Six fire engines and around 40 firefighters tackled a fire in a house in High Worple, Harrow.
The first floor of the semi-detached property was destroyed by the blaze and a large amount of the ground floor was damaged. A small part of the roof of an adjoining property was also damaged.
The Brigade was called at 1953 and the fire was under control by 2149.
Fire crews from Harrow, Northolt, Wembley and Stanmore Stations attended the blaze.
The cause of the fire is under investigation.