Selection and use of the correct products for the building, particularly for structural elements such as bracing, tie downs, fixtures and connectors, is a complex area. It is much more involved than just looking at whether standard, galvanised or stainless steel coatings or fixtures should be used.
There are a large number of Australian Standards and NCC provisions that contain corrosion, compatibility and exposure and structural capacity requirements that affect the selection, design and construction requirements for a broad range of building elements.
Therefore, don’t just assume the same fittings, fixtures and coatings to metal and steel products or bracing, roofing and flashings will be suitable for all buildings and locations. Close attention is required to ensure the correct detailing of building elements are chosen and used in the situations they are prescribed for.
Adam Dawson, Technical Manager at Pryda ANZ, says that steel strap cross bracing is a common form of bracing material, but questions how building professionals can tell if the products they’re using are the correct ones for use as a structural brace or tie down that complies with relevant Australian Standards.
‘Too often we are seeing structural tie down and bracing products substituted for thinner and/or lower grade hoop iron without proper consideration of the impact this has on capacity, performance and compliance,’ he says.
AS1684, the timber framing standard, requires the nominal size of the metal straps to be 30x0.8mm, with a minimum net sectional area of 15mm2 for 1.5kN/m bracing units and 21mm2 for 3kN/m units. The minimum grade of steel strap is to be G300.
‘The NCC at Part A5 specifies the product evidence requirements to demonstrate that the material/product will meet the requirements of the NCC,’ Adam explains. ‘One way to find out if a product meets these requirements is to get the product technical statement for the bracing. This will specify how and when it can be used and the performance requirements or relevant standards that is satisfies.
‘Therefore, to ensure your frame, and in turn your bracing, complies, you need to ensure you are across the NCC and Australian Standards requirements in selecting and using the correct bracing and tie down materials, and checking the product documentation to be confident that it complies.’
Another important aspect of checking your product technical sheets is to look for any limitations or scope of use of products because often they may contain specific conditions or restrictions on the use of the product.
With the NCC and standards constantly under review, you need to stay on top of the changes to ensure you are using the right materials. You don’t want to get caught out by any changing specifications.
With all of this in mind, the old adage of measure twice, cut once is a useful principle for selecting and using building products – check the requirements and documentation first before buying and applying.
This principle can save you many headaches and costs in the long run.