When Is a Seismic Assessment Worthwhile?
Updated: 2 days ago
Do I actually need a seismic assessment & when is a seismic assessment worthwhile?
It is a common question when buying, selling, leasing, altering or planning the future of an existing building.
The reality is that not every building requires a new assessment. In many cases, the better question is:
What information do I need to make a confident decision about this building?
When linked to a clear property, investment or asset-management objective, a seismic assessment can reduce uncertainty, identify structural vulnerabilities and help clarify the options available.
What Is a Seismic Assessment?
A seismic assessment considers the assessed seismic performance of an existing building under earthquake actions, based on the information available and the level of investigation undertaken.
Depending on its purpose and level of detail, the work may include:
Reviewing structural drawings and consent records
Inspecting the existing building
Identifying structural systems and load paths
Reviewing previous alterations or strengthening
Assessing potential structural vulnerabilities
Undertaking engineering calculations and analysis
Reporting the building’s assessed seismic performance
The appropriate scope depends on the building, the quality of the available information and the decision the owner needs to make.
When May a Seismic Assessment Add Value?
Buying a Building
Seismic information can form an important part of due diligence when purchasing an existing commercial property.
Better structural information may help owners understand matters that could influence:
Future capital expenditure
Insurance or lending discussions
Tenant requirements
Planned alterations
Redevelopment potential
Long-term asset value
Seismic performance should not be considered in isolation. Building condition, deferred maintenance, leases, location and future use may also influence the investment decision.
Selling a Building
Existing engineering information can provide prospective purchasers with a better understanding of the building and reduce uncertainty during due diligence.
Before commissioning a new assessment, consider whether existing reports, drawings and consent records already contain useful information.
Where uncertainty remains, a focused engineering review may help determine whether further investigation is worthwhile.
Lease Negotiations
Existing and prospective tenants may ask about:
The building’s seismic rating
Earthquake-prone building status
Previous strengthening work
Planned upgrades
Long-term occupancy considerations
Understanding the available information can support clearer and more informed discussions between owners and tenants.
Insurance or Lending Discussions
Insurers and lenders may request seismic information to help them understand a property and its associated risks.
Before commissioning additional work, clarify:
What information is being requested
Why the information is required
Whether an existing report is acceptable
Whether a particular level of assessment is expected
A broad request for an “NBS rating” may not accurately describe the information the other party needs.
Significant Building Alterations
Alterations may expose undocumented conditions or raise questions about how the existing structure works.
A seismic assessment or targeted structural review may be worthwhile before:
Removing walls or columns
Creating larger openings
Adding significant loads
Changing the internal layout
Undertaking a major refurbishment
Installing heavy equipment
Extending the building
Understanding the structure early can help reduce redesign, consent delays and unexpected construction work.
Proposed Change of Use
A proposed change in use may introduce different occupancy, loading, performance or regulatory considerations.
Examples could include converting:
A warehouse into offices
An industrial building into a community facility
A commercial building into residential accommodation
An agricultural building into a public venue
An existing facility into a higher-occupancy use
An early engineering review can help identify potential structural implications before significant design expenditure is committed.
Whether a proposal constitutes a formal change of use under building legislation should be confirmed with the relevant territorial authority.
Existing Earthquake-Prone Building Concerns
Where a building has an earthquake-prone building notice, a lower seismic rating or an older assessment, reviewing the available information may help determine:
What is already known
Which vulnerabilities govern the result
Whether important assumptions remain valid
Whether previous strengthening has been confirmed
Whether further investigation may change the understanding of the building
What practical options may be available
A lower rating does not, by itself, establish the level of risk, the work required or the most appropriate investment decision.
Long-Term Asset Planning
Structural information can support decisions about whether to:
Retain the building
Strengthen it
Refurbish it
Redevelop the site
Change its use
Sell the property
Plan staged capital works
An assessment provides the most value when its scope is tailored to the decision being considered.
Start With the Information You Already Have
Not every building requires a new seismic assessment.
In many cases, the most cost-effective first step is reviewing the information that already exists.
This may include:
Previous seismic assessments
Structural drawings
Architectural drawings
Building consent records
Producer statements
Construction monitoring records
Strengthening documentation
Geotechnical reports
Alteration and fit-out records
Property condition reports
Reviewing this information may answer immediate questions, reveal important gaps and help define an appropriate next step.
It can also avoid duplicating engineering work that has already been completed.
ISA, IEP or DSA?
The appropriate level of assessment should reflect the purpose of the work.
Screening-Level Assessments
Older buildings may have an Initial Evaluation Procedure, commonly referred to as an IEP, or a more recent Initial Seismic Assessment.
These assessments can be useful for:
Preliminary due diligence
Portfolio screening
Identifying buildings that may warrant further investigation
Supporting early asset-planning discussions
Because screening-level assessments may rely on limited information and broad assumptions, they may not provide sufficient detail to support strengthening design, detailed risk assessment or major investment decisions.
Detailed Seismic Assessment
A Detailed Seismic Assessment, or DSA, examines the building and its structural systems in greater depth.
Depending on the building and available information, a DSA may include:
Detailed review of existing records
Building inspections and investigations
Verification of structural details
Engineering calculations and analysis
Assessment of individual structural mechanisms
Identification of critical vulnerabilities
Consideration of areas of reserve capacity
In some cases, a DSA confirms earlier findings. In others, improved information, investigation or analysis may identify greater vulnerability or greater reserve capacity than previously recognised.
The purpose should be to improve understanding of the building and its vulnerabilities, not simply to generate another percentage.
Real-World Comparison: Screening Result Versus Detailed Understanding
A recent assessment of an operational building illustrates why further investigation can sometimes be worthwhile.
An earlier IEP recorded an estimated seismic rating of 71%NBS for the building. This provided a useful screening-level indication, but it did not explain in detail which structural elements governed the outcome or where the building had reserve capacity
A later DSA examined the structural system, individual wall lines, roof-to-wall connections, columns, load paths and foundation response in substantially greater detail.
The detailed work found that:
The reinforced masonry walls formed the primary lateral-load-resisting system.
The reviewed wall elements had significant capacity relative to the assessed demand.
The reviewed superstructure walls and several assessed structural elements demonstrated capacity exceeding the assessed demand on the reviewed basis, while the overall interpretation remained dependent on confirmation of foundation restraint mechanisms.
The key remaining issue was not a general lack of wall strength, but confidence in the continuity and reliability of the wall-to-foundation load path and the available foundation restraint mechanisms.
Importantly, the DSA did not simply replace 71%NBS with an unconditional whole-building rating above 100%NBS. The final whole-building interpretation remained conditional on confirming how the actual foundation restraint mechanisms operated.
The most valuable outcome was not a revised percentage. It was a clearer understanding of the structural systems, vulnerabilities and priorities that should influence future decisions.
The value of the DSA was therefore not merely a revised percentage. It provided a clearer understanding of:
Which elements had substantial reserve capacity
Which interfaces required further attention
What controlled the whole-building assessment
Where any future investigation or engineering effort should be directed
This is a useful example of why a detailed assessment can add value. It can change the owner’s understanding of the building, even where it does not immediately produce a single unconditional whole-building rating.
A screening assessment can identify that further consideration may be appropriate. A detailed assessment can explain why, identify the governing mechanisms and clarify what should happen next.
When Might a Full Assessment Not Be the First Step?
A full seismic assessment may not be the best immediate response where:
The owner has not defined the decision to be made
Existing reports or drawings have not been reviewed
A targeted investigation could answer the immediate question
The building is likely to undergo major redevelopment
The issue relates to an isolated structural element
The assessment result would not affect the owner’s intended course of action
In these situations, a preliminary engineering review may be more proportionate.
That review can help determine whether the next step should be:
Reviewing existing information
Undertaking a site inspection
Completing a targeted investigation
Preparing an ISA
Undertaking a DSA
Developing strengthening options
Completing a broader feasibility study
Questions to Ask Before Commissioning an Assessment
1. What decision am I trying to make?
Is the assessment intended to support a purchase, sale, lease, alteration, redevelopment or long-term asset plan?
2. What information already exists?
Review previous assessments, drawings, consent records and strengthening documentation before starting again.
3. What uncertainties need to be resolved?
Identify whether the key concern is:
Overall seismic performance
A particular structural vulnerability
Previous alterations
Unverified strengthening
A proposed change
Future investment requirements
4. What level of assessment is appropriate?
The scope should be proportionate to the building, the available information and the importance of the decision.
5. Will better information change my decision?
An assessment provides the greatest value when its findings can influence planning, risk management or investment decisions.
Common Misconception
“If I commission a seismic assessment, I will automatically be required to strengthen the building.”
Not necessarily.
Commissioning an assessment provides information that may assist decision-making. It does not, by itself, automatically create a requirement to strengthen the building.
Any legal obligations will depend on matters including:
The applicable legislation
The building’s formal status
The work being proposed
Whether an alteration or change of use is involved
The requirements of the relevant territorial authority
The assessment findings may nevertheless influence future regulatory, operational, property or investment decisions.
The Right Question
Rather than asking:
“Do I need a seismic assessment?”
consider asking:
“What information do I need to make a confident decision about this building?”
That question helps ensure that any engineering work is focused, proportionate and connected to a clear purpose.
Key Takeaways
Not every building requires a new seismic assessment.
Review existing information before commissioning another report.
Screening and detailed assessments serve different purposes.
A DSA can identify which mechanisms govern a building’s assessed performance.
A seismic assessment does not automatically require strengthening.
The value of an assessment lies in improved understanding, not simply another percentage.
Good engineering information can support better property and investment decisions.
Need Advice on an Existing Building?
If you are purchasing a property, reviewing an earlier seismic assessment, planning alterations or considering a Detailed Seismic Assessment, Essen Engineering can help review the available information and identify a practical next step.
Discuss Your Building With Us
Building Owner Insights Series
Part 1: Understanding Changes to New Zealand’s Earthquake-Prone Building System
Part 2: What Does a %NBS Rating Really Mean?
Part 3: When Is a Seismic Assessment Worthwhile?
Coming Soon: My Building Has a Low %NBS Rating. What Are My Options?
Legislative and Professional Disclaimer
Last updated: 6 October 2026
This article provides general information only and does not constitute building-specific engineering, legal, financial, insurance or investment advice.
The appropriate assessment pathway depends on the building, available information, proposed work and owner objectives. Building owners should obtain advice specific to their property and confirm applicable statutory requirements with the relevant territorial authority before making decisions concerning compliance, strengthening, alteration, redevelopment or investment.
The real-world comparison is presented to illustrate the difference between screening-level and detailed assessment. It should not be interpreted as suggesting that all detailed assessments will result in a higher rating or identify reserve structural capacity.
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