Four fire engines and around 25 firefighters tackled a fire at a terraced building made up of shops with dwellings above on Broadway in West Ealing.
Most of a two bedroom flat within the mansard roof was damaged by the fire. There are no reports of any injuries.
Control Officers took the first of two calls at 1458 and mobilised crews from Ealing, Southall, Chiswick and Heston fire stations to the scene. The fire was extinguished by 1618.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.