Changes to existing wiring of a building being modernized are considered and the code requirements for the upgraded facilities are presented. Various field survey techniques are described in order to determine what components can be reused or must be replaced. Several problems of electrical retrofit work are discussed from the points of local, state and national codes compliance, extent of demolition, replacement and refurbishing. The problems and the solutions to rehabilitation work are looked upon keeping in mind the cost of construction, while viewing alternate design approaches.