Eight fire engines and around 60 firefighters tackled a house fire on Rosendale Road in West Dulwich.
The whole of the loft conversion was destroyed by the blaze.
Station Commander Neil Guyett, who was at the scene said:
“This was a severe fire in the roof space of a three storey house. Thankfully there was no one in the property at the time of the fire. Firefighters worked hard to prevent the fire from spreading to surrounding properties.
“There was a lot of smoke in the local area and we asked nearby residents to keep their doors and windows closed.”
The Brigade was called at 0152 and the fire was under control by 0453. Fire crews from West Norwood, Brixton, Forest Hill, Norbury, New Malden and Peckham fire stations were at the scene. The cause of the fire is under investigation.