Four fire engines and around 25 firefighters were called to a fire at a house on Meadway in Barnet.
The ground floor of a semi-detached house was destroyed by the fire and part of the first floor was also damaged.
A man and woman left the property before the Brigade arrived. They were both suffering smoke inhalation and the man was treated on scene by London Ambulance Service crews and the woman was taken to hospital.
The Brigade was called at 1828 and the fire was under control by 2014. Fire crews from Barnet and Finchley fire stations attended the scene as well as one fire engine from Hertfordshire Fire and Rescue Service.
The cause of the fire is under investigation.