A building should be regarded as residential building when more than half of the floor area is used for dwelling purposes. Other buildings should be regarded as non-residential. Two types of residential buildings can be distinguished: - houses (ground-oriented residential buildings): comprising all types of houses (detached, semi- detached, terraced houses, houses built in a row, etc.) each dwelling of which has its own entrance directly from the ground surface; - other residential buildings: comprising all residential buildings other than ground-oriented residential buildings as defined above.