Wood species & their properties

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Question: What levels of tannin does jarrah contain?

Answer: Jarrah is less prone to tannin staining than merbau but can still produce quite a lot of tannin. We therefore suggest scrubbing with deck cleaner before installation, as recommended by the manufacturers, to remove excess tannin. This is only necessary (a) if the timber is exposed to rain, and (b) if the tannin is likely to wash off onto a sensitive surface such as sandstone pavers or light coloured render. If the deck is protected from the weather no tannin will leach. If it is open to the weather but there are no absorbent surfaces nearby you can let nature take its course and the tannin will eventually wash out.


Question: Is jarrah or dark red meranti a better material for windows?

Answer: According to Australian Standard 5604, Timber - Natural durability ratings, jarrah is rated Class 2 for above-ground uses, whereas dark red meranti is Class 3 on a scale of 1 to 4, where Class 1 is the highest durability. Jarrah is therefore considered the more durable timber. Nevertheless, we consider dark red meranti is suitable for window joinery unless the building is particularly severely exposed. We assume, or course, that both timbers would be kiln-dried and of suitable quality for window joinery. You would also need to be sure that the dark red meranti falls into the accepted density range and is not simply a dark colour.


Question: We are looking at importing outdoor furniture in red meranti timber. Is it suitable for outdoor use in Australia?

Answer: The trade name "meranti" groups together a number of very similar species. For convenience the meranti species are divided into light red and dark red meranti. We consider light red meranti is not suitable for permanent exposure to the weather, but dark red meranti would be suitable providing it is coated with outdoor furniture oil or a similar water repellent product. As the name suggests, the dark red meranti species are a deeper reddish-brown, and are more durable outdoors. They are also denser than the light red group, ranging from 640-720 kg/m³.


Question: Is the timber from Leopard and Liquid Amber trees suitable for wood turning?

Answer: Leopard wood (Caesalpinia ferrea) is hard and heavy, hence its other name "ironwood". It will need care in drying to avoid checks and splits. However, it should turn satisfactorily as long as these problems can be avoided. Liquidambar is a much lighter wood and also can be turned satisfactorily, with the usual care.


Question: Can you advise as to whether unpainted, untreated hoop pine exposed in a marine environment (i.e. regularly doused with salt water) would exhibit rot resistant qualities?

Answer: Hoop pine is not a durable timber, and we would not recommend it in exposed situations, marine or otherwise. It's a fine timber for protected uses but has little resistance to wood rot when untreated.


Question: AS 1684.4-2006 has timber sizes for unseasoned timber. What timbers am I buying at my local hardware store? Seasoned or unseasoned. Are unseasoned timbers more prone to twisting particularly treated pine?

Answer: Most pine products are seasoned (kiln dried). However, in the case of treated pine, you may be offered seasoned or unseasoned material. Unseasoned treated pine will shrink slightly as it dries out. Also it is more inclined to twist and develop surface cracks called "checks". For this reason treated pine decking and similar products are always kiln dried. However it is impractical to kiln dry some of the larger sizes of treated pine, particularly large diameter rounds, and these are likely to be sold unseasoned. If in doubt, your timber merchant should be able to advise. Similarly, structural sizes of hardwood may be sold seasoned or unseasoned, while products such as decking, flooring and mouldings are always kiln dried.


Question: What hardwood is suitable for a boat jetty in a salt water environment, it is over salt water not in it and could be treated away from the water before being fitted.

Answer: Wood generally tolerates a salt environment quite well - fresh water is actually more hazardous since it is more conducive to mould and fungal growth. If you were planning to put the timber into salt water it would be a different story - not because of the salt, but because of marine borers. However, above the water any Durability Class 1 hardwood would be satisfactory, for example tallowwood, turpentine, spotted gum, river red gum and so on. No special treatment is necessary, but make sure all fasteners are stainless steel.

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