The State Commission Assessment Panel (SCAP) will on Wednesday assess long-mooted plans from the Freemasons Hall Trust to build a new “Keystone Tower” behind the state heritage listed Grand Lodge of Freemasons Adelaide Masonic Centre.

The $400 million project features a 238-room hotel to be delivered under Marriot International’s Westin Hotels brand, as well as office space, a business lounge, function area, “wellness centre” and an observatory on the top levels.

The Keystone Tower. Image: Walter Brooke and Associates and Freemasons Hall Trust via PlanSA

A new Adelaide Museum of South Australia’s History is also slated for within the Freemasons Hall and the first five floors of the skyscraper.

The development plan will require demolition of the Great Hall located at the rear of the Grand Lodge, while retaining the state heritage listed building’s frontage.

In a report published on Friday, government planning officer Ben Scholes recommended the SCAP approve the project.

“The proposal is considered to respond appropriately to the relevant objectives and policy outcomes anticipated by the Planning and Design Code related to retention of heritage places, design and appearance, contributions to the public realm, interface conditions and environmental matters,” Scholes wrote.

Internal and external drawing of the Grand Lodge revamp. Images: Walter Brooke and Associates and Freemasons Hall Trust/supplied

“On balance, the development is not expected to result in unacceptable impacts given the broad intent of the Code’s Capital City Zone policy and therefore, conditional planning consent is recommended subject to assignment of reserve matters.”

If constructed, the Keystone Tower would be Adelaide’s tallest building at 183 metres, eclipsing current title holder, the Crowne Plaza on Frome Street, by 45 metres.

The proposed development site, 254 North Terrace, is located within a CBD precinct noted for its high-rise development. Directly to the east is the 37-storey, 138-metre Crowne Plaza building and the 26-storey, 118-metre Yugo Adelaide City student accommodation tower.

The site location of the Keystone Tower. Images: Walter Brooke and Associates and Freemasons Hall Trust/supplied

Scholes said the high-rise development in the locality means the Keystone Tower “is not considered to be a significant departure from the recommended built form outcome”.

“The development would form a notable element of the skyline and be a landmark building in the city clustered among existing multi-level buildings along the North Terrace boulevard, responding positively to local context and satisfying the intent of Zone,” he said.

The Keystone Tower is located within a high-rise precinct of the CBD with no prescribed maximum heights. Images: Walter Brooke and Associates and Freemasons Hall Trust/supplied

The government planning officer also said the building’s location at the rear of the Grand Lodge “would provide an appropriate and relatively neutral built form addition”.

The Grand Lodge was erected in 1927 and added to the state heritage register in 1984.

Freemasons Hall. Photo: Tony Lewis/InDaily

The state government’s heritage authority, Heritage SA, ruled that the proposal to demolish the Great Hall at the rear “is not considered to be unacceptable”.

The state government and the developer have also reached an in-principle agreement to undertake conservation works to the Grand Lodge.

Heritage SA’s principal heritage architect, Michael Queale, said the Grand Lodge conservation works “are urgent and required as a priority”.

He also said that the developer demonstrated that construction of the Keystone Tower could not occur without demolishing the Great Hall.

“The proposed 37 storey tower directly behind the Grand Lodge building is of substantial scale, but is set clear behind the Lodge building,” Queale wrote.

The interface of the Grand Lodge and the Keystone Tower. Images: Walter Brooke and Associates and Freemasons Hall Trust/supplied

“So the established scale and proportions of the Grand Lodge section of the heritage building remain intact and are still evident from North Terrace streetscapes.

“The tower will be clad in a neutral glass façade, providing a visually neutral backdrop to the State Heritage Place.”

The Keystone Tower will be made up of a façade glazing system that will transition from opaque to transparent at the building’s upper levels, according to the planning report published on Friday.

Development consultants Future Urban, who are managing the development process for the Freemasons Trust, dismissed concerns the glass façade of the tower will reflect unreasonable levels of light.

“Although the replacement building will reflect light, the discomfort caused by these reflections when viewed directly will not exceed that experienced with other similar buildings in Adelaide’s CBD, and will be limited in time of discomfort to any one location,” Future Urban said.

The ground level of the Keystone Tower will hold an entry lobby and a shop, while levels one to five will be reserved for the proposed Adelaide Museum of South Australian History.

A hotel bar and restaurant is slated for level six followed by the hotel lobby on level seven and a fitness centre, swimming pool and bar on level eight.

A floor-by-floor breakdown of the Keystone Tower. Image: Arup

Wellness facilities are planned on level 10, a business lounge and business suites on level 11 and a plant room on level 12.

The 238-room hotel will make up the bulk of the tower from levels 13 to 29, with each of these floors holding 14 hotel rooms.

An office tenancy is slated for level 30. The planning report states this floor is “expected to be tenanted by representatives of the applicant”.

Another function area and bar is planned for level 31 below a three-level public viewing platform featuring an observatory, mezzanine and balcony from levels 33 to 35.

The Freemasons estimate that 914 people would visit the observatory levels each day, between opening hours of 7am and 11pm, according to the planning report.

The developers also predict more than 1600 daily visitors to the new museum, to be delivered and managed by the History Trust.

The tower proposal still requires Commonwealth airspace authority approvals given its height, although Adelaide Airport has indicated it does not oppose the application.

The Freemasons have previously stated their intention to complete the building in 2026.