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Hardwood timber decking board installation

An Australian home just isn’t complete without an outdoor or ‘alfresco’ deck. But good design, installation and maintenance of timber decking is vital to ensure it looks great for many years after it has been installed. The information contained here sets out to address some design, installation and maintenance issues that, if ignored, can cause serious problems – principally, the premature deterioration of the timber deck boards.

A small mistake made when installing hardwood timber decking can lead to expensive rectification works down the track. The following measures, if adhered to, will help extend the life of hardwood timber decking boards and the subfloor structure. Note that this information is not intended to be used as an installation guide.

Exposure to weather

Hardwood timber decking boards will maintain their appearance and form for a long period of time if they’re covered by a roof. While this isn’t always possible, a timber deck that is covered can deliver enormous benefits to the home owner, namely:

  • The decking boards will not have to be re-oiled as often if the deck is protected from full exposure to the weather
  • As the boards won’t be exposed to full weather extremes they won’t expand and contract as much, thereby reducing the likelihood of timber splitting, warping, cupping, etc.
  • The deck will require less cleaning – fewer leaves and less dust will collect on the deck if the area is covered
  • A covered timber deck can be used all year round, which adds to the liveability of the home.

If the decking area cannot be covered it’s worth considering using narrower decking boards as they shed water more readily and will therefore be less prone to warping.

Installation of timber boards

Joist protection consists of rubber or other material placed on top of the joist, but under the decking board. This will help protect the joist from water ponding in the decking board gaps, which can lead to joists deteriorating prematurely. This is a fairly cheap product and will go a long way to protecting the joists and extending the life of the member. This is not a mandatory requirement, but is now almost standard practice in the industry.

Boards may be laid reeded side up or down, but don’t assume that installing the board’s reeded side up will mean that the grooves in the board will act as a non-slip surface. The grooves will collect dirt and grime if they are not cleaned vigilantly, causing them to become a slip hazard and leading to premature deterioration. It would be prudent to always lay hardwood timber decking with the reeded side down.

Decking board spacing is an important consideration, but there is no regulatory standard stipulating a definite figure. Timber industry groups will generally suggest a gap of 3mm for 90mm boards and up to 5mm for wider boards, but this is a suggested and nominal dimension. Installers will need to consider the timber species, the moisture content of the timber, climatic conditions and local experience when determining the distance between timber decking boards. Installing boards with larger gaps than suggested could create a trip hazard and installers should be wary of deviating from industry recommendations.

All surfaces of decking boards are required to be sealed with a water-repellent preservative or oil-based primer, plus one coat of the selected finish (this includes cut ends) prior to laying.

Predrilling of decking boards at butt joints is recommended with a suggested drill bit size approximately 80% of the diameter of the nails suggested.

The nails should be finished flush with the decking board surface and not punched as this can lead to premature deterioration of the decking boards. Installers should be particularly wary of this point when fixing decking boards with a nail gun.

Maintenance of the deck

Installers must make owners aware that they need to maintain their timber deck with regular cleaning such as sweeping and removal of garden debris. The use of a hose or a pressure cleaner should be discouraged.

Home owners must further be advised of the need to frequently reapply coatings to decking to prevent premature deterioration of the timber boards. The regularity with which the decks are recoated must be judged according to individual sitting conditions – differences in the amount of exposure to the weather will determine the regularity of maintenance required for a particular timber deck.


An outdoor hardwood timber deck can be a great entertaining area and serve the home owners for many years provided the deck has been designed and installed correctly, and regular maintenance is carried out.

For more information visit TABMA Australia or Timber Queensland

To find out more, contact HIA’s Building Services team.

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