Four fire engines and around 25 firefighters were called to building under construction on Bellenden Road in Peckham.
A small part of the roof was damaged by the blaze.
The Brigade was called at 1039 and the fire was under control by 1134. Fire crews from Peckham, New Cross, Old Kent Road and Brixton fire stations attended the incident.
The cause of the fire is believed to be due to hot works being carried out on the roof.