Section 269 - Application of provisions1. The provisions of sections two hundred and sixty-one, two hundred and sixty-two, two hundred and sixty-three, two hundred and sixty-five, two hundred and sixty-six, and two hundred and sixty-seven shall apply to all buildings erected after October first, nineteen hundred and thirteen, and to all construction made after that date in buildings erected prior to that date. The board shall adopt rules affecting construction made before October first, nineteen hundred and thirteen, in buildings theretofore erected, requiring compliance with such of the requirements of said sections, or with such other or different requirements as it finds reasonable and adequate to protect persons employed in such buildings against fire.2. Altered buildings. When changes are made to a building erected prior to October first, nineteen hundred thirteen, which are so material and extensive as to constitute a new building, such building shall comply with the provisions of section two hundred seventy. However, the words material or extensive shall not apply if the structure is altered by adding an extension horizontally in such manner as to increase any or all of its floor areas by not more than twenty-five per centum.