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.

HARTWOOD EN SAPWOOD

Within each tree there will always be two types of wood found Heartwood and 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

IMPORTANT INFORMATION

• Do not burn preserved wood.
• Wear a dust mask and goggles when cutting or sanding wood.
• Wear gloves when working with wood.
• Some preservative may migrate from the wood into surrounding soil/water or many dislodge from the preserved wood surface upon contact with skin. Wash exposed skin areas thoroughly.
• All sawdust and construction debris should be cleaned up and disposed of after construction.
• Wash work clothes separately from other household clothing before re-use.
• Preserved wood should not be used where it may come into direct contact or indirect contact with drinking water, except for uses involving incidental contact such as fresh water docks and bridges.
• Do not use preserved wood under circumstances where the preservative may become a component of food, animal feed, or beehives.
• Do not use preserved wood for mulch.
• Only preserved wood that is visibly clean and free of surface residue should be used.
• Use fixings, hardware or any metal products as recommended by their manufacturer.
• If wood is to be used in an interior application and becomes wet during construction, it should be allowed to dry before being covered or enclosed.
• Disposal Recommendations: Preserved wood may be disposed of in landfills or burned in commercial or industrial incinerators or boilers in accordance with National and Regional regulations.
• Use fixings and other hardware which are in compliance with building regulations for the intended use.
• Mould growth can and does occur on the surface of many products, including preserved or untreated wood, during prolonged surface exposure to excessive moisture conditions. To remove mould from preserved wood surfaces, wood should be allowed to dry. Typically, mild soap and water can be used to remove surface mould.

USE AN END COAT PRESERVATIVE

Any surface exposed by drilling or cutting must be coated with a cut end preservative. Failure to coat will affect the value of the preservative. 

It is recommended that the coated ends are not put in the ground or in direct contact with water. Rip sawing, thicknessing and planning are not permitted unless the wood is subsequently processed to the original specification. 

THE RIGHT FIXINGS

When working with preserved wood, it is important that you use the right fixings. Use fixings, hardware or any metal products as recommended by their manufacturer.

It is good practice to drill pilot holes for fixings when screwing near the edge or end of a piece of wood. 

Preserved wood can be glued with most commonly used adhesives once dry (see Technical Data sheet for further details). 

APPLYING A FINISH

If you desire to apply a finish to your preserved wood, we recommend use of oil-based penetrating finishes that are transparent or semi-transparent. 

We do not recommend using paint or other film-forming finishes because long term maintenance of these finishes can be problematic. Whatever finish you use, always check the label of the finishing product and follow the manufacturer’s instructions. Some water repellents and semi-transparent stains can be applied to preserved wood soon after construction. Paint manufacturers generally recommend waiting up to one year before applying a paint product to preserved wood. Apply the finishing product to a small exposed test area of your project before finishing the entire project. 

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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