main types of cuts are plain sawn and quarters sawn.• If the cut is such that the growth rings meet the surface at less than 45o then the timber is plain sawn. Timber with this type of cut tends to have a more decorative appearance but a greater tendency to distort by cupping.• Timber cut with the growth rings meeting the surface at not less than 45o is quarters sawn. Such timber is harder wearing, weather-resistant and less likely to flake.• If a log is cut through and through, which is most economical, then a mixture of plain and quarter-sawn timber is produced.