DEJECTED: Michelle Crouch wants to know why her new building performed so poorly in the earthquake.

The owner of one of Christchurch's newest building is demanding to know why it failed in Monday's quakes - just a day before it was to open.

MG Nails and Beauty modern purpose-built tilt-slab premises on Barbadoes St will have to be demolished after Monday's 6.3 magnitude quake, with part of the ceiling caving in and the walls shunted into a precarious angle.

Business and building owner Michelle Crouch said when it struck, two contractors completing the finishing touches inside were lucky to escape unscathed as part of the building collapsed. She believed if the quake had come a day later, when the shop was full of customers and staff, it could have killed someone.

Crouch is demanding to know how a new building signed off by builders, architects, engineers and the Christchurch City Council could perform so poorly in the quake.

"I want answers because I don't want this to happen to anyone else. If my girls were in there how would I be able to live with myself," she said.

However, the building's engineers said the buildings had performed above expectation under exceptional strain, staying upright and allowing the occupants to escape.

Crouch said she had sunk $400,000 into the building and while insurance should cover the loss she was unsure whether she could bring herself to rebuild.

"I'm not putting anyone down I just don't have any confidence in this sort of thing anymore. I don't even know if I want to rebuild."

She said she had warned others to stop and think before rebuilding their premises after the quakes. It is the second time Crouch has lost her business.

Her Fendalton beauty parlour was destroyed in the September quake.

She has been operating from her home since and was looking forward to restarting her business in a safe new modern building, she said.

The building has been under construction since before the September quake after Crouch demolished the previous building which was deemed too old to economically quake strengthen.

She claimed she was told by engineers the new building would be strengthened beyond the building code requirement, designed to withstand not only the impact of a strong earthquake but the possibility of a neighbouring building collapsing onto it.

After the February quake the building sustained some damage.

But it was cleared for occupation by engineers provided some remedial work was done, she said.

"The engineer came out and said it held up really well and did what it needed to do ....it cost about $95,000 to repair it."

Kirk Roberts Consulting Engineers Ltd director Stephen Roberts, who worked on the building, said it had been built beyond the building code requirement and even exceeded the new tougher standards being recommended by the Institution of Professional Engineers since the February quake.

While the building had been damaged it had remained standing during three quakes that greatly exceeded the building code requirements, he said.

"The building has performed exceptionally well for the current building code," he said.

The environment in Christchurch since February was well beyond what any codes had predicted and if asked now he would not recommend proceeding with Crouch's building.

In fact it would be unwise to build anything in Christchurch until the risk of further severe aftershocks had passed and there was a better scientific understanding of the fault lines beneath the city, he said.

The building's architect, Marcus Stufkens, director of Stufkens and Chambers Architects, said he was not happy about the building's performance but it was too early to say whether there was any fault.

Crouch had asked for the building's performance to be peer-reviewed, he said.