Four fire engines and around 25 firefighters were called to a fire at a maisonette on Melfort Road in Thornton Heath.
Part of a split-level maisonette on the first and second floors of a converted mid-terraced house was damaged by the fire. Three adults and a child left the building before the Brigade arrived. There were no reports of any injuries.
The Brigade's 999 Control Officers took 13 calls to the blaze.
The Brigade was called at 0931 and the fire was under control by 1158. Fire crews from West Norwood and Croydon fire stations were at the scene.
The fire is believed to have been caused by an overloaded electrical supply which overheated.