Four fire engines and around 20 firefighters and officers were called to a fire at a shop with flats above in Woodhouse Road in North Finchley.
Part of the external ducting from first to second floor level was damaged by fire. Part of the roof was also damaged in the blaze.
The Brigade was called at 1632 and the fire was under control at 1713. Fire crews from Finchley, Southgate and Hornsey fire stations attended the scene.
The cause of the fire is under investigation.