Hardwoods come from broad-leaved, usually deciduous trees and include the densest, strongest, and most durable timbers. Some hardwoods contain resins or oils that interfere with paint hardening or include materials like silica that make working difficult. Softwoods are not necessarily softer, some can be very hard, and come from coniferous, mainly evergreen trees of the northern temperate zone. While hardwoods and softwoods refer to botanical classifications, not hardness, in general hardwoods tend to be denser and stronger for construction.

1. HARDWOODS & SOFTWOODS
o 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.

3. Cell structures of hardwoods and softwoods

4. TREE ANATOMY
CROWN
- 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

6. 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.

7. PROPERTIES OF TIMBER
PHYSICAL PROPERTIES
i. Bulk density
ii. Moisture movement
iii. Swelling
iv. Heat conductivity
v. Sound conductivity
vi. Resistance to action to acids and alkalis
MECHANICAL PROPERTIES
i. Compression strength
ii. Tensile strength
iii. Bending strength
iv. Shearing strength
v. Stiffness
vi. Toughness
vii. Cleavability
viii. Hardness

8. 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.