Expected toughening of New Zealand earthquake codes has this week cast doubt on the future of two of quake-hit Christchurch’s most historic buildings.
The Anglican Cathedral and Catholic Basilica structures, which were severely damaged in last year’s magnitude 6.3 earthquake, would face onerous rebuilds if New Zealand’s building codes are tightened as expected.
More stringent codes are expected following publication of a Royal Commission investigation into last February’s earthquake when they are published this November.
Current rules dictate that heritage buildings like the Cathedral and the Basilica will only be able to obtain buildings insurance if they can withstand 34% of loadings set out in the code. The Institution of Professional Engineers New Zealand (Ipenz) has recommended that this be revised up to 67% of code loadings, but the Royal Commission could recommend that it be as high as 100% (NCE 15 September 2011).
Ipenz chief executive Andrew Cleland accepted that heritage buildings would find it hard to comply with the strengthened building code.
“Even if heritage buildings are strengthened [to the current requirement of at least 34% of code] they may find it difficult to get insurance because of the increased strengthening requirements,” Cleland told NCE this week.
Cleland added that the cost of insurance could rise further if new building policy focuses more on protecting the general public outside the building instead of just those inside.
The issue was brought into sharp focus this week following the decision to demolish the city’s 131-year old Cathedral. The Basilica’s future is also uncertain. Continuing aftershocks - particularly those in June and December 2011 - keep damaging the remaining cathedral structure, putting it at risk of collapsing onto the city streets.
Bishop Victoria Matthews announced the Cathedral will be carefully demolished to a level of about 2m to 3m after
the Canterbury Earthquake Recovery Authority issued a Section 38 notice to ensure it was made safe.
A Section 38 notice can be issued to owners of buildings that are considered dangerous in accordance with the Earthquake Recovery Act.
The Anglican Church’s decision to demolish the structure caused a public outcry, not least because the engineering report on which the decision was based was not released to the public.
“There is a tome of information on which the decision was based and thus it is just not practical to release,” an Anglican Church spokesman told NCE.
Along with safety concerns, the Anglican Church said it cannot afford the NZ$100M (£52M) it would cost - on top of its insurance payout - to rebuild the cathedral. As a result the future of the Cathedral remains uncertain with the Anglican Church unsure whether it will even be will even be able to rebuild it in the same location.
A funding shortfall could also threaten the future of the Catholic Basilica where initial rebuilding costs are also estimated to be £52M.
“We are really looking at three options - whether to demolish the existing building; retain what we can of the Basilica and rebuild to its former glory; or, in the short-term, whether or not to mothball the building until we have a clearer picture,” said Cathedral Management Board chairman Lance Ryan.
Consultant Opus is advising on the Basilica solution as well as the city’s reconstruction. Rebuild manager Jon Fearnley said that unlike the Cathedral, the Basilica is not a risk to the public.