Trust chairman Steven De Graaf said the architect and the engineers had everything drawn up and the project was looking "pretty good".
"There’s just a couple of things to finalise.
"We’re going to put in for a resource consent very soon for stabilisation."
Once resource consent was received, a major fundraising project would begin.
He said more than $1million would be needed for the project, and it could take a year to raise the money.
It was hoped some of that money could be raised by taking small groups on guided tours around the castle.
At the moment, the castle remains closed to the public until the project is completed.
The stabilisation work itself was expected to take about six months to complete, and he estimated the castle could be open to the public by mid to late 2022.
"It’s quite exciting, what we’ve got planned.
"Once opened, people are going to be able to have a walk around inside the building.
"There’s going to be some stairways and landings and they can actually get up to the top, behind the tower, so they can look down the coast and out towards the city.
"There will be a bit more of a view than just standing looking at the building.
"It’s more than just some steel frame around the building.
"Some people suggested locking it all up and putting windows on it so no-one can get in, but we’d rather people can actually walk around it and get into where the floors and stairs used to be."
Mr De Graaf said the trust was still working out whether access to the castle would be via guided tours with volunteers on certain days, or open permanently during daylight hours for people to roam through unsupervised.
The trust was also working with the Dunedin City Council on a walking track from the castle to Tunnel Beach.
"Hopefully, that will be finished at a similar time to the castle, so that it will become more of a destination for tourists."
