Eight fire engines and around 60 firefighters were called to a fire at a shop with flats above on Westow Hill in Crystal Palace.
Most of the ground floor shop was damaged by the fire. Part of the first floor and part of the roof were also damaged as well as the roof of an adjoining property. One man left the building before the Brigade arrived and was treated for smoke inhalation on scene by London Ambulance Service crews.
Station Commander Graeme Hunter, who was at the scene, said: "Crews were faced with heavy smoke issuing from the building when they arrived, which had prompted a high number of calls to our Control Officers.
"Firefighters worked hard to bring the blaze under control. It had spread into the void between the ground and first floor so was a challenging fire to fight.
"We had an aerial ladder at the scene which assisted crews with tackling the blaze externally and supporting firefighters who fought the fire internally.
"There were local road closures in place so we advised motorists to avoid the area where possible as we were on scene for some time."
The Brigade's 999 Control Officers took eight calls to the blaze.
The Brigade was called at 1307 and the fire was under control by 1532. Fire crews from Lambeth, Brixton, Lewisham, Mitcham, Clapham, and surrounding fire stations were at the scene.
The Brigade's fire investigators believe the fire was caused by hot sparks from the grinding down of metal pins used during shoe repair entering a collection bin below containing combustible materials.