The approval will see various internal and external alterations and additions made. They include new theatre change and storage rooms, as well as a new commercial kitchen, amenities, store and office.

Fully-ducted, large-scale mechanical air conditioning will also be installed, as well as structural strengthening works and concrete flooring to the underside of the existing stage, feature lighting under awnings and ongoing conservation works.

Due to the site being listed as a state significant heritage item, councillors sought confirmation of approval from NSW Heritage before considering passing the motion.

"It is a two step process to getting heritage approval," director of community and business Grant Johnson said.

"We consulted with the heritage office in regards to development features and they gave general terms of approval in return, but we then have to go back to them with each piece of work we want to do inside the development application."

Councillor Pam Halliburton raised concerns over a lack of public toilets on Broadway Street, suggesting the upgrade to the theatre's bathroom may provide a sound alternative.

"I think we could look into utilising the Athenium toilets as public toilets," she said.

"The little area where the current kitchen leads into the toilets could become a public access path to the bathrooms to keep the area separate from the main building."

The allocation of a new office area also raised concerns among councillors as to its purpose, but Mr Johnson said the design would provide flexibility for future plans.

"None of us really know what might be before us in years to come, so it could be that we lease it in future, or it could become a booking office for the theatre, but at this stage it's just to add flexibility and allocate space in the design."