Earthquake Prone Buildings

Essentially, engineering uses a scientific and mathematical approach to finding the most appropriate technical solution to your problem. In designing construction solutions, factors that Engineers often consider include: safety, strength, durability, legal liabilities and cost. The effect of external forces, both natural and man-made, also has a major bearing on engineering design.

When developing land, building or making significant alterations, there are a number of engineering disciplines that will be very important to the project. While some disciplines are quite specialised, there are often occasions where engineering disciplines impact or overlap each other.

Here are some of the engineering disciplines you may come across when looking at development and construction in New Zealand…

Using a simple profiling tool, local councils have a set timeframe to identify buildings as potentially earthquake prone (with a seismic capacity of less than 34% NBS). Once a building is identified as potentially earthquake prone, the building owner has 12 months to challenge or accept the assessment.

The council then makes the final decision and, if required, issues an earthquake prone building notice. On receipt of this notice building owners have a set timeframe, based on the seismic risk of the region and importance of the building being considered, to either strengthen or demolish the building.

Our View

Regardless of the new legislation, banks and insurers are increasingly asking for the seismic strength of commercial buildings before offering finance or insurance. Many request that buildings be strengthened to at least 67% NBS, whereas the earthquake prone regulations consider a minimum of 34% NBS. Furthermore, many building tenants will expect a seismic capacity of at least 67% NBS.

Our opinion is that while the new legislation will require the upgrade of buildings with a low seismic strength, it is likely that commercial pressure will be the key driver.

Here at EDC we know a lot about this stuff and we are happy to talk you through it. Contact us here.

The Ministry of Building Innovation and Employment (MBIE) have prepared some very good web based resources outlining some of the specifics of the new legislation. Full details of the new system for identifying and managing Earthquake Prone Buildings can be found here.

What is an earthquake prone building

An Earthquake Prone Building is a building that will have its ultimate structural capacity exceeded in earthquake shaking equivalent to one third (33.3%) of the current building code design level. Current building code design level is known as the “new building standard” (NBS), therefore, we say that any building (there are some exceptions – specifically houses) with a seismic capacity less than 34% NBS is earthquake prone.

What is happening?

Territorial Authorities, the local district and city councils, have been tasked with identifying potentially earthquake prone buildings in their jurisdiction, and notifying building owners.

Will my building be identified?

Councils will use two methods to identify potentially earthquake prone buildings.

Identify potentially earthquake prone buildings using simple profiling tools which take into account the buildings age, height and construction materials, all within a set timeframe. Specifics can be found here or contact EDC and we can help clarify if your building is likely to be identified as potentially earthquake prone. Identify any building as potentially earthquake prone at any time, or in other words, there are no restrictions or timeframes for this assessment. For example, the local council may request a seismic assessment be included in a Building Consent application for a building alteration. Building owners will be notified if their building is potentially earthquake prone.

When will this happen?

Councils have set timeframes to identify all potentially earthquake prone buildings in their jurisdiction using the profiling tool described above. Deadlines range from 1 January 2020 to 1 July 2032 depending on the seismic risk of the building location and whether the building is considered as priority. For more information, click here.

Priority buildings includes those with unreinforced masonry (URM) elements that could fall into the street or major thoroughfare. For information on priority buildings, see here.

I’ve been identified as potentially earthquake prone, what do I do?

Contact EDC. We’d be happy to provide advice specific to your situation.

Essentially you have two options.

Challenge the council identification by having your building assessed by a Chartered Professional structural engineer and submitting a report to the council demonstrating why the building is not earthquake prone. Accepting the council assessment and plan for future enhancement, or consider demolishing the building. Either way, any response to the council must be submitted within 12 months of receiving notification that the building is potentially earthquake prone.

There is no simple answer to this so please contact EDC and we can work through your specific situation.

Then what happens?

If an engineer can demonstrate to the council that a building is not earthquake prone, and the council agree, then the building will be removed from the list of potentially earthquake prone buildings.

If your engineer shows that the building is in fact earthquake prone, and you provide this report to the council, the building will be assessed as an earthquake prone building and will be assigned one of two categories:

• Seismic capacity less than 20% NBS or…
• Seismic capacity from 20% NBS but less than 34% NBS.

If you do not submit an engineer’s report to the council, you will be automatically categorised as less than 20% NBS.

Either way, an Earthquake Prone Building notice will be issued which must be affixed to the building in a prominent location, such as on the front door. The building will also be logged on the public register of earthquake-prone buildings.

Ultimately only the council can determine whether a building should be categorised as earthquake prone.

How does an engineer assess my building?

Engineers must follow specific guidelines for the seismic assessment of existing buildings and will produce either an Initial Seismic Assessment (ISA) or a more comprehensive Detailed Seismic Assessment (DSA). Some assessment of the foundations and underlying ground conditions may be required, and if so we can undertake a geotechnical investigation

Here at EDC we have considerable experience of applying the guidelines and assessing buildings. We would be happy to discuss your situation with you to determine the most suitable path to follow. We understand that economics is likely to be a major driving factor in determining what level of seismic assessment to undertake. A well-considered seismic assessment should be viewed as an investment that allows future decisions to be made with confidence. No two buildings and situations are alike, so speak to EDC. We’d be happy to provide advice specific to suit your needs.

What do I do with my earthquake prone building?

Owners of buildings designated as earth quake prone must take action within set time frames to apply the outcome of the decision.

All buildings issued with an earthquake prone notice must either:

• Be strengthened to at least 34% NBS so that the building is no longer earthquake prone or…
• Be demolished.

From the date an earthquake prone building notice is issued, the timeframe for completing this work varies from 7.5 years for a priority building in a high seismic risk area, to 35 years in a low seismic risk area.

When it comes to seismic strengthening, speak to EDC. We have designed earthquake strengthening for a wide range of buildings and would be happy to talk to you about options for your building.

Alterations to earthquake prone buildings

Any substantial alteration to an earthquake prone building will also require that the building be enhanced so it is no longer earthquake prone. A substantial alteration is at the discretion of the council, but will be works that requires consent, and has a value exceeding 25% of the buildings rateable value.

So significant alterations to an earthquake prone building may well trigger strengthening works, prior to the timeframes discussed above.

What are the health and safety implications of owning or working in an earthquake prone building?

Worksafe have issued a position statement “Information for employers and owners of workplace buildings”

Worksafe will NOT take health and safety enforcement action against you in relation to a building’s ability to withstand an earthquake, provided you are following the Building Act.

If your building is issued with an earthquake prone notice, and is within the timeframe to strengthen or demolish, then Worksafe will NOT take action against you in case of an earthquake related serious harm incident. Worksafe will not apply a higher standard than the Building Act.

Note: This applies only to the building structure. The fixing of items such as fridges, shelving or machinery is typically not covered under the Building Act. Chattels and equipment should be secured to prevent harm to a building’s occupants in case of an earthquake.