N.Y. Multiple Dwelling Law § 50

§ 50. Entrance halls. Every entrance hall in every multiple dwelling\nerected after April eighteenth, nineteen hundred twenty-nine, shall be\nat least four feet in clear width from the entrance to the first stair,\nand beyond that shall be at least three feet eight inches in clear\nwidth. If such an entrance hall is the only entrance to more than one\nflight of stairs, the required width of such hall shall be increased in\nevery part, for each such additional flight of stairs, by one-half the\nwidth required for one flight of stairs.\n