Six fire engines and 35 firefighters and officers were called to a fire at a house in Westbourne Road in Feltham.
The ground and first floors of the property were destroyed by fire. A small part of the fascia and guttering to an adjoining property were damaged by fire.
Two adults and two children left the property before the arrival of the Brigade. One woman was treated at the scene by firefighters for smoke inhalation.
The Brigade was called at 1630 and the fire was under control at 1919. Fire crews from Feltham, Twickenham and Heston fire stations attended the scene.
The cause of the fire is believed to be accidental and due to a failure in an electrical consumer unit.