Six fire engines and 35 firefighters and officers were called to a fire at a house in Glendale Avenue, Edgware.
The roof of a two-storey semi-detached house was destroyed and most of the first floor was damaged by the fire.
Two people left the property before the Brigade arrived and there were no reports of any injuries.
Station Manager Jon Holt, who was at the scene, said: "Crews worked extremely hard to stop the fire spreading and contain it to the n roof of the property."
The Brigade was called at 8.40pm on Monday evening and the fire was under control at just after 10pm . Fire crews from Mill Hill, Harrow, Hendon, Barnet and surrounding fire stations attended the scene.
The. cause of the fire is under investigation.