He asked whether any alternative had been considered to having such as ''hard junction''.
Cr Bill Grainger also questioned the need for the dogleg in the promenade and loss of grass.
Mr Jones warmed that the project was very complicated and there would be flow-on effects of looking at this aspect of the design in isolation.
It could impact on the resource consent from the regional council and force the council to go through a new publicly notified consent process rather than it being treated as a variation to the existing consent.
He explained that the promenade's sharp turn around the tidal stairs was designed as a slow-down for cyclists and skateboarders so people could safely mingle at the top of the stairs.
Mr Jones also warned that starting the tidal steps further out into the harbour in order to save the grass would increase foundation costs.
"The ground conditions are not great."
A two- to-three week delay to revisit the design also meant the tidal steps would not be built inside the construction season and would miss the summer, leaving it as a construction site until work resumed at Easter.
City transformation manager Jaine Lovell-Gadd said it would jeopardise where they were heading with the timeframe to build the tidal stairs.
Meeting chairman Kelvin Clout asked if the existing plans could be retained if there was a smaller trimming of the grassed area, maybe by half.
After hearing the difficulties posed by a big review of the design, Mr Crosby signalled he would accept a small modification.
"I don't wish to delay the project."
However, he said there was room for a further conversation, without it being onerous on the design and budget.
Ms Lovell-Gadd interpreted the debate as the council asking for minor changes to the area around the grass, but no major changes.
The council was told that for a complicated project like the tidal stairs, the design fees and geotechnical investigation costs typically ran at 14 to 16 per cent of project costs. Design and geotech costs were $523,000 for the project.