Eight fire engines and around 60 firefighters were called to a fire at a derelict church hall on Addison Avenue in Southgate.
The roof of the building was destroyed. There were no reports of any injuries.
Station Commander Will Thompson who was at the scene said: "The fire produced smoke that affected the local area, and residents nearby were advised to keep their windows and doors closed where possible.
"One of the Brigade's 32-metre turntable ladders was deployed as a water tower, allowing crews to tackle the flames from above."
The Brigade's Control Officers took the first of nearly 50 calls to the fire at 1840 and sent crews from Southgate, Barnet, Tottenham, Edmonton, Finchley and surrounding fire stations to the scene. The fire was under control by 2207.
The cause of the fire is under investigation.