Six fire engines and around 40 firefighters tackled a fire on Woodmansterne Road in Carshalton.
Most of the first floor of a two-storey detached house was damaged by fire. There were no reports of any injuries.
The Brigade's 999 Control Officers received five calls about the fire.
The Brigade was called at 1714 and the fire was brought under control by 1824. Crews from Wallington, Sutton, Purley, Mitcham, Croydon and Forest Hill fire stations attended the scene.
The fire has been recorded as accidental.