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The majority of saw mills produce rough sawn hardwood timber (green scantling). This material is mostly used for low value applications specifically, bearers and joists for building, battens, fence rails, timber palings and guide posts. There are also small niche markets for mills which supply customers with pallets, stakes, picket fences and small orders.
The sawn timber comes in a variety of sizes, the most common dimensions for the market being 7.5cm x 5cm (3x2in) and 10cm x 5cm (4x2). Prices improve the higher the Stress(F) Rating the sawn timber has.
The sawmill also produces a number of bi-products from the sawing process namely firewood, woodchips, 'fines' and sawdust.
Approximate prices as received by sawmills in the Southern Tablelands District for the product and former 'waste' material are listed below.
Sawn Material
Wood is highly variable in its appearance and strength properties. The main causes of variability are the anatomy of the wood; differences between mature and juvenile wood;sloping or other grain irregularities;basic density; reaction wood;knots and the presence of seasoning defect such as checks and cellular collapse.
These differences can lead to a number of concerns being raised by users of undried/unseasoned green timber. Common concerns in the utilisation of hardwood include;
These characteristics may be localised, within regions, or restricted to specific timber suppliers. They may be caused by the variability of the raw material, milling practices and/or handling. Some of these problems can be overcome by correct in-mill techniques (see Processing), while others are related to low standards of quality control. It is in this area which Australian hardwood suppliers will have to work the hardest to attain consistently higher timber values.
To assist timber consumers in ensuring that Australian hardwood timber meets technical and appearance specifications, both in domestic and increasingly in overseas markets, the hardwood industry has a set of agreed standards. These standards have been developed by Standards Australia (formerly Standards Association of Australia) an independent, not for profit association supported by all sectors of the Australian community- industry, unions, finance, government, academia and consumers. The standards are a point of reference for consumers to ensure they received what they paid for and know what uses their product is suitable for.
The standards currently most applicable to products within sawn, structural and engineering timbers include;
A large number of standards relating to flooring, weatherboards and fascia, mouldings, joinery, plywood, preservative treatments, building practice and testing methods are also available.
Standard AS 2082 is the most relevant standard to the existing hardwood timber industry in which almost all mills visually stress grade timber. Mills also determine the quality of sawn material that is to be used for appearance purposes (Appearance grading). Visually stress grading timber provides for the grading of sawn timber at the sawmill on the basis of defects present and ensures that different sawmills provide a product uniform in properties. Defects include the number and distribution of knots, the slope of grain, want, wane and sapwood, and the presence of gum pockets, gum veins, and hobnails.
Appearance grading of timber is based on the visual and physical characteristics of timber. the appearance grade is defined by the extent, size and nature of the imperfections and defects visible on the surfaces of the wood. Such imperfections may include;sloping or other cross grain, knots, knots and cone holes, resin and bark pockets, seasoning checks, seasoning checks in knots, kino veins and gum pockets, pith, bow spring, stains and wane and machining defects.
The building industry to which a large proportion of green scantling material goes, makes particular use of stress grading through the National Timber Framing Code. The Framing Code prescribes a strength for all timber used for structural purposes. This code uses the 'F Rating', a measure of the modulus of elasticity of timber. The F rating has a number of categories namely, F4, F5, F7, F8, F11,F14, F17, F22 and F27. The higher the grade the better the strength of the timber.
Much of Australia's softwood and hardwood timber is now mechanically stress-graded whereby a lateral force is applied to a piece of timber with the amount of timber deflection providing a strength rating (refer Australian Standards 1748 and 1749-1978). Australian hardwoods range in F rating from F4 to F27 while softwoods are commonly in the range of F5-F8 with some mills now cutting lengths to F11.
URL: http://online.anu.edu.au/Forestry/wood/hwd/raw.html