The fire began on the roof of an unoccupied portion of the Jardinsde la Côte seniors residence in Beaupré, about 40 kilometres east of Quebec City.
Firefighters got the call around 10:45 a.m. ET and quickly got the blaze under control.
The occupied portion of the residence was evacuated as a precaution. No injuries were reported.
"Given the circumstances, it went very well," said Mayor Michel Paré.
Between 150 and 185 people live in the independent-living retirement home.
"They've been moved to a phase [of the home] the furthest away from the one that caught fire," Paré said.
Construction on the now-damaged Phase 3 of the retirement home began in Oct. 2013 and was supposed to open in March 2014.
On the Jardins de la Côte website, it says the new portion is supposed to house 28 independent-living apartments and 42 rooms for people with loss of autonomy.