Timberzoo stocks kiln-dried native hardwoods suitable for outside applications in construction. For elevated decks, both DC1 and DC2 timbers are suitable. In close-to-ground structures, DC1 timbers are to be preferred. See table below:
Durability Class 2 species - DC2
Durability Class 1 species - DC1
Forest Red Gum
Spotted Gum (preservative-treatment)
Sizes of DeckingDecking is commonly available as 65 x 19mm, 86 x 19mm and 135 x 19mm. Of these the most stable dimension is 65mm - and the rule of thumb is not to exceed 5:1 in the ratio of width to thickness as an open deck. As the wetting and rapid drying affects the upper surface - stability is essentially a measure of the cupping or deflection of the top surface over time. Thicker decks add stability - and the Wharfdeck size 135 x 32mm is a more stable option in wider boards than its 19mm equivalent. 40 x 32mm hardwoods commonly used as screening can also be an interesting decking option.It is worth noting that timber decking is the most exposed and testing installation of the material in the construction repertoire. It is therefore vital that the design, choice of materials, set-out, fixing and protection of the timber be considered as more important than it is in other applications. There are many sources of advice and guidelines for building a timber deck - and I will refer you to several that are useful. Wood Solutionsprovides sensible, technical mainstream expert advice on their website - and our own Timberzoo advice sheet which will give you frank and fearless instruction in the do’s and don’ts of timber decks. A contributor worthy of a read is Ralph Bailey (Guymer Bailey Architects) who producedthis outline for Timber Queensland. Bear in mind that the green hardwood decks referred to in Queensland are more successful in high humiditynorth coast areas than they are in Victoria and South Australia with our dry hot summers. Kiln-dried timbers at about 15%MC are the preferred option in southern states.Common Issues - Tannins and Metal FilingsDon’t use a grinding disc near a timber deck - or sweep thoroughly afterwards if you do. The first dew or rain will cause carbon stains and black flecks to appear on timber surface as the metal fines run to carbon.All timbers leach tannins during rain. Some species - like Merbau - have very dark tannin runs. Other species have brown to milky brown tannins - but tannin leaching is common to all timber species. Yes - recycled timbers leach tannins. Darwin Stringybark is considered non-leachingin the industry - but it is likely the tannins are light-toned and do not stain - rather than non-existent. Seasoned timbers exude less tannins than green timbers, and oiling of timber and sealing of end-grain will reduce tannin leaching - but nothing will prevent it. Over time, as the fresh timbercase mellows to grey or silver, it will become more tannin-stable.All timber species will leach tannins into swimming pools and on to galvanised metal balustrading, sandstone walls and copings if the rainwater from your decking runs on to these materials. Washing with a pressure washer regularly will get rid of most of the staining - but it is practically impossible to eliminate or prevent.