An elderly woman returned from a shopping trip to find more than 20 fire officers battling a blaze in her home on Tuesday (27).
The fire, which started around 1pm in Windsor Road, Harrow Weald, destroyed Carolina Bailey's loft and roof.
The 74-year-old was treated by paramedics for shock and was comforted by her son and neighbours.
Emmanuel Oshodi, 50, who lives next door with his wife and three children, helped kicked down the door believing Mrs Bailey was still in the house. The engineer said: "I ran next door and kicked down the door because I thought Carolina was in the house.
"There was a lot of smoke everywhere and lots of people had run outside to see what was going on.
"I broke down the door and ran upstairs. I couldn't see her so I had a quick look downstairs and ran back out. She had a lucky escape."
Dave Jones, watch manager at Harrow Fire Station, helped tackle the fire. He said: "We are still looking into the cause of the fire. We had a lot of calls from neighbours but when we arrived we still didn't know if anyone was in the house. We have made sure that the floors which have not been damaged are protected and an investigation will be carried out."