One child and two adults were taken to hospital suffering from smoke inhalation after being rescued at the house on Marlborough Road.
Fire crews were called to the blaze at 4.55am on Saturday and had brought it under control by 6.16pm.
Firefighters rescued three people from the loft conversion. A woman from the adjacent property was also treated at the scene for smoke inhalation by paramedics.
Three others escaped from the property before the fire brigade arrived.
A pile of rubbish in the front garden was entirely destroyed by the fire, which also damaged part of the ground floor of the house.
Four fire engines, and 21 firefighters and officers, from Plaistow, East Ham, Stratford and Leytonstone fire dealt with the fire.
The cause is under investigation by fire officers and the police.
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