Four fire engines and around 25 firefighters were called to a fire at a house on Abbey View in Mill Hill.
Half of a rear extension at a detached house was damaged by the fire and plastic roofing on a side extension at a neighbouring property was also damaged. There were no reports of any injuries.
The Brigade was called at 1509 and the fire was under control by 1643. Fire crews from Mill Hill, Hendon and Stanmore fire stations were at the scene.
The cause of the fire is under investigation.