Six fire engines and around 40 firefighters were called to a fire at a disused house on Sanders Lane in Mill Hill.
The ground and first floors of an end-of-terrace house were destroyed by the fire and part of the roof was damaged. The roofs of another two adjoining terraces were also damaged. There were no reports of any injuries.
The Brigade was called at 1344 and the fire was under control by 1726. Fire crews from Hendon, Mill Hill, West Hampstead, Barnet and Hornsey fire stations were at the scene.
The cause of the fire has been recorded as undetermined.