The "twisted and shattered" Christchurch Cathedral is more damaged than first thought and the timing of its rebuild uncertain.
The February 22 earthquake cracked pillars, twisted walls, shattered stained glass, collapsed buttresses, fractured masonry and toppled the tower.
The treasured Rose Window on the west wall, the tower, the north wall and the south wall will have to be dismantled and rebuilt, engineering reports say.
"The glaziers hopefully will be able to restore that in some way and it will fit into whatever the new building is going to look like," Dean Peter Beck told ONE News.
Security footage has also emerged showing people were on the balcony at the top of the tower just three minutes before the quake struck.
Cathedral administration manager Chris Oldham said the true extent of the damage became clear only after staff returned to the site.
"The pillars inside have cracked and the whole building is actually in quite a sad way," he said.
"The building is twisted. It has moved. The buttresses have stones coming out of them. If you look at the wall on the south side, you can see how the top half of it has moved one way and the bottom half of it has moved the other way.
"The stained-glass windows are all twisted and shattered on that side.
"When you go inside, the Oamaru stone blocks have come away from the wall and are loose and at unusual angles."
The west porch has moved away from the west wall by about three centimetres. The top of the transept walls are offset by about 4cm and the north buttress of the west wall has collapsed.
The Rose Window is shored up with a steel gantry.
The state of the cathedral's foundations is still not clear, and any decision on a rebuild will be based on this geo-technical information.
Beck also said it is unknown how long the restoration would take and how much it would cost. A detailed assessment of the building has not yet been completed.
"There is still a lot we don't know about the state of the cathedral and how a rebuild will play out," he said.
"I have no doubt we will rebuild the cathedral, but in the meantime, as always, we listen to and seek guidance from both the church and the wider community.
We are deeply grateful for the many messages of support we have received, for the outpouring of love for the cathedral and all it represents."
No-one in the tower
In the weeks after the February quake it had been feared that 22 people had died in the toppled cathedral spire.
Cathedral staff later recovered security footage that revealed no-one was in the tower when the quake struck.
"We have security cameras in the tower and it is all fed into a computer in the back of the cathedral. The SAR [Search and Rescue] teams got that out and we were able to look at the footage," Beck said.
"It works by starting to record when there is movement up there."
"There had been no movement for three minutes before the quake. There had been nobody in the tower for three minutes. That is how we worked out there was no-one in the tower."
"I suspect that the tower held up long enough to enable those who were sitting around basking in the sunshine to scoot out of the way."