Timber has long been used to build an attractive and practical addition to the home. A timber deck provides an area for relaxation and entertaining.
Sometimes a deck 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, a deck and its supporting structure are going to be exposed to the weather. It is essential that a suitable type of timber is chosen for the decking boards and for the supporting timbers. (See: Outdoor Timber)
Ideally, the timbers chosen should have a Natural Durability Rating of 1 or 2 in-ground contact or a rating of 1 or 2 outside above ground as appropriate (See: Natural Durability Ratings) or, alternatively, should be preservative treated timbers that have been treated to H3 or H4 as appropriate. (See: Treated Timber)
Generally speaking, treated pine decking 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 decking. 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. At the time of installation, gaps are provided between the decking boards to allow for expansion in the width of the decking 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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