Restoration protects old block

The Hereford St office block had been previously damaged by fire. Photo / Supplied

When Christchurch businessman Mike Pero bought his arson-hit historic block in the city's CBD for $250,000, the first thing he thought about was demolition.

Fire services had partially ripped the roof off the block which once housed Americanos, a late-night club. Rats, pigeons and the weather had taken their toll on the Hereford St office block.

"I bought it in 1999 for the land, really, and everyone thought we'd pull it down. You should have seen it, it was in really bad shape. But I looked more closely at it and decided to restore it."

So the man who founded the eponymous mortgage broking business engaged engineers at Powell Fenwick Consultants and Peter Hawker Architects to devise a restoration and refurbishment plan for the Oamaru stone-faced building with stately arched windows, costing Pero $750,000 to bring it up to the 2000 Building Code.

Much of that prepared it well for this month's 7.1-magnitude quake, and the building suffered no damage.

A letter from Peter Hawker said the two-storey building had previously had severe internal fire damage and had been left open to the elements.

"The construction was triple-brick lower walls with double-brick upper walls. Exterior walls have decorative Oamaru stone detailing consistent with the period, interior timber floor structures and a bolted timber truss roof system. We were responsible for upgrading work to bring the building up to current regulations and allow the building to be used as a showcase for Mr Pero's head office," Hawker said.

A new structural system was installed within the existing external envelope to bring it up to current earthquake regulations, Hawker said.

A new reinforced concrete slab was laid around the ground floor and tied into the walls. A new structural steel frame was installed to support the existing second storey timber floor and roof structure. The underside of the upper floor had a plywood structural diaphragm installed. A new two-storey steel bracing frame was added to either side of the stairwell.

Structural strengthening was also installed around the perimeter of the parapet to prevent this toppling in an earthquake.