Buyers are still keen on Auckland's earthquake-prone buildings, despite the cost of strengthening them potentially spiralling into tens of millions of dollars, a mortgage adviser says.

Owners of the nearly 2000 - mostly commercial - buildings have 35 years to strengthen their properties, or 45 years in the case of heritage buildings.

Many are making use of this to delay the expensive works or instead look for buyers, Loan Market Auckland's Bruce Patten said.

And - despite most banks refusing to lend to those purchasing quake-prone buildings - he pointed to recent buyers of a Kingsland commercial building as a sign the market was strong.

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While the banks would not lend against the building because it was quake prone, Patten helped the buyers pay for it by instead drawing loans against other properties they owned.

The buyers were happy because they thought the building was otherwise structurally sound and would keep rising in value, allowing them to delay retrofit works until closer to the deadline or to sell before then.

"I don't think the [requirement to strengthen buildings] is severely affecting the market because there is a real shortage of good commercial stock," Patten said.

"People are tending, in Auckland, to overlook the costs."

Yet the cost and problem of managing the city's quake-prone buildings seems likely to only continue escalating in coming years, given the vast number of affected properties.

Assessors looking at 8000 buildings across the city, as part of a process which started in 2011, have deemed about 1800 potentially quake prone.

The Leys Institute in Ponsonby is hailed as Auckland's oldest suburban library but will also need strengthening work after being deemed earthquake prone. Photo / Adele Krantz
The Leys Institute in Ponsonby is hailed as Auckland's oldest suburban library but will also need strengthening work after being deemed earthquake prone. Photo / Adele Krantz

Under legislation introduced in July last year, owners must now display formal notices in these buildings, advising that they are quake prone.

Auckland Council began last November sending letters to the owners, telling them to display the notices, and was now halfway through the process.

The first letters went to Puketapapa Local Board area owners before progressing to Devonport-Takapuna, Albert-Eden and now the Waitemata Local Board area.

Upon receiving the letters, owners wishing to challenge the assessment their building was quake prone have one month to do so.

Most affected buildings are commercial, but some were mixed use, such as those along historic Dominion and Sandringham Rds, which have ground-floor businesses and upper-storey residential spaces.

Some large accommodation buildings, such as hostels, have also been affected, while the public will have to foot the bill for strengthening Auckland Council properties.

It has identified nine public buildings requiring strengthening work, including the Victoria Theatre in Devonport and the Grey Lynn Library and Leys Institute Library in St Marys Bay.

Yet that number is likely to swell, with the council's general manager building consents Ian McCormick saying another 50 publicly-owned buildings had also passed through initial "high-level assessment" stages "to start detailed retrofit design works".

Regular "mum-and-dad" suburban homes, on the other hand, were exempt from the checks and legislation.

Putting a figure on the total cost facing the city to fix all of its quake-prone buildings is near impossible, University of Auckland engineer Dmytro Dizhur said.

That's because the costs vary from building to building, and was a bit like visiting a doctor.

"You can always get a second opinion. It really depends on the person who is assessing the building and their expertise," he said.

"Same goes for the retrofit design. One engineer might have one philosophy and another might have a completely different view."

Dizhur pointed to a three-storey Wellington building whihc he was asked to give a second opinion on after the owners were given an initial $1.6 million quote to strengthen the property.

He said he was able to cut the bill by $1m as he successfully strengthened the building to meet modern standards at a cost of $600,000.

The Victoria Theatre in Devonport after refurbishment works in 2010. Photo/Sarah Ivey
The Victoria Theatre in Devonport after refurbishment works in 2010. Photo/Sarah Ivey

University of Auckland researchers were hoping to similarly cut costs for other building owners by devising and widely sharing simpler retrofit designs and techniques, he said.

These designs try to make greater use of a building's existing structures - as opposed to knocking down walls - along with "off-the-shelf" materials that builders can easily buy and use.

This allows engineers and builders to work faster and reduces the amount of time a building sits vacant.

"Because that is another quite substantial cost - the cost of the building being vacant - and so the quicker you can get the work done the better," he said.

And while the costs could be near prohibitive for some small business owners, the new legislation was not always a burden.

Dizhur said quake-strengthening work had propelled some owners to invest more to rejuvenate their buildings, and even business districts.

"When you have a construction team going in to do a retrofit, I see some clients who use that opportunity to modernise and utilise the building space better," he said.

"It gives new life to some buildings and allows them to be better used."