Central Auckland's tallest apartment block is yet to get out of the ground because of flawed concrete in its foundations.
The contractor China Construction New Zealand has been struggling to investigate and fix the defects at the Seascape building on Customs Street East for more than a year.
The five-storey-deep walls of the carpark basement have voids in them and are contaminated by slurry.
Some concrete on the inside walls of the basement has been waterblasted and patched with structural concrete, but the outer face of the walls is buried in earth and has yet to be properly checked.
The 52-storey Seascape had aimed to open its apartments in 2021, sitting on massive piles, a thick slab, and the basement walls that are well below the level of the sea just 200 metres away.
Auckland Council said it was aware of the risk from seawater getting in and corroding the reinforcing steel.
It had allowed carpark floors to be built only up to a mark five metres below ground level.
"At this point we would not allow work to proceed higher unless we are satisfied that area of wall is compliant," the council said.
The contractor found defects and promised a quick fix back in October 2018 - back then, it said the concrete was "just a bit patchy".
Fourteen months on, Auckland Council is still waiting for key information about the state of the outside face of the walls.
Asked if whole new foundations might be needed, the council said "no", but added if the outside of the walls needed "extensive" repairs, then "other options may be looked at".
It was "anticipated" the outside face of the walls would have the same defects as the inside faces, the contractors and developer said.
But they insisted the defects were isolated, were anticipated, and could be fixed with methods regularly used worldwide.
The walls themselves were being monitored "and these have performed as expected", the contractor and China-owned developer, Shundi Customs, said in a joint statement to RNZ.
However, construction would not begin above ground until the defects were fixed, they said.
"Shundi has dedicated Seascape development as its contribution to Auckland city. With the appointment of reputable contractors and consultants, and under the supervision of local authorities, Seascape aims to deliver a product that is of high standard and quality."
Three of the companies involved with the basement are controlled by the French multinational Vinci:
• March Construction, which built the walls using a new drilling technique.
• Another Vinci company, Soletanche Freysinnet, is repairing the walls.
• And a third Vinci company, Sol Expert, investigated the groundwater effects, including of saltwater.
Sol Expert's findings are in a remediation report prepared by China Construction.
Independent experts were reviewing that report and should provide their assessment by Christmas, the council said.
"We are waiting on further information ... before making a final decision," said the council's manager of field surveying, Jeff Fahrensohn.
"Once we have completed our review we will take any required action deemed necessary to ensure compliance."
It repeated the companies' assertion that the problems were confined to the top five metres of the basement walls, without specifying what evidence it has of this.
The council did not respond to questions about whether any independent investigations had been done on site.
Patching the inside walls had been effective, the council said. "Engineers have certified that the wall's structural integrity has not been compromised.
"Please keep in mind that the D-wall [diaphragm] does not support the tower structure."
Shundi did not say if the timeframe to finish Seascape had changed.
It rejected a comparison with the nearby Hengyi Pacifica tower, that is almost as tall, was started about the same time and was three-quarters finished, with Shundi noting the Pacifica did not have a big basement.
As for near-neighbours of the Seascape, "there is a comprehensive monitoring program in place... at this stage, nothing indicates any compromise to buildings surrounding the site", the council said.
Investigations of the outside faces appear to consist of drilling cores from the inside-out, reducing impacts outside Seascape's footprint. It is unclear how these cores can be drilled far enough through, with so much reinforcing steel in the way.
Freyssinet New Zealand referred RNZ's queries to China Construction.
The building has additional problems: Two piles sunk 29m from ground level into rock, have been built 400mm out of position at the bottom.
The builders are having to thicken the foundation above and add extra anchors to other piles.
The council did not expect to sign off the foundations until late next year.
Also, the tower's fire design has still not been finalised, after two years of wrangling, and being rejected for not giving firefighters enough access in top floors.
A fire design strategy has now been agreed on for when building consent for that stage is lodged.