In a ruling Tuesday, Commissioner Paul Belanger also rejected a confidentiality request from a professional engineering association related to complaints and disciplinary measures taken against engineers involved with the Algo Centre Mall.
"The open-court principle is of particular importance in the context of this type of public inquiry," Belanger said.
In their application, mall owners Robert Nazarian and his son Levon argued they had given the commission sensitive financial statements to back their bid for taxpayers to pay their legal bills at the inquiry.
Belanger refused to recommend such funding, saying the evidence they presented was "wholly deficient."
In also rejecting their secrecy bid, Belanger said his decisions would be subject to public scrutiny and therefore had to be transparent.
He said the Nazarians' financial situation would be relevant to the probe into the collapse, which killed two women, given that mall upkeep and maintenance costs would be scrutinized.
"The mall owners' financial circumstances are directly relevant and of significant importance," Belanger said in his ruling.
He also said they had not shown how they would be harmed by public disclosure of the documents.
The commissioner did make one concession — to delete their social insurance numbers from the paperwork.
Normally, material deemed relevant to the inquiry's proceedings would form part of the public record and several parties — including media outlets — opposed any secrecy on the grounds they could undermine the hearings.
The inquiry is delving into what caused the mall's rooftop garage to partially collapse last June and the emergency response to the tragedy.
Residents had long complained about leaks and other problems, but the owners have said the mall was inspected regularly and no serious structural deficiencies were found.
The inquiry, which is expected to begin hearings in March, also ordered the Association of Professional Engineers of Ontario to produce documents related to complaints about some engineers.
The association balked, saying it had to respect its own confidentiality requirements.
At a hearing in December, it changed its position to say the commission should notify any affected individuals to allow them to make submissions before documents were disclosed.
Belanger rejected that argument, saying it was impractical and the association had "made no effort" to show a secrecy order was really needed.
He also said two engineers, Greg Saunders and Robert Wood, could object to the introduction of any particular piece of evidence.
Wood and Saunders were employed by the engineering firm M.R. Wright and Associates that inspected the mall before it collapsed.
The commissioner gave a strong nod to ruling in favour of openness in cases where "conflict arises between the expectation of privacy or confidentiality and the open-court principle."
Case law, he said, has now "unquestionably and conclusively established" that transparency prevails except for exceptional cases where someone can show that would be harmful.
"The applicants have failed to discharge that onus," he said.