§ 269. Application of provisions. 1. 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.