Unreinforced building total underestimated

Are we heading for a heritage disaster? Quite possibly.

There are signs of panic abroad and official pronouncements are being made based on woeful depths of ignorance.

An article in last Thursday's Otago Daily Times was headlined "3500 NZ buildings `need reinforcing"'.

It reported the urgent recommendation of the Royal Commission investigating building failures during the Christchurch earthquakes, chaired by Justice Mark Cooper, to take immediate steps to strengthen about 3500 unreinforced masonry buildings (URMs) throughout New Zealand.

Such was the commission's sense of urgency it made the recommendation before it began its public hearings.

That was rash because it is based on a report which grotesquely underestimates the real size of the problem.

If implemented thoughtlessly, it would either put a large dent in the Government's already battered accounts or impose a huge financial burden on local authorities and/or severely impact on the lives of people who own or occupy the nation's URMs.

Nowhere would be so badly affected as Dunedin, except perhaps Oamaru.

How did the commission make this mistake? It was concerned that in the February 22 earthquake, 42 people died as the result of the failure of URMs.

This was reflected in a report it had received which urged it to take just this sort of precipitate action over URMs.

However, the commission did pause to consider, as that report had not, the fact that 140 people died in buildings which were reinforced, mostly in two structures built in the 1960s and 1970s.

A number of still later-built reinforced buildings also spectacularly failed.

This has led some in the engineering fraternity to assert that even buildings constructed in the 1990s cannot be regarded as safe and that we need a sharp upgrade of present building codes.

Now, if every reinforced building in New Zealand constructed before, say, 1993 were to be compulsorily retrofitted to strengthen it, what would it cost and who would pay? I imagine by the time that suggestion got to Bill English and John Key's desks, someone would have hazarded a figure and those gentlemen would shake their heads and demur.

It would simply be too onerous. A lesser remedy would be sought.

But to go back to the URMs. The authors of the report put the 2010 value of their estimated 3750 URMs at NZ$1.5 billion.

They also opined to the commission that the cost of upgrading them to 67% of present codes might be about $2 billion.

That's the cost nationally, so it might not seem too eye-watering, but unfortunately it's wildly wrong.

The presentation to the commission was based on a 2010 academic article Prevalence of New Zealand's Unreinforced Masonry Buildings written by Associate Prof Jason Ingham in the civil and environmental engineering department of Auckland University and Alistair Russell, a PhD student there.

Prof Ingham kindly sent me a copy and I have discussed it with him. One glance at one figure shows it is deeply flawed.

In table 4 on page 191, it estimates that in the whole of Otago and Southland there are only eight URMs built before 1900.