Once one of Canada's best preserved heritage homes, the Mount Stephen Club is in danger after it suffered severe structural damage due to a hotel development project.

Considered a jewel of Canadian architecture, the Victorian mansion was once the home of Lord Mount Stephen, one of the founders of the Canadian Pacific railroad.

“The house dates from the 1880s. It's a spectacular Renaissance Revival house with wonderful stonework on the outside. A great part of the jewel lies inside. The rooms are panelled in this high Victorian exotic wood which is spectacular,” said Dinu Bumbaru of Heritage Montreal.

The property is being transformed into a high-end 12-storey hotel, but in the process, cracks have appeared in the stone facade, and it is visibly sagging to one side.

The Ville-Marie borough issued a notice requesting an engineering report on Jan. 21, when one of their inspectors discovered the danger.

“Stabilization measures have been put in place according to the engineering firm guidelines and following this the firm confirmed that there's no immediate danger of the facade collapsing,” said Anik de Repentigny, a spokesperson for the borough.

Quebec's Ministry of Culture and Communications is suing the owners, but would not discuss the case.

Tidan, which bought the Mount Stephen Club in 2006, and also owns many other downtown buildings and hotels, were not available for comment.

The building is classified as a provincial heritage building as well as a National Historic Site of Canada. It's considered to be one of the most important houses in the country.

It's not just the facade that's an issue. Bombaru said cracks could affect the humidity inside, which is a danger for the rare wood.

“We're surprised that this occurs in 2015/16, because we now have a lot of knowledge. We have great engineering expertise,” he said.

Heritage Montreal will suggest putting together an expert panel to help fix the landmark building.

“This is not St. Peters of Rome, but for Montreal and for Canada and Quebec, it's a very important building,” he said.