The fire was reported around 3:37 p.m. in a vacant Victorian-style duplex that was undergoing renovations.
About 80 firefighters responded, climbing on the roof and using hacksaws to cut holes allowing the flames to ventilate.
They reported knocking down the blaze at 4:06 p.m.
Firefighters said the 5,100 square-foot home was built in 1905.
No injuries were reported.
The cause of the fire is under investigation, although firefighters reported finding a broken natural gas line in the attic that fueled the flames.