3.1 Wood

• Sources of wood and the conversion of a log into timber
• Classification of wood into hardwoods and softwoods
• Structure of wood: bark, sapwood, heartwood, pith, growth rings and grain
• Properties of wood: strength, hardness, durability, workability and movement
• Common timbers used in Kenya and their uses
• Defects in timber: knots, warping, splits, insect and fungal attack
• Seasoning of timber by air drying and by kiln drying
• Selecting timber for a job, and conserving it

• explain the source of wood and how a log is converted into timber
• classify wood into hardwoods and softwoods
• identify the parts of the structure of wood
• relate the properties of a timber to the uses it suits
• identify common defects in timber
• explain the seasoning of timber
• select suitable timber for a given job
• appreciate the need to conserve wood as a resource

“How do we choose the right wood for a job?”

The titles are open to everyone. Reading a lesson needs an account — sign in or create one.

1. From tree to timber
   40 min · 1 practice tasks · quiz
   Fell, convert, season. Fifteen to forty years of growing, and one cut to waste it.
2. Hardwood and softwood
   40 min · 1 practice tasks · quiz
   The names describe the tree, not the timber. Balsa is a hardwood.
3. Inside a log
   40 min · 1 practice tasks · quiz
   Bark, sapwood, heartwood, pith and growth rings. Heartwood is the wood you want.
4. The properties that decide
   40 min · 1 practice tasks · quiz
   Strength, hardness, durability, workability and movement. Movement is the forgotten one.
5. Timbers you will meet
   40 min · 1 practice tasks · quiz
   Cypress, pine, grevillea, camphor, mvule, mahogany, neem, blue gum.
6. Defects in timber
   40 min · 1 practice tasks · quiz
   Bow, cup, twist, knots, splits and decay. Decay is the one that spreads.
7. Seasoning
   40 min · 1 practice tasks · quiz
   Green timber is half water. Stickers let the air reach every face.
8. Choosing wood, and making it last
   40 min · 2 practice tasks · quiz
   The job, the property, the timber, the board. Plant more than you cut.