Four fire engines and around 25 firefighters were called to a flat fire on North Birkbeck Road in Leytonstone.
Most of a three-roomed basement flat in a converted semi-detached house was damaged by fire. One woman was treated on scene by London Ambulance Service crews.
The Brigade's 999 Control Officers took 13 calls to the blaze.
The Brigade was called at 0719 and the fire was under control by 0836. Fire crews from Leytonstone, Leyton, Stratford and Homerton fire stations attended the scene.
The fire is believed to have been accidental, but the exact cause has been recorded as undetermined.