Four fire engines and around 25 firefighters were called to a fire on Roundtable Road in Bromley.
A tree house and a garden shed were destroyed by the fire and a summerhouse in the garden of a neighbouring property and some fence panels were damaged. There were no reports of any injuries.
The Brigade's 999 Control Officers took 17 calls to the fire.
The Brigade was called at 1430 and the fire was under control by 1605. Fire crews from Lewisham, Beckenham, Lee Green and Forest Hill fire stations were at the scene.
The Brigade's fire investigators believe the fire was caused by a heat lamp.