Timbers

Table of Contents

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1 Natural timbers: Hardwoods

  • comes from a tree with broad leaves
  • grow slowly and can take up to 100 years before they are ready to harvest
  • rarely planted so becoming scarse and expensive.

Oak

  • strong and durable
  • attractive grain
  • expensive
  • becoming rarer
  • not the easiest wood to work with
  • corrodes iron and steel
  • historically used for building houses and boat
  • more recently used for making high end furniture and wine/whisky barrels.

Mahogany

  • quite easy to work with
  • very attractive grain
  • expensive
  • environmental problems with sourcing from tropical forests
  • oils in the wood can cause skin rashes and breathing problems
  • used for making high-quality furniture, jewellery boxes and windows.

Beech

  • a tough wood
  • hard
  • does not crack or splinter easily
  • expensive
  • not very resistant to moisture
  • not suitable for exterior (outside) use
  • used for making toys, cooking implements, solid and laminated furniture.

Balsa

  • very light
  • easy to cut
  • much too soft and weak for most products
  • used for model making, surf board cores
  • historically used for rafts.

2 Natural timbers: Softwoods

  • come from tree with needle-like leaves and seeds in a cone
  • mainly evergreens
  • grow quickly, only needs 30 years before harvest
  • grown commericially
  • much cheaper than hardwoods

Here are some examples:

Pine

  • Very durable
  • Easy to work
  • Quite cheap as it grows quickly enough to be forested
  • reasonable strong, lightweight and easy to work with
  • can warp, crack and splinter more than some other woods
  • used for house construction in roof joists and floorboards
  • used internally for furniture and doors.

Cedar

  • Natural oils make it water and fungal growth resistant
  • not as strong and more expensive than pine
  • used for furniture, fences, shed and boats.

3 Manufactured timbers

  • by being manufactured there are no limitations to the size of boards available
  • changes the properties of the natural wood.

Here are some examples:

Plywood

  • Layers of tree trunk called veneer are glued together with the grain lines going in alternate directions
  • Flat, strong and looks like wood
  • Resistant to warping, cracking and twisting
  • quite expensive
  • edges can look rough
  • susceptible to water damage if the wrong grade is used. Marine ply is available
  • used for building and panels that need strength.

Medium density fibreboard (MDF)

  • wood dust and fibres are mixed with a glue and pressed into flat sheets under extreme pressure and heat
  • cheap as made from waste wood
  • smooth and ungrained so good for painting or staining
  • easily manufactured
  • needs coating as not very aesthic
  • weak compare to real wood or plywood
  • used for cheap flat pack furniture, wall panels, display cabinet and storage units.

4 Properties

Hardness

  • the ability to withstand cutting and scratching.
  • most timbers are soft and easily cut with metal tools
  • oak is quite hard for a wood
  • balsa is very soft for a wood
  • not to be confused with hardwoods and softwoods.

Toughness

  • the ability of a material to withstand being hit
  • a tough material can bend and deform without breaking
  • wood is a tough material as it can be dented with a hammer but not break.

Durability

  • the ability of a material to last a long time
  • if a wood has been properly dried and kept dry it can last for hundreds of years like oak beams in old buildings
  • wet wood can rot quickly and is not durable
  • some woods have natural oils which improve their durable abilities
  • can be treated with preservatives to make it more durable for external use.

5 Summary

  • Trees are divided into hardwoods and softwoods
  • different types of trees have different properties
  • knowledge of the properties of different timbers is important in choosing the best timber of the product
  • manufactured boards can be large flat sheets
  • hard, tough and durable are properties used for describing timber.

6 Exam questions

  • What is the difference between a hardwood and softwood?
  • What type of timber would you make a coffee table from? Give reasons why you think it is a good choice
  • What kind of things were often made from oak?
  • Why is beech a good wood for a child's toy?
  • Suggest a postive and a negative quality of MDF.