Four fire engines and around 25 firefighters were called to a house fire on Elaine Grove in Kentish Town.
Half of the roof of a mid-terraced house was damaged by fire. There were no reports of any injuries.
A London Fire Brigade spokesperson said: “There were smoke alarms fitted in the property, but they did not operate.
“Smoke alarms give the earliest possible warning when a fire starts. We encourage everyone to have smoke alarms fitted in every room where a fire could start, plus a heat alarm in the kitchen. It's important to test them regularly.”
The Brigade was called at 1526 and the fire was under control by 1802. Fire crews from Kentish Town, Holloway and Soho fire stations attended the scene.
The fire is believed to have been accidental and caused by hot works.