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The owners of John Wickliffe House are livid the Dunedin City Council has declined their resource consent application to repair and paint the building, and say the owners of other concrete commercial buildings in the city should be very concerned.
The Princes St building, owned by Plaza Property Trust, has been hit with a common phenomenon known as spalling, or ''concrete cancer'', which causes precast concrete facade panels to crack and partly crumble, causing fragments to fall off.
Trust director Tony Offen said the concrete panels that formed the horizontal bands of the building, were cast with reinforcing steel inside, before being surface-ground back to expose a pattern of darker aggregate.
''Unfortunately, this has left the layer of concrete covering the steel too thin to prevent moisture rusting the steel.''
The industry standard technique for repairing concrete cancer involves removing the damaged concrete (up to 25% of each affected panel in some cases), rust-treating the steel rods, then applying an epoxy-based mortar to replace the removed material.
Then the panels must be waterproofed using a special-purpose pigmented elastomeric coating system which covers the repair patch to produce an even finish.
''However, the council's decision says that no painting under any circumstance will be acceptable on John Wickliffe House,'' Mr Offen said.
The decision surprised the trust because the vast majority of concrete buildings (and some stone ones such as the BNZ building) in the Princes St townscape precinct had already been painted.
''This is a technique that has been used and proven in various prominent buildings around Dunedin, including several at the University of Otago and Forsyth Barr House.''
Mr Offen said the council had asked the trust to accept ''a higher level of uncertainty'' and experiment with alternative techniques.
''Those alternative techniques may or may not require future resource consents; will not have the benefit of acceptable product and applicator warranties; and will result in a patchwork finish to repaired panels.
''To top it all off, pursuing the council's preferred option will at best, cost twice as much as the accepted industry practice.
''The trust cannot see how any responsible privately funded commercial building owner could justify going down that path.''
Mr Offen said the council's decision was very disappointing, but what was of most concern was the impact of the decision on other building owners in the city centre.
''The owners of concrete commercial buildings in Dunedin should be very worried.''
In their decision, council consent hearings committee councillors Kate Wilson, David Benson-Pope and Aaron Hawkins said they were not convinced painting was the only solution,
repairs should blend with the rest of the panels and clear-coat silicone waterproofing should be investigated.
The committee said the building's West Coast serpentine stone panels blend well with other concrete and stone finishes on nearby buildings, including the chief post office building and Consultancy House.
''It is the committee's view that painting these stone-faced panels would have a substantial adverse effect on the Exchange environment, whatever colour scheme was used.''
The trust has the right to appeal the decision in accordance with section 120 of the Resource Management Act 1991.