Ten fire engines and 72 firefighters and officers were called to a fire at a hotel under construction on Uxbridge Road in Ealing this morning.
The Brigade's 999 control officers took around 40 calls about the visible blaze.
The whole of the roof of the eight storey building was alight and part of the plant room. There were no reports of any injuries.
The Brigade was called at 1130 and the fire was under control at 1325. Fire crews from Ealing, Acton, Southall, Chiswick, Park Royal, Wembley and other surrounding fire stations attended the scene.
The cause of the fire is believed to be accidental and due to the unsafe disposal of smoking materials.