Timber
Timber
Timber
Wood has been historically used as a construction material and these buildings have lasted a long
time. Wood was naturally durable because it came from ‘old’ slow growing trees with high heart
wood content.
Today faster growing species have a higher sap wood content.
WOOD AS A NATURAL RESOURCE
Wood is a renewable natural resource with many advantages to the construction industry. It is
attractive, easy to use and very strong for its weight.
WHAT IS WOOD?
Wood is a cellular material of biological origin, it is:

Hygroscopic - This means it can both take on and lose moisture from the air in its environment

Anisotropic - This means that its structure and properties vary in different directions

Therefore, the fundamental structure of wood, determines the properties and behaviour of a
species.
HARDWOOD & SOFTWOOD
Most people get confused about the term’s hardwood and softwood. It has nothing to do with how hard or soft they are. The distinction is a botanical one linked to the similarity in species cell structures.

Softwoods tend to grow in colder climates and has thin narrow leaves like needles. An example would be Pine.

Hardwoods tend to grow in ambient temperate, if grown in warmer climates trees have broader leaves.

The best way to distinguish hardwoods from softwoods is by the cell structures. Softwoods have more open cell structure called tracheid’s or vessels. Hardwoods cell structures are called fibres.
HEARTWOOD AT SAPWOOD
The Sapwood is the live part of the tree that transports water and nutrients from the roots to the
leaves. The Heartwood is the area where unwanted extractives are stored. These extractives make
the Heartwood naturally durable.

The Sapwood zone is the area that we need to protect with wood preservatives.
Chemical Composition of Wood

Dry wood is composed (subject to species)
• Cellulose 50% (Sugars)
• Hemi-Cellulose 15% (Sugars)
• Lignin 30% (Fibre)
• Eraneous Extractives 5% (Resins)
THE HYGROSCOPIC NATURE OF WOOD
All wood in growing trees contains a considerable amount of water. Water is required as part of the growth processes. This water is commonly called sap.
Water in wood is either known as:
• Free – inside the cell cavity
• Trapped or Bound – Inside the cell walls

The amount of water in wood expressed as a percent of the dry weight is called the “Moisture Content”
As wood dries the Free water is the first to be removed. Once the Free water has been removed timber is known as being at Fiber Saturation Point (FSP). Once below this point the trapped water begins to be removed and timber will begin to shrink.

This is a very important stage and because wood is anisotropic shrinkage can occur in different
directions. This can cause defects if not controlled. If drying below FSP is controlled, then the timber
can have improved strength properties.

Timber should be dried at a controlled rate below FSP before it is preserved.
WOOD PRESERVATION
Sapwood needs protecting and a commercial way of achieving this is with wood preservatives. This will improve the service life of modern high Sapwood timbers and reduce ecological pressures on the Forests. 
Wood needs protecting from fungal decay organisms and wood destroying insects and termites who see wood as a home or a food source. 

Many preservative systems are available and they can be applied by industrial pressure applications or by brush. 

Applied correctly and to standards levels of service life can be achieved. 

It is always important to ensure that the right preservative system and application is employed to suit the service life requirement. 

Preserved wood when fully dry is safe to use when used as directed. 

To ensure your personal health and safety it is best to follow the precautionary information provided by the manufacturer when handling treated wood. 
Generally, you should: 
• Always adopt good work practices
• Wear suitable protective clothing, gloves and if dust is generated, wear eye and respiratory protection.
• After use and before eating and drinking, wash hands.
• Sawdust may accumulate on clothing / wash work clothes before reuse
WOOD VS OTHER CONSTRUCTION MATERIALS – SOME INTERESTING FACTS
  • It takes 21 times more energy to produce a concrete slab floor than a raised wood floor
  • Producing concrete emits up to 3 times more carbon dioxide, carbon monoxide and hydrocarbons than manufacturing lumber.
  • Wood has 8 times greater insulating capabilities than concrete.
  • It takes 5 times more energy to produce aluminum siding than wood siding.
  • Producing aluminum generates 8 times more air emissions and 300 times more water emissions than lumber
  • Wood has 2,000 times greater insulating capabilities than aluminum.
  • Aluminum requires large amounts of energy to recycle.
  • It's estimated we'll run out of bauxite, the main ingredient in aluminum, in less than 200 years
  • Plastic is made from non-renewable petrochemicals.
  • Plastic is not biodegradable. It remains in its current form for at least 500 years.
  • Plastic recycling requires toxic chemicals that can make the process dangerous and costly
  • It takes 9 times as much energy to produce a steel stud than a wooden one.
  • Steel consumes 4,000 times more coal, gas and oil to mine and produce than wood.
  • Processing steel releases 15 times the sulfur dioxide and 27 times the nitrous oxide than wood.
  • Steel requires 25 times more water to manufacture than wood.
  • Gas and oil emissions used in steel processing have increased by over 500% since 1950.
  • Wood has 413 times greater insulating capability than steel.
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