Four fire engines and around 25 firefighters were called to a fire at a house converted into flats on Salisbury Road in Barnet.
Part of a flat on the first floor and part of the loft conversion and roof were damaged by fire. There were no reports of any injuries.
Alston Road was closed whilst firefighters worked to make the scene safe.
The Brigade was called at 1244 and the fire was under control by 1359. Fire crews from Mill Hill, Southgate, Barnet and Finchley fire stations attended the scene.
The fire is believed to have been caused by hot works being carried out.