Four fire engines and around 25 firefighters were called to a fire on York Road in Ilford.
A single-storey timber outhouse was destroyed by the fire and part of a three-roomed flat on the ground floor of a two-storey building was also damaged. One adult and two children left the building before the Brigade arrived. They were assessed on scene by London Ambulance Service crews but there were no reports of any injuries.
The Brigade's 999 Control Officers took 21 calls to the fire.
The Brigade was called at 1340 and the fire was under control by 1510. Fire crews from Barking, East Ham, Leytonstone and Dagenham were at the scene.
The cause of the fire is under investigation.