Six fire engines and around 40 firefighters were called to a fire at a house on Albury Drive in Pinner.
Part of the ground floor, first floor and roof of a detached house were damaged by the fire. A single storey wooden shed in the rear of the property was destroyed by the fire and a small part of an adjacent detached property was also damaged.
Firefighters cooled a propane cylinder to an ambient temperature and removed it, as cylinders can explode when exposed to heat.
One woman left the property before the Brigade arrived. She was treated for smoke inhalation at the scene by London Ambulance Service crews.
The Brigade was called at 1440 and the fire was under control by 1635. Fire crews from Ruislip, Northolt, Stanmore, Hillingdon and Southall fire stations attended the scene.
The cause of the fire is under investigation.