How much of the Ontario Science Centre roof is at risk of collapsing? See for yourself

Questions have swirled for the past week about why the Ontario Science Centre was suddenly and permanently closed on June 21.

The province has said engineering reports it commissioned from Rimkus Consulting Group show the 55-year-old roof could give way to snow and collapse. As a result, the government moved to close the building now, to decommission it by late October.

"This was a warning — a health and safety warning — and, as a representative of government, I have to take that seriously," Infrastructure Minister Kinga Surma told reporters at a news conference Monday.

But four engineers and architects told CBC News that what's been said about the reports, and what's in the reports, don't match — and closing the building could've been avoided.

"There is no immediate danger," said Yasser Korany, a forensic engineer with KSI Engineering, a firm that examines structures that fail.

"There is enough time to really examine the information," Korany said.

Here's a breakdown of what was in the reports that led to the Science Centre's closure — and what experts think about the decision to close the building.

Last year, over 100 schools in the U.K. had to fully or partially shut down after safety concerns connected to reinforced autoclaved aerated concrete (RAAC).

That prompted Ontario to review RAAC in its public buildings, as the material was used widely from the mid-1950s to the mid-1970s, according to the Rimkus reports.

RAAC is a lightweight material, but is also weaker and has a shorter lifespan than normal concrete.

"It is prone to a lot of damage," said Sam Adu-Amankwah, an associate professor of civil engineering at Aston University in Birmingham, England. He said proper maintenance is key when using RAAC.

RAAC has been used in hundreds of other aging public buildings across Ontario, but only the Science Centre has been forced to close.

Rimkus inspectors visited the Ontario Science Centre between Dec. 6, 2023, and March 26, 2024, according to its reports.

The engineering reports review the centre's three buildings separately: Building A, where the main entrance is, Building B, which features the Great Hall, and Building C, the largest building with numerous exhibits.