Four fire engines and around 25 firefighters were called to a fire at a shop on Stanhope Road in North Finchley.
A domestic extractor fan in the roof void was destroyed by fire. There were no reports of any injuries.
The Brigade was called at 1828 and the fire was under control by 1948. Fire crews from Finchley, Barnet and Hendon fire stations attended the scene.
The cause of the fire is under investigation.