If the crack is noticeably deeper than the plaster or paint, that could also be problematic, as could cracks close to windows or doors, or spanning form where the wall meets the ceiling.

Montreal Metro's Green line is closed between Lionel-Groulx and Frontenac stations for an indefinite period, after a water leak led engineers to detect cracks in the vaulted ceiling between Berri ...

The Montreal Metro's Green Line is up and running Tuesday morning, a day after engineers uncovered cracks in the tunnel's vaulted ceiling, according to Montreal's transit authority.