Four fire engines and around 25 firefighters were called to a fire at an outbuilding on New Heston Road in Hounslow.
More than half of a single-storey outbuilding at the rear of a property was damaged by the fire. There were no reports of any injuries.
The Brigade was called at 1704 and the fire was under control by 1821. Fire crews from Heston, Southall and Feltham fire stations attended the scene.
The cause of the fire is under investigation.