The newly-built rised patio at Pêle-Mêle in the city's Hull sector violated city by-laws because a fire hydrant sat in the middle, just popping above the patio's surface.
Fire hydrants must have a 1.5-metre radius of free space around them to ensure access to firefighters. This hydrant had wood surrounding it just inches away.
Gatineau city officials told CBC News the bar's owner never asked permission to build around the hydrant.
On Sunday, the bar acted in response by taking apart the patio. City officials said they would continue to investigate.