Six fire engines and around 40 firefighters tackled a fire at a house on Bowrons Avenue in Wembley.
A hot water cylinder was destroyed by the fire. Part of the first floor and most of the dormer extension were also damaged by the fire. There were no reports of any injuries.
Firefighters used one of the Brigade's 32-metre turntable ladders as an observation tower at the scene.
The Brigade was called at 1021 and the fire was under control by 1143. Firefighters from Wembley, Park Royal, Acton and surrounding fire stations attended the scene.
The fire is believed to have been accidental and caused by a fault in a hot water cylinder.