New Zealand Seismic Standards — A Plain-English Overview

New Zealand seismic standards cover a lot of ground — building structure, non-structural services, seismic zones, and cross-Tasman equivalents for Australian sites. If you're new to the topic, the terminology alone can be a barrier. Here's a plain-English map of the main standards and ratings, and how they relate to each other.

%NBS — the structural starting point

%NBS (percentage of New Building Standard) is the most commonly quoted figure in New Zealand seismic assessments. It expresses how a building's structure is expected to perform relative to the standard required for a new building on the same site today. A building rated below 34%NBS is generally classed as earthquake-prone under the Building Act; 67%NBS or above is considered to meet current expectations for structural performance.

%NBS is a structural rating. It says nothing about what happens to services running through the building — gas lines, ceilings, ductwork — when the structure moves.

NZS 4219 — restraint of building services

A building can meet its %NBS target and still have gas pipework, HVAC plant, or ceiling systems fail in an earthquake, because those elements aren't braced to move with the structure. NZS 4219 is the New Zealand standard covering seismic restraint of these non-structural building services. It sets out how pipework, ducting, and plant should be fixed and braced so they don't fail, fall, or fracture when the building shakes — even if the structure itself performs well.

Restraint reduces the chance of a gas line fracturing. It doesn't isolate the supply if one does.

Seismic zones — how much shaking to design for

New Zealand is divided into seismic zones reflecting the level of ground shaking a site is likely to experience, based on proximity to active faults and known hazard data. Zone factors feed directly into structural design requirements — a building in a high-hazard zone is designed to a higher shaking demand than one in a low-hazard zone. We cover this in more detail in what New Zealand's seismic zones mean for your building.

AS 1170.4 — the Australian equivalent

Australian sites work to a different standard: AS 1170.4, the structural design actions code covering earthquake loads. It plays a broadly similar role to New Zealand's zone-based approach — translating regional seismic hazard into design requirements — though the two frameworks aren't directly interchangeable. For a closer look at how this applies to gas safety on Australian sites, see earthquake gas shutoff in Australia.

Where these standards leave a gap

Structural rating, service restraint, and zone-based design all reduce the chance that an earthquake damages a building or its services. None of them isolate gas automatically once shaking has occurred. A well-restrained pipe can still be compromised by ground movement beyond what any bracing anticipates — and once gas is flowing into a damaged building, the fire risk doesn't care how the structure was rated.

This is the gap automatic gas isolation fills. Commissioning a formal assessment of that risk is covered in our guide to seismic risk assessment in New Zealand.

Where the MK6 fits

The Solid State Seismic Shutoff — MK6 is an electronic trigger, not a mechanical valve. It detects the P-wave ahead of destructive shaking and isolates gas supply within 10 milliseconds — independent of %NBS rating, restraint standard, or seismic zone. It's a control that sits on top of structural and restraint compliance, not a replacement for it. NZ-made since 1971, with NZ-based support.

To talk through how these standards apply to your building or site, get in touch.