Staged restoration of the exterior of the complex is to start with the municipal chambers and the project will include repairs and maintenance of the town hall.
A seismic upgrade will also be carried out.
Documentation about safety barriers provided some information about the broader work to come.
"The applicant has indicated that the exterior restoration work is expected to take four to five years, but it is not possible to estimate the cost and timeframe of the seismic upgrade at this point," it was stated in a planning report.
It was possible the barriers would be up for longer, the report said.
"While the restoration work is under way, a full seismic assessment of the building will be undertaken to develop strengthening schemes."
The outcome of the seismic assessment could determine how long the construction barriers remain in place.
It was expected that as exterior work was completed on the complex the barriers could be "progressively retracted".
The municipal chambers in the Octagon opened in 1880.
The town hall, behind the chambers, was built in 1929.
Ornamental Oamaru stone fell from the chambers building in 2020 and thorough checks were carried out.
In 2022, the council said it was in a "discovery phase" — using both external and internal modelling — to understand issues.
Council meetings were shifted out of the chambers to the Dunedin Public Art Gallery, where they are still run, to avoid noise and disruption.
A council spokesman said investigative work and careful planning for the remediation of the town hall and municipal chambers was continuing.
"As with the recent Dunedin Railway Station upgrade, this is an important and high-profile project for our city," he said.
"It will be a complex project, and so we want to make sure we do due diligence to ensure we have the best plan in place for this significant civic building."
Installing construction hoardings around the site was the next step.
"The hoardings around the municipal chambers and town hall will ensure safety for our community and contractors as work is undertaken."
Scaffolding would be erected, as well as construction barriers along the Moray Pl and Harrop St perimeters.
The barriers would be roughly up to a storey in height and painted a dark "red shale" colour to minimise adverse visual effects on the appearance of the Octagon commercial heritage precinct, the planning document said.
