The DHB said the current zone does not support "current and future hospital activities" and it has to apply for resource consent each time there is a new development which limits its ability to appropriately plan for the hospital's future development.
The desired outcome is to ensure new building projects can occur within a defined development envelope.
Two public open days, today and Saturday, give the public the chance to view the future options drawings and ask questions about the rezoning proposal.
The work to redevelop the hospital will be subject to government funding and will likely take place in stages over the next 15 years.
The need for a major upgrade of the ageing hospital was highlighted in the DHB's 2016/17 annual plan. In May this year, the board got approval from the Government's Capital Investment Committee to present business cases.
The DHB would not be drawn on the cost, although the process the board is undergoing is indicative of the project's size.
Treasury investment in health infrastructure projects in excess of $15 million require GCIC approval, above Cabinet or ministerial approval.
Once the plan change application is lodged with the council, it will be publicly notified. Anyone can make a submission and request to be heard by the committee.
Once a decision is made, any submitter or the DHB can appeal the decision to the Environment Court.
The open day tomorrow is on from 5pm to 8pm and on Saturday from 9am to 12pm at Tohorā House - the entrance from the end of West End Ave.