Four fire engines and around 25 firefighters were called to a fire at a bungalow in The Crescent, Harrow.
Half of the bungalow was damaged by the fire and the roof of the property was destroyed. One man and one woman were treated at the scene by London Ambulance Service crews.
A man and a woman left the property before the Brigade arrived. They were suffering from smoke inhalation and were treated at the scene by London Ambulance Service crews.
The Brigade was called at 1531 and the fire was under control by 1726. Fire crews from Harrow, Northolt and Wembley fire stations were at the scene.
The cause of the fire is believed to be accidental and due to hot works being carried out as part of a refurbishment.