Six fire engines and around 40 firefighters attended a fire on Playgreen Way in Bellingham.
The roof of an end-of-terraced house was destroyed by fire, along with half of the first floor and part of the ground floor. Half of the property's garden was also alight. The loft of an adjoining house was also partially damaged by fire.
Several people left the properties before firefighters arrived and were assessed at the scene by London Ambulance Service.
One gas cylinder was removed from the scene and cooled it to an ambient temperature as a precaution, as some cylinders can explode when exposed to heat.
The Brigade received the first of 11 calls at 0655 and Control Officers mobilised crews from Forest Hill, Lewisham, Beckenham, Bromley, Greenwich and Lee Green fire stations to the scene. A 32-metre turntable ladder from Forest Hill Fire Station also attended and was deployed as a water tower to help extinguish the fire from above.
The fire was extinguished by 0907.
The cause of the fire is under investigation.