A townhouse in the United States is a single-family residence that must have at least two stories and share a wall with another house. Each townhouse, unlike a four-plex or duplex, is separately owned. However, the occupants of each townhouse share common areas including porches, patios, and garages. There are several types of townhouses, depending on how the separate units are arranged. If there is a private entrance for each unit, they are called "forks". If they share a private entrance, it is one door for all residents; this is called a "flock". In addition, some towns impose additional requirements on townhouse owners; for example, some require property taxes to be paid independently or limit what can be done to the property without first getting approval from the community. The legal definition of a townhouse varies from state to state but generally includes any house built before 1995 that has only one owner who lives there full time. Before you sell your house, make sure you know the rules by which it's governed to avoid trouble later. The number of floors required for a townhouse depends on the city or county where it is located. Some cities or counties may have building codes that require certain numbers of floors for certain types of buildings.