Posted: 29 March 2018
The warning and amendment are part of MBIE’s response to the investigation into the performance of Statistics House in the 14 November 2016 Hurunui/Kaikōura earthquakes and recommendations from the Canterbury Earthquakes Royal Commission.
Loop bar warning
In 2016, MBIE commissioned an independent expert inquiry into Statistics House’s earthquake performance to determine the implications for New Zealand’s building regulatory system. The inquiry found the performance of the loop bar detail contributed to one of the four factors that led to the floor collapses in the building.
Public consultation on a proposal to ban the use of loop bar details in flange-hung double-tee precast concrete flooring took place from 27 September to 20 November 2017. After analysing consultation submissions, MBIE decided the most appropriate regulatory measure to prevent the use of non-compliant loop bar details was to issue a warning under section 26 of the Building Act.
A warning is appropriate for the following reasons:
- the loop bar detail is rarely used and a warning is proportionate to the level of risk
- a warning is consistent with New Zealand’s performance-based Building Code system
In addition to the warning, the amendments to B1/VM1 will also improve the resilience of precast concrete floors in new buildings.
The warning comes into force on 3 April 2018. From this date building consent authorities (BCAs) and territorial authorities must take the warning into consideration when deciding whether a new consent application complies with the Building Code.
The warning only applies to building consent applications and does not mean that existing buildings with loop bar details are unsafe. The expected performance of loop bar details depends on a number of other building design and construction characteristics. If building owners are concerned that their building may have potential issues they should seek advice from a structural engineer or discuss their concerns with their BCA.
MBIE is currently working with industry experts to develop additional guidance to assist engineering practitioners in the seismic assessment of precast floor systems.
Verification Method B1/VM1 Amendment 16
Amendment 16 to B1/VM1 will also take effect on 3 April 2018. It includes:
- an updated reference to the New Zealand Concrete Structures Standard NZS 3101.1:2006 Amendment 3
- updated requirements to the citation of the New Zealand Steel Structures Standard NZS 3404.1:1997.
The amendments ensure that the latest performance requirements are provided as a means of compliance.
The latest version of the Concrete Structures Standard includes enhanced provisions for the design of precast floors, which, in combination with the warning on loop bar details, will make these types of floors safer.
Both B1/VM1 amendments 15 and 16 will be accepted as a means of compliance during the three-month transition period from 3 April to 30 June 2018. After the transition period, only amendment 16 will be accepted.
Please note an exception has been made regarding the use of cast iron anchors and couplers, which will continue to be compliant under B1/VM1 amendment 16 until 1 November 2018. This will allow for continuity of anchor/coupler supply by giving manufacturers extra time to stock up on alternative couplers and anchors.