NZS 3604: What Homeowners Need to Know About Timber-Framed Buildings

By James Chong | Published 3 September 2026

NZS 3604:2011 Timber-framed buildings is one of the most important standards used in New Zealand residential construction. It provides prescriptive design and construction requirements for many conventional timber-framed houses, including framing, floors, roofs, foundations, bracing and connections.

A significant revision of NZS 3604 is currently being proposed. For architects, builders and homeowners, understanding the difference between NZS 3604 design and specific engineering design is increasingly important.

Timber Frame Building Construction in New Zealand

What is NZS 3604?

NZS 3604 provides a practical, prescriptive method for designing and constructing many low-rise timber-framed buildings.

It covers matters such as:

• Timber floor framing

• Wall and roof framing

• Studs, joists, rafters and lintels

• Timber piles and foundations

• Bracing

• Fixings and connections

• Timber grades and member sizes

  
  

NZS 3604 is referenced by Acceptable Solution B1/AS1 as one recognized pathway for demonstrating compliance with Building Code Clause B1 – Structure.

Importantly, NZS 3604 is not the Building Code itself. It is a technical standard that provides prescribed solutions within defined limits.

Does using NZS 3604 mean you do not need a structural engineer?

Not necessarily.

A conventional residential building construction or alteration that is fully within the scope and limitations of NZS 3604 may be capable of being designed by an architect without a structural engineer designing all the structural element.

For example, a conventional house may be designed using NZS 3604 for:

• Timber framing

• Standard floor and roof structures

• Conventional bracing

• Standard timber pile foundations

• Prescribed lintels and beams

• Standard connections and fixings

  
  

However, the designer must establish that the project complies with the requirements and limitations of the Standard.

The important question is:

"Does the proposed structural design fall within NZS 3604?"

When is a structural engineer required?

Structural engineering or other specific design may be needed when the proposed construction falls outside the prescriptive solutions of NZS 3604.

Typical examples include:

• Large or unusual structural openings

• Long-span beams

• Significant cantilevers

• Complex roof structures

• Unusual structural connections

• Retaining walls

• Challenging or poor ground conditions

• Significant alterations to existing structures

• Structures outside the scope of NZS 3604

• Certain multi-storey or complex buildings

  
  

For example, removing a wall in an existing house may appear straightforward, but the wall could be supporting roof or floor loads or providing an important part of the building's bracing system.

Similarly, a large opening for bi-fold or sliding doors may require structural design beyond the standard NZS 3604 tables.

The architect's role

An architect produces architectural design that considers the structural strategy from the beginning.

An architect can assess:

• Whether the proposed building is suitable for NZS 3604

• Building geometry and structural spans

• Bracing requirements and distribution

• Foundation requirements

• Roof and floor framing

• Structural wall locations

• Large openings and beams

• Whether specific engineering is likely to be required

  
  

Where the project remains within NZS 3604, the architect can undertake and document the relevant structural design. For example, for the removal of a bracing wall of a house, an architect can calculate the bracing and earthquake demand of a house and lodge the building consent without the need for a structural engineer’s design.

Where specialist engineering is required, the architect can coordinate the structural engineer's design with the architectural drawings and ensure that the structural solution works with the overall building.

The proposed new NZS 3604

A major revision of NZS 3604 is currently being proposed in 2026.

The draft revision is intended to bring the Standard up to date with changes in construction practice, timber products, structural research and Building Code requirements.

Some of the proposed changes include:

Three-storey timber buildings

The draft proposes expanding NZS 3604 to accommodate a wider range of three-storey timber-framed buildings and increasing the maximum building height from approximately 10 m to 11 m.

However, some three-storey configurations may still require Specific Design, particularly for bracing.

Challenging ground conditions

The proposed revision introduces additional provisions for certain sites affected by conditions such as:

• Liquefaction

• Moderately expansive soils

• Other ground conditions previously outside the simplest NZS 3604 foundation pathway

  
  

This could allow more conventional residential buildings to use prescribed foundation solutions, although geotechnical assessment may still be necessary depending on the site.

Updated timber and structural provisions

The draft also proposes updates relating to:

• Timber sizes and grades

• Wind loading

• Earthquake considerations

• Large openings and concentrated loads

• Stair and upper-level framing

• Thermal performance

• Current timber design standards

  
  

These changes are intended to better reflect modern residential construction.

NZS 3604:2011 vs the proposed revision

Area	NZS 3604:2011	Proposed revision
Conventional timber houses	✓	✓
Two-storey construction	✓	✓
Three-storey construction	Limited	Expanded provisions proposed
Building height	10 m	11 m proposed
Challenging ground	Limited	Expanded provisions proposed
Large openings	Prescribed solutions within limits	Additional provisions proposed
Timber products	Existing product assumptions	Updated
Wind/structural provisions	Existing requirements	Updated
Thermal provisions	More limited	Expanded
Specific Design terminology	SED commonly used	"Specific Design" proposed

The proposed revision is not yet the new standard. It is currently in the consultation stage and may change before final publication. It should not currently be relied upon for construction or building consent design unless and until it becomes an applicable compliance document.

Why early structural coordination matters

Structural decisions made during the early design stages can significantly affect the cost and practicality of a project.

For example, changing the location of a wall, reducing a beam span , or adjusting a large opening may allow a design to remain within a simpler NZS 3604 solution.

Conversely, leaving structural decisions until the end of the design process can result in:

• Larger beams

• Additional posts

• More complicated foundations

• Additional engineering fees

• Architectural redesign

• Construction complications

  
  

The most efficient approach is often to use NZS 3604 wherever practical and appropriate, while using specific structural design where it is genuinely required.

The role of architect and structural engineer

The two roles are complementary.

An architect can:

• Develop the architectural design

• Assess whether NZS 3604 is applicable

• Coordinate structural requirements

• Undertake NZS 3604-based design where within their competence

• Prepare and coordinate building consent documentation

• Engage and coordinate structural engineers where required

  
  

A structural engineer can:

• Undertake specific structural design

• Design structures outside NZS 3604

• Analyze complex structural systems

• Design unusual beams, connections and foundations

• Address structural conditions requiring specialist engineering expertise

Drafting of Architectural Plan

Final thoughts

NZS 3604 remains a fundamental part of New Zealand residential construction. It provides an efficient and practical pathway for many conventional timber-framed buildings. The proposed revision is significant and may expand the range of buildings and site conditions that can be addressed through prescriptive timber design.

However, NZS 3604 does not eliminate the need for professional judgement or structural engineering. The appropriate approach is to identify which parts of a project can be designed using the Standard and which require specific design.

At Unveil Architects, we offer initial free, no-obligation checks for alterations and remodeling works in Auckland and liaise with appropriate engineers for design from the early stages to optimize cost-effective architectural design and solutions for clients.

Contact James (email: james@unveilarchitects.com; mobile: +64 22 6571063) for a free, no-obligation quote for your next project.

Disclaimer: The views expressed in this post are my own and do not represent the opinions of any organization or employer. The content is for general information only and should not be taken as professional advice.