Understanding ISA Assessments

New Zealand Environmental Technologies can provide a property owner with an accurate seismic assessment, as well as a detailed IEP report and an accurate %NBS rating. 

 

What is an ISA assessment?

An ISA (Initial Seismic Assessment) is completed by using the Initial Evaluation Procedure (IEP). 
It compares the existing building's percentage of structural earthquake strength relative to the New Building Standard (%NBS).

If your building is potentially earthquake-prone, you may be advised to conduct your own ISA (Initial Seismic Assessment).

 

What does "Earthquake Prone" mean?

A building is classified earthquake-prone if it has a seismic capacity of less than 34 %NBS (%New Building Standard).
This implies the building would suffer a high level of damage in a moderate earthquake.

Earthquake-prone buildings are likely to collapse which could cause injury or death.  

However, the %NBS rating is not enough. As a building owner need to know more: you need to understand how your building will behave in an earthquake – which is where you need NZET's expertise.

 

Seismic Assessment outcomes of risk per % can be seen in the table below.

 

Earthquake-Prone – %NBS rating less than 34%

Earthquake prone implies high level of damage is expected as a result of a moderate earthquake.
If you own an earthquake-prone building, you are required under the Building Act to carry out seismic strengthening work on it so that it is no longer an earthquake-prone building. The timeframe for carrying out such work depends on the location of your building on a seismic risk map as shown below.

New Zealand seismic risk map (source: MBIE)

 
 

There are priority and non-priority buildings. The timeframes for non-priority buildings are as follows:

  • 15 years in high seismic risk area.

  • 25 years in medium seismic risk area.

  • 35 years in low seismic risk area.


Priority buildings need to be remediated within half of the time available for non-priority buildings in high and medium seismic risk areas.

 

An Earthquake Risk – %NBS rating 34% - 66%

Although councils won’t insist such a building needs to be upgraded, such buildings are listed as “potentially an earthquake risk”. This means the damage in an earthquake can be high to minor, depending how close to the 34 %NBS rating the building is.

 

Unlikely to be an Earthquake Risk – %NBS rating at least 67%

Strengthening structural components can be investigated.

 

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Find out more information on ISA assessments or request a quote for your building today

 
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