An application for the remodeling or alteration of an existing building for the purpose of increasing the number of dwelling units therein shall be accompanied by a plan in conformity with the requirements of an application for new multi-family dwelling or apartment buildings in the city. The plan shall show in detail the existing structure, including the electrical wiring system, the plumbing and heating facilities, the width of walls and foundations and the size of and location of joists and supporting beams. A plan shall also be submitted at the time of application showing the building in its entirety in detail as it is proposed to be remodeled or altered. The Director of Public Works shall keep a permanent record of the plans.