The planning and land authority refused JWLand's Braddon Place proposal in January.

The $500 million development was proposed for land that previously housed the Northbourne flats public housing buildings, between Northbourne Avenue and Henty Street.

JWLand submitted a development application in mid-2022, initially proposing 602 residential apartments and 239 hotel rooms across six buildings.

In early 2023, JWLand amended the application, swapping the hotel rooms for 128 build-to-rent apartments.

During discussions with the ACT government, the build-to-rent component was later changed to a serviced apartment proposal.

Michael Prendergast, national head of development at JWLand, said the team had "mixed emotions" about the refusal.

"It was just unfortunate given the broader team had put in such a good effort over the last four years that there was a refusal at the end of that process," he said.

But the refusal clearly outlined what the team would need to change before submitting amended plans for reconsideration, Mr Prendergast said.

"We now know, in writing, what the government wants us to address, and we've obviously spent the last couple of months working on that," he said.

In its notice of decision, the planning authority noted the development was inconsistent with several planning and development codes.

Only three of the 602 residential apartments proposed were three-bedroom dwellings, which the authority said did not satisfy the requirement for a "combination of dwelling types".

Mr Prendergast said more three-bedroom apartments would be added to the plans.

The design proposal also included bedrooms with no windows and "snorkel-style windows", a term used to describe a narrow window at the end of a long corridor within a room.

"The proposal includes bedrooms without windows, 'snorkel' style windows, and insufficient shading to west facing windows, which does not meet National Capital Plan requirements," the notice of decision stated.

Mr Prendergast said these windows were likely included in the serviced apartment component of the project and would be amended.

The Conservator of Flora and Fauna did not support the proposal due to the removal of regulated trees.

Plans for tree removal "ignored" advice from the National Capital Review Design Panel to retain as many trees as possible, the notice stated.

JWLand will retain additional trees in the revised plans, however Mr Prendergast said many trees on the site were not of high quality.

The proposal also failed to meet the requirement for one visitor car parking space per four dwellings, the authority stated.

It noted for 602 residential units, just 12 visitor spaces were provided, a "significant departure" from the 151 visitor car parks required.

The number of visitor car parks will be increased, Mr Prendergast said.

JWLand purchased the 15,607-square-metre block of land from the Suburban Land Agency in 2020 for $28 million.

The deal came after the ACT government failed to sell the land in 2018.

The site was previously home to the Northbourne flats, part of a broader public housing precinct on Northbourne Avenue that was sold in stages by the ACT government.

Mr Prendergast said the refusal delayed the supply of homes, including 90 affordable dwellings, even longer.

"I don't think anyone would have thought that in 2024, the site would still be without [development] approval," he said.

"This delay ultimately delivers a knock-on effect that is more broad than what is being experienced by our organisation and I think that key point is often disregarded."

JWLand expects to resubmit plans for Braddon Place in the coming weeks.