The roof of the house on Bashurst Hill in Itchingfield was spotted alight at 00:30 BST.
West Sussex Fire & Rescue sent four engines to fight the blaze and all occupants were accounted for.
Sussex Police said the cause of the blaze was unknown but there was nothing to suggest it was deliberate.
One person has been taken to hospital after a serious fire gutted a house in West Sussex during the early hours on Saturday.