Skip to main content.

BC Update 180: Further update: Conformance of reinforcing steel mesh

Posted: 8 April 2016

BC Update
A third company has this week agreed to stop selling some steel mesh products amid concerns they might not comply with the Australia/New Zealand Standard (AS/NZ 4671:2001).

Steel and Tube announced this week that it was removing its product from the market until the mesh had been through a dual testing regime and had test results that demonstrate compliance with the standard.

As part of an investigation into seismic steel mesh, the Commerce Commission is testing samples of mesh from various companies. Results received by the Commission this week showed a sample of product tested from Steel & Tube did not meet the requirements of the standard. 

The Commission advised Steel & Tube of its concerns about the test results and requested further information. In response to that request Steel & Tube advised that it would be implementing a dual testing process on all of its SE seismic mesh. The Commission understands that until that testing is done and compliance is demonstrated, Steel & Tube will not sell that mesh. Further investigation is now underway.

Steel mesh is supplied to the residential market with the use limited to residential floor slabs, driveways and paths. It is also used in some commercial buildings.

Whatever the outcome of the Commerce Commission investigation, MBIE analysis has concluded that for houses there are no concerns about life safety and compliance with the Building Code.

MBIE is not yet clear about the extent to which the Steel and Tube product has been used in commercial or multi-story buildings.  However we’re checking this further and if it has been used in these buildings, case-by-case assessments would be needed.

Ductile steel reinforcing mesh is used to help control cracks in concrete floor slabs. It increases the slab’s flexibility, improving its performance in a serious earthquake. It’s one of a range of factors that contribute to a building’s resilience.

In 2011, following the Canterbury earthquakes, the ductility level for mesh in concrete slabs required by the Ministry’s Acceptable Solution and Verification Method was increased to a minimum elongation of ten percent. Before then, mesh in concrete slabs generally had an elongation of about two percent.

Homes built using this mesh will still be more resilient than the many of thousands of houses built prior to 2011.

While the compliance of the Steel and Tube product remains in doubt, MBIE advice is that this product should not be used in concrete slabs that haven’t yet been poured where the consent requires Grade 500E mesh.

This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: