Hundreds of buildings with Science Centre roof panels remain open

The same lightweight concrete roofing material blamed for safety risks at the Ontario Science Centre is used in hundreds of other aging public buildings across the province, yet officials haven't pointed to any others that have been ordered closed.

The revelation comes as critics question whether the findings of an engineering report on the science centre's roof justify the Ford government's move to close the 55-year-old Toronto facility to the public with less than two hours notice. 

Much of the roofing at the Ontario Science Centre is made of reinforced autoclaved aerated concrete (RAAC), a material widely used in the construction of flat-roofed buildings throughout the 1960s and early 1970s. 

Although the province has for months been investigating the status of RAAC in Ontario schools and other public-sector facilities, and has identified it in some 400 buildings, all but the science centre remain open, CBC News has found.

An engineering report delivered last week to the province found a small percentage of the centre's RAAC roof panels have degraded to the extent that they're at high risk of collapse come winter. 

Despite this, the engineers did not specifically recommend immediate closure of the facility. However, the province's Ministry of Infrastructure urged the Ontario Science Centre board of trustees to shut it down immediately, a move announced Friday afternoon.

The province began looking at RAAC in public buildings in Ontario last fall, after more than 100 schools in the U.K. were ordered fully or partially closed over safety concerns. 

CBC News asked provincial ministries that oversee the largest portfolios of real estate for the number of buildings with RAAC roofing, their state of repair and whether any have been closed because of safety risks. 

Infrastructure Ontario has conducted an initial review of 190 provincial government buildings — such as courthouses and offices — that were built around the province in the era of concern, roughly 1955 to 1975. 

That review ruled out the presence of RAAC in more than half, with further investigations in the coming weeks on 79 buildings — 49 of which are currently occupied, said Michael Lindsay, Infrastructure Ontario's CEO. 

None of them have been ordered vacated, and Lindsay said he does not anticipate any will. 

"Ultimately we'll always be guided by the opinion of professional engineers on health and safety," Lindsay said to reporters on Friday. 

"I want to stress that all of the mitigations and monitoring that we've put in place for the Ontario Science Centre are also in place for those facilities, so there's already enhanced management of rainwater and moisture on roofs." 

In addition, about 8 per cent of Ontario's 4,800 schools have the material, but no school has been ordered closed as a result of RAAC safety concerns, said a Ministry of Education spokesperson.