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An Olympic Installations Board report says the Olympic Stadium's roof is not considered safe following a snowfall of more than eight centimetres. ((Paul Chiasson/Canadian Press))

The roof of Montreal's Olympic Stadium is in such poor condition that the city's fire department is threatening to shut the building down, CBC News has learned.

The roof has lost 45 per cent of its resistance to tearing and requires frequent repairs, according to a recent Olympic Installations Board (OIB) report obtained through an access to information request.

The membrane roof, installed by Birdair in 1998, rips 50 to 60 times a year, the report says.

The roof is not safe enough for events to be held any time there has been a snowfall of more than eight centimetres, the report says.

There are also questions about the potential effect of a heavy rainfall.

The report discusses the importance of maintaining "palliative measures" already put in place, including drainage for the roof and a snow-melting system.

'It's really been aging in 10 years and this is not normal'— Pierre Carreau, University of Montreal

The Montreal fire department has warned it might have to close the stadium if the OIB doesn't address a number of priorities, including replacement of the roof.

"If found that one of the priorities cannot be maintained, our service, for reasons of public safety, would be obliged to terminate the agreement and consider the permanent and final closure of the Stadium," the department wrote in a letter dated Aug. 8, 2009.

Roof easily cut

Ultraviolet rays and Montreal's cold and snowy winters — flagged as a problem when the roof was built — are behind the roof's deterioration, said Pierre Carreau, a professor at the École Polytechnique, the University of Montreal's engineering school.

Carreau, an expert in plastics and composites, has studied the roof's material in his lab.

It was relatively easy to cut the material with a small knife, such as an exacto knife, he said.

"It's really been aging in 10 years and this is not normal," he said.

"As soon as there is any snow on the roof, you will have to close it because of this security reason. They have to close it — I would not take any chance."

Jacques Proteau, assistant chief of the Montreal fire department, agrees.

He was at the stadium in January 1999 when the newly installed roof ripped, spilling tonnes of snow into the building, where workers were setting up the annual Montreal Auto Show. There were no serious injuries.

"Analysis from specialized firms are showing us the weight that the roof can support," said Proteau. "The roof is worn.… The number one solution … is that the roof must be replaced in the shortest delay."

Ongoing problem

The stadium has been an ongoing problem for the OIB.

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In January 1999, the Olympic Stadium's roof tore, spilling tonnes of snow into an area where workers were preparing for the city's annual auto show. ((CBC))

The oval building with its arching tower and planned retractable roof was not completed in time for the 1976 Olympic Games.

In 1987, it was finally capped with a cable-supported Kevlar roof, which was also prone to tears.

The current Sheerfill II roof was installed in 1998, at a cost of $37 million.

Despite corrective measures implemented over the year, the stadium's floor is not used for activities from December to March.

In 2000, the OIB sued New York-based Birdair for damages in connection with the 1999 collapse of the roof.

The provincial government in 2004 awarded SNC-Lavalin a contract to replace the roof, but nothing has been done.

The OIB declined to comment on the report.

A spokesperson for the province said the roof of the stadium is a priority and an announcement is expected before the summer.