With surging domestic and global demand for renewable timber products putting pressure on Australian supply chains, it is timely to reiterate how timber products supplied into the Australian construction market comply with Australian Standards and are fit for purpose when used in a manner consistent with AS1720.1 or AS1684.
Machine Graded Pine (MGP) timber products are well known and understood in the Australian market and consumers can have confidence about the veracity of the claims made on these products, if that timber is produced in sawmills that use a ‘qualified’ MGP grading method. Having a qualified grading method requires significant investment in grading equipment, in initial destructive testing of products to confirm structural properties, in ongoing verification of timber product properties, and in periodic evaluation of the grading method used.
Machine stress-grading uses a machine to bend, or otherwise measure the physical properties, of each piece of timber. The machine measures the stiffness of the piece and uses correlations to predict its modulus of elasticity and strength in order to sort into a stress grade. The targets for modulus of elasticity and strength are carefully selected to control the other structural properties of the sorted timber (tension, compression, and shear strength). Regular sampling and testing throughout a batch is used to verify that the sorted timber meets the stress grade applied.
Branding requirements for MGP timber under AS1684 include a grade stamp applied to the timber after the machine stress grading process. Once the machine has sorted a piece of timber based on its physical properties, a grade stamp is applied which will enable all subsequent people in the marketing and distribution supply chain to identify the structural properties applicable to that piece of timber. Some grading machines utilize markings that run the length of each graded piece of timber to identify certain characteristics along the length, which are analyzed by cameras or skilled visual graders to determine the final grade. Ultimately, it is the final printed grade mark that indicates the grade of the whole piece, such as a laser-printed mark at regular intervals.
Most Australasian timber processing operations are audited by a third-party wood products quality assurance body, such as Engineered Wood Products Association of Australasia (EWPAA). Detailed audits are undertaken routinely (e.g., six to twelve months) as a process of independent assurance that the MGP timber products do indeed comply with Australian Standards, and that appropriate quality management systems are in place. Further information about EWPAA’s certification activities can be found here.
Structural timber products sold in the Australian market (e.g., F-grades and MGP grades) must not be re-machined, ripped, or re-branded as either F grade or MGP (excluding normal construction practices), unless the product is re-graded by a responsible entity using a machine stress grading method meeting the requirements of AS/NZS 1748 series. If a product is docked, it cannot be upgraded from the lowest grade of the piece that it was docked from. Colour brands on MGP timber do not indicate a grade higher than the grade of the original docked length.
It should be noted that visual grading of timber is not an acceptable method to designate or re-designate timber as MGP. MGP grades can only be given to timber that has been machine graded in accordance with AS/NZS 1748. Re-branding of timber by other methods, or subsequent supply or use of MGP graded by a non-legitimate method, may be in breach of building material legislation in some States, and potentially carries significant penalties to the responsible entity that is undertaking those activities and making those claims.
How can fabricators be confident they are using
timber which meets the Australian Standards?
Fabricators do need to ask several questions of their suppliers to ensure they have done reasonable due diligence checks on the timber. If a supplier cannot get answers to these questions from the manufacturer, it throws up questions about whether the timber meets Australian Standards.
- Is the timber visually or machine graded? If visually graded, it is not F-graded timber can be either machine or visually graded, but the correct standard for visually graded F grades is AS2858, not AS/NZS1748.
- If F grades or MGP grades are sold as meeting AS/NZS1748, ask to see a copy of the report qualifying the grading method to AS/NZS1748.2. Only Australian producers using bending type grading machines are exempt from this requirement. Overseas producers are not.
- Ask for a copy of the most recent annual verification check on the grade. As this is a requirement of the standard, all legitimate producers will have this for one size/grade combination each year.
EXAMPLE OF A BRAND
It must contain
- Grade (MGP10)
- Standard (AS/NZS1748)
- Producer name or mill code (OneFortyOne)
- Moisture status (Seasoned or can be abbreviated to “S”)
It should include information to allow traceability back to a production run (in this example, date, time, and individual piece number allow this).
About EWPAA. Engineered Wood Products Association of Australasia (EWPAA) is a member association for manufacturers of a broad range of engineered and solid wood products located throughout Australasia, including Australia, New Zealand, Fiji, and Papua New Guinea. On behalf of our members, we coordinate a market development program which involves the following aspects: Product Certification and Testing, Standards Development, Education & Training, Research & Development, Market Maintenance, and Technical Promotion. See EWPAA website: ewp.asn.au