The Gloucester Street theatre has not opened since it was forced to close in 2020 due to the pandemic.
Last October, it was announced that the Grade 2-listed venue would remain closed until at least the end of next year after serious defects were discovered in its roof.
The £11.5m renovation cost – which will be met by taxpayers – was secured in this year’s Government Plan.
Now, the initial plans – which include improving fire safety, strengthening floors and replacing the glass front of the box office and dance studio – have been passed.
Wider plans for the site include repairing the auditorium’s dome, re-upholstering the seats, laying new carpets and improving disabled access.
Last October, a report commissioned by the Government set out a long-term future for the Opera House, which included the possibility of having resident arts companies, appointing an Executive Director on a salary of up to £100,000, and expanding into the public house next door.