Four fire engines and around 25 firefighters tackled a fire on Trinity Road in Southall.
A ground floor single-storey extension at a mid-terraced house was destroyed by fire. There were no reports of any injuries.
The Brigade's 999 Control Officers received six calls about the fire.
The Brigade was called at 1120 and the incident was over for firefighters by 1214. Crews from Southall, Ealing, Hayes and Heston fire stations attended the scene.
The fire is believed to have been caused by an electrical fault in an extension lead.