§ 14. Application of chapter to uncompleted dwellings. 1. The provisions of this chapter relating to multiple dwellings erected after April eighteenth, nineteen hundred twenty-nine, shall not apply to any multiple dwelling for which plans were on file with the department or a permit to commence building was issued by the department before August ninth, nineteen hundred twenty-nine, and the entire building shall have been completed according to the plans filed with the department, subject to any lawful subsequent amendment thereto, before July first, nineteen hundred forty-seven.

2. No provisions of any part of this section shall be deemed to prohibit the amendment of any plans filed and approved before April eighteenth, nineteen hundred twenty-nine, if such amendment would have been lawful before such date, or if such amendment complies with the requirements of this chapter for alterations to buildings of like class and kind existing before April eighteenth, nineteen hundred twenty-nine.

3. A permit to commence building issued by the department before April eighteenth, nineteen hundred twenty-nine, based upon plans filed and approved for a multiple dwelling described in subdivision one, shall be deemed to be in compliance with section three hundred.

4. The provisions of this chapter relating to multiple dwellings erected and occupied as such before April eighteenth, nineteen hundred twenty-nine, shall apply to the dwellings described in this section; except, however, that unless otherwise expressly required in article three nothing in this chapter shall be construed to require any change in the plans or occupancy of any such dwelling if it be fireproof and the plans therefore when filed were in compliance with the provisions of all local laws, ordinances, rules and regulations applicable thereto and in effect on April eighteenth, nineteen hundred twenty-nine, or were subsequently amended to comply with such provisions.