If you work in construction in New Zealand, whether you’re a builder, estimator, quantity surveyor, or project manager, NZS 3604 is one of those standards you live by without always thinking about it. It’s the rulebook behind almost every timber-framed home built in this country. And right now, it’s getting its most significant update in 15 years.
Standards New Zealand opened public consultation on the draft revision (DZ NZS 3604) in mid-2026, with submissions closing on 8 September 2026. The final published standard is expected in late 2026 or early 2027. Once it lands, it will change how residential buildings are designed, costed, and built across New Zealand.
This article walks through what NZS 3604 is, what’s changing, why it matters, and what the practical implications are for everyone in the construction industry.
What Is NZS 3604?
NZS 3604 is the NZ Standard for Timber-Framed Buildings. It sets out prescriptive design and construction requirements for light timber-frame residential construction, covering most homes and low-rise buildings.
What makes it powerful is its prescriptive nature. A builder or designer can follow NZS 3604 without needing a structural engineer to sign off every decision. It provides the tables, dimensions, grades, and details that let compliant construction proceed without Specific Design for standard situations.
The current version, NZS 3604:2011, has been the industry standard for 15 years. In that time, the housing market has shifted, building science has advanced, and other standards it references have been updated. The revision brings the standard in line with modern realities.
Why Is This Revision Happening Now?
A few converging pressures triggered this update:
- Medium-density housing demand. New Zealand’s housing shortage and urban intensification policies have increased demand for three-storey attached and detached dwellings. The existing standard didn’t fully cover full three-storey timber construction.
- Higher thermal performance requirements. The H1 energy efficiency schedule changes introduced higher insulation requirements, and the standard needed to provide practical construction details to support them.
- Post-Canterbury earthquake learnings. Research into how buildings perform on challenging ground, including liquefaction-prone and expansive soils, needed to be incorporated into prescriptive guidance.
- Related standards have moved. The Wind Loading Standard (AS/NZS 1170.2) was updated in 2021. The Timber Design Standard (AS NZS 1720.1) was updated in 2022. NZS 3604 needed to align with both.
- Market rationalisation. Some timber sizes referenced in the 2011 standard are no longer commonly available in New Zealand. The revision cleans this up.
The Seven Key Changes to NZS 3604
1. Three-Storey Timber Buildings Are Now Fully Covered
This is the headline change. The revised standard extends its scope to include full three-storey timber-framed buildings, lifting the maximum building height from 10 metres to 11 metres.
Previously, NZS 3604 only covered buildings with a partial third storey contained within the roof space, such as an attic conversion or dormer. A full third storey with its own floor and ceiling fell outside the standard’s prescriptive solutions, pushing designers into Specific Design territory.
The revision changes that. New provisions cover foundations, bracing, and structural framing for these taller buildings. However, three-storey buildings where the uppermost storey sits above a standard roofline will still require Specific Design for bracing. For foundations, those buildings are limited to reinforced concrete slab-on-grade.
What this means in practice: more projects, particularly terraced housing and medium-density developments, can now be designed using prescriptive solutions, reducing design cost and time for straightforward three-storey builds.
2. A New ‘Extra High’ Wind Zone
The revised standard introduces a new wind zone category: Extra High, with a maximum ultimate limit state wind speed of 55 m/s. The previous top category was Very High at 50 m/s. Anything above 55 m/s now requires Specific Design.
The exposure zone maps in Section 4 and the wind region and lee zone maps in Section 5 have both been updated to align with the 2021 Wind Loading Standard. This matters for buildings in exposed coastal locations and elevated sites where wind loads drive structural decisions.
On the bracing side, the revision simplifies wind bracing calculations. Previous tables existed for every wind zone separately. These have been consolidated into a single table for the High wind zone, with adjustment factors for other zones.
3. Updated Seismic Hazard Maps and Bracing Requirements
The earthquake zone maps in Section 5 have been revised to reflect NZ’s updated seismic hazard profile. New soil classifications for earthquake bracing demand have also been incorporated, which means the ground type formally influences seismic bracing requirements.
Research underpinning this change suggests that minimum seismic bracing provisions in the current standard may need to increase by up to 50% to meet deflection requirements under the seismic loading standard NZS 1170.5. This is particularly relevant for modern homes with open-plan layouts, large glazing areas, and complex floor plans, all features that reduce bracing wall availability.
The revision also creates a new dedicated bracing section (NZS 3604.2) covering subfloor bracing, wall bracing, isolated masonry walls, and steel bracing elements in wide openings.
4. Foundation Solutions for Challenging Ground
One of the most practically significant changes is the expansion of NZS 3604 to cover foundation solutions on moderately liquefiable ground and moderately expansive soils. This includes TC2-equivalent land in Christchurch, or clay-heavy sites that swell and shrink seasonally.
Previously, these sites required Specific Design: a geotechnical engineer and a structural engineer working through a custom solution for each project. The revision provides prescriptive foundation solutions for these conditions, though it still requires additional site assessment and geotechnical input to confirm which category a site falls into.
Updated construction details for suspended ground floors on these ground types have also been included, drawing directly on lessons from the Canterbury earthquakes.
5. Thermal Performance and Insulation Detailing
The H1 changes introduced in recent years significantly raised minimum insulation requirements. NZS 3604 needed to catch up with practical construction details that actually deliver those performance levels. The revised standard introduces:
- New wall intersection details that allow insulation to run continuously through corners and wall junctions rather than being interrupted by framing. Thermal bridging through framing is one of the biggest gaps between theoretical and actual R-values.
- 45mm thick lintels above openings at mid-floor junctions, creating space to incorporate insulation at those transition points.
- Service cavity battens, additional framing that creates a dedicated space for pipes, cables, and services inside the insulation layer rather than penetrating it.
- Framing overhang provisions that let the wall framing extend past the slab edge, creating space for slab edge insulation to fit behind the bottom of the cladding. This solves a practical problem many builders have had trying to achieve continuous insulation at the slab perimeter.
6. New Provisions for Common Building Situations
Several building elements that regularly appear on residential projects have historically sat in a grey zone, not clearly within NZS 3604’s prescriptive solutions. The revision addresses this:
- Stairwell walls that extend through upper storeys now have dedicated member selection tables and construction details.
- Parapet walls, which are common on contemporary flat or low-slope roof designs, now have specific provisions. Previously, parapets often needed engineering input even on straightforward residential projects.
- Isolated single-storey internal masonry walls, including feature walls and fireplaces, now have their own provisions.
- Foundation details for concentrated loads from larger door and window lintels have been added, addressing a common situation as residential openings get wider.
7. Timber Size and Grade Rationalisation
The 2011 standard included references to 70mm framing, which is no longer commonly available from suppliers. The revision removes most of these references, aligning the standard with what can actually be bought from a timber merchant. More broadly, timber sizes and grades throughout the member selection tables have been reviewed to reflect current market availability.
For estimators and QS professionals, this matters directly. If you’re pricing from a previous project’s bill of quantities as a template, check whether the timber specifications still align with the new standard.
What the NZS 3604 Changes Mean for Estimators and Quantity Surveyors
Most of the conversation about NZS 3604 centres on designers and builders. But the changes have direct implications for anyone pricing or managing construction costs.
Structural framing costs will shift. If seismic bracing requirements increase by up to 50% for some buildings, the quantity of bracing material and labour goes up. On a medium-density development with multiple units, that compounds across the whole project. You need to know what ground type you’re building on, what wind zone you’re in, and whether the new bracing provisions apply before you can price accurately.
Thermal performance detailing adds cost. Service cavity battens, thicker lintels, and more complex wall junction details all add labour and material. These aren’t huge numbers on a single house, but across a development they’re meaningful, and they need to be in your preliminary estimate, not added as a variation later.
Foundation costs on difficult ground need re-evaluating. Now that NZS 3604 includes prescriptive solutions for TC2-type ground, projects on those sites may not need full Specific Engineering Design, but they will still need geotechnical input to confirm site classification. Budget for that assessment, and for the prescribed solutions, which typically call for reinforced concrete slab-on-grade.
Three-storey buildings will need engineering fees in some configurations. Budget for Specific Design fees on any three-storey project where the top storey isn’t contained within the roof space. That’s an additional design cost that flows through to preliminary estimates.
Material specifications will change. With 70mm framing removed and timber grades rationalised, any estimate or bill of quantities that references the old standard may need reviewing before you rely on it as a template.
What’s the Timeline for the NZS 3604 Revision?
Public consultation on DZ NZS 3604 closed on 8 September 2026. Standards New Zealand will now work through submissions before finalising and publishing the revised standard. The expected timeframe for the final document is late 2026 to early 2027.
Once published, there will typically be a transition period during which both the old and new standard are acceptable for compliance. The length of that transition hasn’t been confirmed but is likely to be at least 12 months. Projects currently in design may complete under NZS 3604:2011, while new projects starting after publication will be expected to use the revised standard.
Start reading the draft now if you haven’t already. The consultation document is publicly available through MBIE and Standards New Zealand.
Why This Matters for Your Career in Construction
Standards don’t change often. When they do, they change everything: specifications, details, pricing assumptions, and compliance obligations. The professionals who understand what’s changed before the standard is published are the ones who don’t get caught out when a project is priced under the wrong assumptions or a building consent is submitted with outdated details.
This is exactly the kind of knowledge that separates a competent estimator or quantity surveyor from a great one. Knowing the technical standard is not the job of the engineer alone. Everyone who prices, manages, or delivers construction projects needs enough understanding of NZS 3604 to know when it applies, what it requires, and when a project falls outside its prescriptive solutions.
The revision reinforces something we teach throughout the NZES programme: the building code and its associated standards are not background noise. They are the framework within which every decision about materials, structure, and cost is made. Understanding that framework is not optional for anyone who wants to work competently in this industry.
