Housing Code SS1002 (b) defines a building to be inadequate if it lacks elevator service, as required by Section 713.1 of the code. This means that any portion of the building for which an elevator was not originally specified in the construction documents is considered unsafe. If an elevator becomes inadequate at any time after construction has been completed, the building is considered unsafe and must be brought up to code. An elevator can become inadequate for many different reasons. For example, if there is no electrical power to the car, then it cannot be operated. If its drive system fails, then it cannot be moved. If its walls are not strong enough to support itself over rough ground or if its roof collapses, then it is unfit for use. Buildings with elevators that do not function as required by law or city codes are known as "defective" or "unsafe." The people who live or work in these buildings are said to be "elevator users." When an elevator becomes inadequate, some people may need to be evacuated from their apartments or offices while work is done on making the elevator safe again. This is called "elevator remediation." Elevator remediation can be expensive.