Eight fire engines and around 60 firefighters tackled a fire at a bungalow on Falcon Way in Harrow.
Most of the ground floor of a mid-terraced bungalow and half of the roof were damaged by fire. One man left the building before the Brigade arrived. Two people were treated on scene by London Ambulance Service crews.
The Brigade was called at 1711 and the fire was under control by 1829. Fire crews from Northolt, Stanmore, Hendon, Park Royal and surrounding fire stations attended the scene.
The cause of the fire is under investigation.