A wooden house. Image credit designrulz.com

A wooden house. Image credit designrulz.com

ZIMSEC O Level Combined Science Notes:Timber properties and timber structures

  • Wood is a popular material in the construction industry
  • Wood is light and has a high strength/mass ratio
  • Light, strong beams/trusses are a priority in the building of houses
  • Wood is suitable for this type of structure because it is tough and flexible
  • Wooden beams are safer in a fire when compared to say steel beams provided the wooden beams are treated with fire retardant
  • This is because the wooden beams will only char but retain their shape and keep their position and much of their strength
  • A steel beam may expand and buckle tearing the building apart
Annual Rings. Image credit hobbithouseinc.com

Annual Rings of hardwood(left) and softer wood (right). Image credit hobbithouseinc.com

  • As trees grow they produce annual rings
  • These annual rings give the grain marks
  • They show where the tree’s very strong fibres laid down at various times in its life
  • Hardwoods grow at a slower rate and thus have annual rings that are closer together
  • The closer together the wood’s grain is the stiffer/ the wood is
  • Examples of hardwoods(close grains) are mukwa, mahogany and wattle
  • Softwoods (broad grains) include pines and poplar
  • They are usually lighter in color
  • Planks are cut longitudinally (along the length of the tree)
  • This is because the fibres of the tree are strong in tension
  • Cutting the tree across the grain would create weak spots and the planks would crack along the grain

To access more topics go to the Combined Science Notes page


Quick NetOne, Telecel, Africom, And Econet Airtime Recharge

If anything goes wrong, click here to enter your query.