Expert Advice
Frank DiStefano

Choose the right timber

There are many properties in timber that can influence us when making decisions as to which one we choose. Properties like strength, durability, dimension stability, moisture content and appearance should all be considered.

The best choice will always be the timber that has the properties that best fit the required purpose.

Hardwood timber with durable properties could be selected for external use where it is exposed to harsh conditions. This same timber species could also be chosen for an internal application, like a feature wall, because of its appealing grain and colour properties.

Janka Rating

One particular property of timber is its Janka. This is the measurement in kN used to rate the hardness and density in timber and shows its resistance to denting. A higher Janka rating for example could be sought for high traffic areas in flooring and decking or for heavy engineering constructions. As a comparison, the Janka rating for Radiata Pine framing is 3.3, Mountain Ash and Alpine Ash are both 4.9 and Grey Box is 15 making it one of the hardest timbers in Australia.

Bowens has recently sourced some stock of 135×19 Grey Box decking. It ticks a lot of boxes with properties like excellent durability (class 1) and a very high Janka rating, as well as being visually appealing. This hardwood is from Southern Queensland and the Central and North Coast of New South Wales. The decking features earthy brown tones and the grain is often interlocked with a relatively fine and even texture.

Choosing the Wrong Timber

Not choosing the right timber can have terrible results, particularly if the whole job eventually needs replacement timber. There have been cases of decks where the surrounding concrete paver’s or rendered walls have been stained by tannin leaching.

This is caused by excessive tannins contained in the timber being released when wet. Unless a low tannin timber is selected in these situations, then designing a deck so that any leaching does not affect the area close by may be required. Also, further preparation like using a deck clean product and applying an all-over pre-coat of oil, prior to installation, will help minimise the leaching from the timber.

There is a lot of information available on specific timber properties covering many species of timber. Testing has been conducted to determine these properties which makes our selection informed and appropriate.

The Wood Solutions website and publications like Keith R. Bootle – ‘Woods in Australia’ are great sources of information on timber properties. Designers and builders need to consider timber properties to ensure efficient use and the long-term performance of their projects. 

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