Building products and systems used in building work need to comply with the National Construction Code and related Australian Standards.
The Queensland Building and Construction Commission (QBCC) has recently detected issues with the threaded rod, a material commonly used in the residential sector for providing tie-down to roof and wall frames particularly in high wind and cyclonic wind speed regions.
AS1684 Timber Framing Code includes a requirement that all metal straps, framing anchors and similar structural connections have a minimum corrosion protection of Z275, or in layman’s terms, 275 grams weight of zinc coating per square metre of surface area.
The QBCC’s research has confirmed that larger hardware chains do not commonly stock threaded rod with the required level of corrosion protection in single lengths commonly utilised by the average home builder (such as, 2.7metre or 3metre lengths). In lieu of a compliant product, the majority of hardware retailers are stocking threaded rod products with very lightweight zinc plating overcoated with an organic layer, which is claimed to mitigate the effects of corrosive environments.
The QBCC has requested evidence from resellers and importers of these alternate products regarding their suitability, in terms of corrosion resistance, of their organic-coated threaded rod products.
The QBCC is yet to receive satisfactory documentation demonstrating compliance with or equivalent performance, in terms of the corrosion resistance levels stipulated in AS1684.
The continued use and marketing of these coated products as “cyclone rods” or as being suitable for use in any residential timber-framed construction is misleading to consumers and building contractors alike.
Building contractors need to be acutely aware of their obligations, both to their home owner clients and to the QBCC, to ensure the materials and products being built into any residential construction complies with all relevant statutory requirements, including Australian Standards and the National Construction Code.
The QBCC’s message to industry practitioners is to demand of your hardware suppliers that they stock AS1684-compliant threaded rod so that your building work is compliant and will perform as expected for the life of the building.
It should also be remembered that the AS1684-compliant rod is only suitable for normal or benign environments.
If you are performing building works in corrosive environments, such as coastal or marine areas, you will need to consider upgrading the corrosion-resistance level of any threaded tie-down rods and related framing connectors and fixings to a heavier galvanised coating or a stainless steel-type product.
For more information call the QBCC (24/7) on 139 333 or visit www.qbcc.qld.gov.au