What Does a %NBS Rating Mean?
A Practical Guide for Building Owners, Landlords and Investors
What Does %NBS Mean for Building Owners?
One of the most common questions building owners ask is:
"My building is 34% NBS. Is that bad?"
The short answer is:
Not necessarily.
A %NBS (Percentage of New Building Standard) rating provides an indication of a building's assessed seismic performance relative to the requirements that would apply to an equivalent new building under current engineering standards, based on the assumptions, information and assessment methodology available at the time of assessment.
It is useful information, but it is not the whole story.
Think of a %NBS rating as the start of a conversation rather than the final answer.
What a %NBS Rating Does Tell You
A seismic assessment can help identify:
Structural vulnerabilities
Potential life-safety vulnerabilities
Relative seismic performance
Whether further investigation may be worthwhile
Whether strengthening options should be considered
A %NBS rating provides a useful starting point for understanding the assessed seismic performance of a building.
What a %NBS Rating Doesn't Tell You
A %NBS rating does not tell you:
❌ How much strengthening will cost
❌ Whether major strengthening is required
❌ Whether the building should be demolished
❌ Whether the building represents a good or poor investment
❌ How the building will perform in a specific future earthquake
❌ Whether additional investigation could change the assessment outcome
These questions require a broader understanding of the building, its condition, its vulnerabilities and its intended future use.
Why Similar Buildings Can Have Very Different Risks
Two buildings may both be assessed at 34% NBS yet have very different vulnerabilities and upgrade pathways.
For example:
One building may have a single weakness that can be addressed relatively easily.
Another may have multiple vulnerabilities requiring a more substantial upgrade programme.
Different assessments may also be based on different assumptions, available information, levels of investigation and assessment methodologies.
Understanding why a building received its rating is often more valuable than the rating itself.
Why %NBS Doesn't Equal Strengthening Cost
A common misconception is:
Low %NBS = High Cost
In reality, strengthening costs depend on many factors, including:
Structural system
Building layout
Existing condition
Accessibility
Heritage considerations
Future use
The specific vulnerabilities identified
In some cases, targeted interventions can significantly improve resilience without requiring extensive redevelopment.
A lower %NBS rating does not automatically mean an expensive strengthening project, although buildings with significant vulnerabilities may still require substantial intervention.
Why Investors Should Look Beyond %NBS
A seismic rating is only one factor in a property's overall value and performance.
Other important considerations include:
Building condition
Location
Deferred maintenance
Tenant requirements
Redevelopment potential
Lease arrangements
Long-term asset strategy
A lower rating does not automatically make a building a poor investment, just as a higher rating does not automatically make it a good investment.
The key is understanding both the opportunities and constraints before making significant investment decisions, rather than relying on a single percentage figure.
What Should Owners Focus On Instead?
Rather than asking:
"What is my %NBS rating?"
consider asking:
"What are the actual vulnerabilities in my building?"
and:
"What options are available to me?"
Good decisions are based on understanding:
The building
The risks
The available options
The likely costs and benefits of each option
The percentage itself is only one part of the picture.
When Is a Detailed Assessment Worthwhile?
A Detailed Seismic Assessment (DSA) can provide significantly more information than a screening-level assessment.
A DSA may help identify:
Critical structural vulnerabilities
Areas of reserve strength
Practical strengthening opportunities
A more complete understanding of building behaviour
In some situations a DSA confirms earlier assessment findings. In others it may identify either greater vulnerability or greater reserve capacity than previously recognised as a result of improved information, investigation or analysis.
For many owners, a detailed understanding of the building is far more valuable than relying on a percentage alone.
Questions Every Owner Should Ask
Before making decisions about strengthening, redevelopment or sale, consider:
1. What information already exists?
Gather:
Previous seismic assessments
Structural drawings
Building consent records
Engineering reports
Any previous strengthening documentation
2. What specific vulnerabilities are driving the assessment outcome?
Understanding the underlying issues is critical.
3. What options are available?
There is often more than one practical pathway forward.
4. What are my long-term plans for the building?
Different objectives often lead to different solutions.
Common Misconception
"My building is below 34% NBS, so I already know what needs to be done."
Not necessarily.
A percentage rating identifies an assessment outcome, but it does not automatically define the most appropriate solution or investment decision. owners should understand the vulnerabilities identified, the quality of the available information, and whether further investigation could provide a clearer picture of the available options.
Key Takeaways
✅ A %NBS rating is a useful tool, not a complete answer.
✅ Two buildings with the same rating can have very different risks and upgrade pathways.
✅ Understanding why a building received its rating is often more important than the percentage itself.
✅ A lower rating does not automatically mean expensive strengthening.
✅ Good decisions start with good information.
Need Advice on an Existing Building?
Whether you're reviewing a seismic assessment, considering a Detailed Seismic Assessment, purchasing a property or trying to understand what a %NBS rating means for your building, Essen Engineering can help you understand your options and make informed decisions.
Discuss Your Building With Us
Building Owner Guidance Series
Part 1: Understanding Changes to New Zealand's Earthquake-Prone Building System
Part 2: What Does a %NBS Rating Really Mean?
Coming Soon: When Is a Seismic Assessment Worthwhile?
Legislative Status Notice
Last Updated: 24 September 2026
This article provides general information only and should not be relied upon as building-specific engineering or legal advice. Building owners should seek professional advice specific to their property before making decisions regarding compliance, strengthening, redevelopment or investment.
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