A vacant building is one that is unoccupied and in serious disrepair. A building that is unoccupied but in reasonably good repair would not be considered a vacant building.

There are 5,699 vacant buildings in the City of St. Louis.

According to the US Census Bureau, a building is vacant if no one was living in it at the time of the census interview, unless the occupants were temporarily absent. A vacant building may be one which is entirely occupied by persons who have a usual residence somewhere else.

Vacant buildings are a sign of neighborhood distress. Areas with large numbers of vacant and abandoned buildings can indicate to people that the neighborhood is not a fit place to live.

Vacant buildings can also be fire hazards. They are most dangerous to people who live next door to them. People can also lose their fire insurance if they live next door to a building that has been vacant for a long time.

Vacant buildings are often dangerous. Floors and/or walls can collapse when the building has not been maintained and allowed to deteriorate. They may often contain lead, asbestos, and other environmental hazards. Vacant buildings can also be fire hazards, especially when the gas has not been turned off. People can also lose their fire insurance if they live next door to a building that has been vacant for a long time.

It is often difficult to determine who owns a vacant building. The assessor's office has records of who the official owner is. However, the name listed may be a "straw party" or a front name for an individual who does not want to be identified. These owners are usually absentee landlords.