Tenants tough on quake-proofing

Many tenants now want to know more about the risk of renting buildings. Photo / APN

Commercial property tenants in Auckland are far more aware and concerned about the ability of the buildings they occupy to withstand earthquakes, says an international engineering company.

Craig Stevenson, technical director of Aurecon which offers specialist engineering and management services to government and private clients, says office tenants have a "strong reluctance" to remain in buildings that are considered earthquake-prone or rated less than 34 per cent of the new building standard (NBS).

"This has especially applied since the recent central North Island earthquake events," Stevenson says.

Aurecon, with offices in 26 countries, has been involved in projects in more than 80 nations and employs around 7500 people across 11 industry groups.

Stevenson said some corporate tenants would now not move into a building assessed at less than 80 per cent of NBS and many were commissioning their own engineering consultants to review the assessments undertaken by the building owners to confirm all was in order.

"Building owners are starting to take action sooner rather than later to ensure they retain their tenants. For some organisations a higher percentage NBS is being looked for as a minimum - that is, 50 per cent of NBS, 67 per cent or even 100 per cent. This is pressuring some building owners to take action now.

"In our experience, some tenants are requiring a minimum percentage of NBS because of their business continuity requirements or the specialised equipment they want to protect.

"Government, health, and emergency services tenants may require a high percentage of NBS because they have to be immediately operational after a disaster event due to their post-disaster responsibilities."

Stevenson says Aurecon has received a greater number of inquiries and requests for specific information, particularly from property owners in the main centres. "This usually takes the form of a detailed engineering evaluation or detailed seismic assessment that provides a much better basis for making decisions about the future of a building."

Previously an initial evaluation procedure had sufficed for many building owners and tenants. "An IEP is a 'tick the box' process that is quick and easy but it doesn't involve any analysis of the building," says Stevenson. "So, the results can be somewhat misleading and it's not a sound basis for making serious financial decisions about a building.

"There is increasing recognition by building owners and tenants that an initial evaluation procedure isn't necessarily reliable. It can often miss issues relating to design and construction likely to impact on the structural performance of the building.

"We're finding that where concerns regarding the structure are identified as part of an IEP assessment, a more detailed seismic assessment is subsequently being requested by the building owner to address this."

He says detailed engineering or seismic evaluations include:

a description of the building

a description of the structure and how it resists loads

detailed analysis of the strength of the structural elements which form the building's skeleton

formulation of a failure mechanism and understanding of this

identification of structural vulnerabilities that might cause premature collapse

recommendations as to whether the building should be strengthened generally, including high-level comment on what might be appropriate.

Stevenson says landlords with buildings less than 33 per cent of NBS will have to undertake strengthening within 20 years of proposed legislation taking effect.

The new rules would provide a maximum five-year assessment period followed by strengthening within 15 years of assessment. Buildings with higher risk elements will be prioritised and heritage building owners will be able to apply for time extensions.

Landlords don't have to strengthen buildings if they're already between 33 per cent and 67 per cent of NBS.

However, the NZ Society for Earthquake Engineering recommends all buildings are strengthened to a minimum of 67 per cent of NBS and preferably as close as reasonably practical to 100 per cent NBS.