Sub-standard punched strapping and tensioners alert by MiTek Australia
The most common application for punched strapping is in structural wall
bracing. AS1684 is the primary reference in the BCA that governs the use of metal straps
for wall bracing, and it is explicit regarding the minimum specifications required of the
strap to achieve design load capacity;
Typical size: 30mm x 0.8mm.
Minimum nett section: 15mm² (Type A - 1.5kN/m bracing capacity), or 21mm²
(Type B - 3.0kN/m bracing capacity).
Minimum steel grade: G300.
Minimum corrosion protection: Z275.
It has come to the attention of the industry that not all punched strapping available in
the market meets this standard. Some products are made from lower grade steel or with poor
galvanizing quality; while others do not specify nor satisfy the minimum nett section area
requirements after the holes are punched. Consumers are left to guess not only whether
they are suitable for Type A or Type B applications but are also expected to assume
suitability for use without any accompanying product specifications or certification that
satisfies AS1684 requirements.
Although tensioners are not clearly defined in AS1684, their use must obviously not reduce
the strength and stiffness of the metal straps that they are attached to. Their design should
be verified by laboratory testing to be assured of adequate performance. Sharp corners or flexible
shapes can prematurely snap or relax the straps before full design loads are reached.
Houses that are built with these sub-standard products risk excessive movement that can cause
plaster cracking and potential failure before the full design bracing capacity is reached.
Consumers are warned against using generic punched strapping and tensioners unless the supplier
is able to provide warranted product specifications that meet the requirements of AS1684. Buyers
are advised to source engineered building products only from reputable manufacturers and avoid
generic products that look similar but are not supported by any evidence of compliance.
MiTek supplies a range of engineered building products, including Structural Bracing Straps and
Tensioners that meet the full requirements of AS1684. Their performance has also been verified by
laboratory testing. These products are supported by a comprehensive product data sheet containing
manufacturing specifications, load capacities, recommended applications and installation instructions.
In addition, they are also accompanied by product certifications that warrant their full compliance
with AS1684 and the BCA.
For further information contact:
MiTek Australia Ltd
Address: 46 Monash Drive, Dandenong South, Vic, 3175
Phone: 03 8795 8....
Fax: 03 9702 9....
Web: www.mitek.com.au
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