An attractive and practical method of cladding a home is to use timber in either sheet form (such as plywood) or in the form of specially profiled boards. Plywood sheeting used for cladding a wall sometimes has a surface which is smooth and sometimes has a surface which has been decoratively grooved. The specially profiled boards are generally referred to as cladding or weatherboards but are also referred to as chamfer boards or siding.
The boards are profiled to overlap to keep out the weather and depending on the profile, may be fixed horizontally, vertically or at an angle.
 There are a number of profiles produced. The various profiles not only govern how the boards may be fixed, but offer a range of visual impacts. Profile descriptions include rusticated, feather-edged, chamfered, single log cabin and double log cabin.
Cladding is a specialty timber product. Specialty timber products (sometimes referred to as milled products) include products that may have either a sawn or dressed surface and are graded primarily for appearance although some do have a strength requirement. They include flooring, cladding, lining boards, joinery products and domestic decking. There are several grades described in Australian Standards and a range of standard sizes and profiles available. (See:
Sawn or Milled Timber).
Sometimes cladding does not live up to user expectations. In most cases this is not the fault of the material but rather as a result of a lack of understanding of the various species of timber, their suitability and their installation and maintenance.
Generally speaking, cladding is going to be exposed to the weather. It is essential that a suitable type of timber is chosen.
Ideally, the timbers chosen should have a Natural Durability rating of 1 or 2 outside above ground (See: Natural Durability Ratings) or, alternatively, should be preservative treated timbers that have been treated to H3 (See: Treated Timber).
Generally speaking, treated timber cladding is a timber product that has been treated with a preservative to improve the timber's resistance to attack by wood destroying fungi and wood destroying insects. In other words, the timber's durability is enhanced to a level which is suitable for use as cladding. However, the "treatment" does not afford the timber protection against weathering.
When any timber (treated or untreated) is exposed to the weather, the timber will take up and lose moisture from or to the atmosphere as the environment around the timber changes on daily or seasonal basis. The timber will expand or contract when it takes up or loses moisture. The profile and the method of fixing of cladding allow for expansion in the width of the cladding boards during periods of higher humidity.
As a result of taking up and losing moisture, the timber will develop surface checking. The severity of the checking will depend on the timber species, the rate at which the moisture content of the timber changes and how long that moisture content is maintained before it changes again.
The application of a protective coating to the timber surface will minimise the effects of weathering of any timber (treated or untreated) in an exposed situation. The purpose of the protective coating is to slow down the rate at which the timber will take up or lose moisture. By slowing that rate down, the severity of any checking is considerably reduced.
Protective coatings include products which penetrate the surface of the timber and products which provide a film or coating to the surface of the timber.
In many parts of Australia, the construction of new buildings and additions to existing buildings will be assessed as being in a Bushfire Prone Area. The relevant Australian Standard - AS 3959 - provides for a range of Bushfire Attack Levels for proposed construction. Each Level is based on the assessed threat and as the assessed threat increases, so do the restrictions on the building materials that may be used. Where there are restrictions on the building materials, timber is permitted in the lower levels provided the timber species meets certain criteria. (See: Construction in Bushfire Prone Areas).
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