Section 28. Except as provided in section thirty with respect to projects leased from the federal government, every housing project shall be subject to all laws and all ordinances, by‐laws and regulations of the city or town in which it lies, relating to the construction and repair of buildings, town planning, zoning and the protection of the public health; provided, that with the approval of the department and the division of professional licensure, any building in a housing project of not more than three stories in height which is divided into two or more sections by fire division separations in accordance with any special law relative thereto or with any ordinance, by-law or regulation of the city or town in which it lies, which contains an enclosed stairway in each section extending from the roof to the ground directly accessible to the occupants of each dwelling unit therein, which is built of fireproof or fire resistive construction as defined by any special law relative thereto or by any ordinance, by‐law or regulation of the city or town in which it lies, and which, together with the other buildings on the same project, does not occupy more than thirty per centum of the area thereof, may be designed, erected and maintained with only one means of egress from a dwelling unit to a stairway or public corridor; provided, that when any room in a dwelling unit is more than forty feet from such means of egress, there shall be two egresses from such dwelling unit located at points as widely separated from one another as may be reasonably feasible, with not more than four dwelling units above the second story in each section, with exterior egress doors not less than three feet in width, although such dwelling units contained in the aggregate more than eight rooms and the only means of egress is as above described; and provided, further, with the approval of the department, and the division of professional licensure, any building in a housing project or any section of such a building which is set apart by a fire wall or fire walls of more than three stories in height, which is of fireproof or fire resistive construction in accordance with any special law relative thereto, or with any ordinance, by‐law or regulation of the city or town in which it lies, and which is provided with two enclosed stairways isolated from each other by fire division separations in accordance with any special law relative thereto or with any ordinance, by‐law or regulation of the city or town in which it lies, or as widely separated from each other as may be reasonably feasible, and which, if of more than six stories in height, is equipped with automatic sprinklers installed in cellars, basements, workrooms, shops, storerooms and kitchens, may be designed, erected and maintained with only one means of egress from each dwelling unit to a public corridor; provided, that when any room of a dwelling unit is more than forty feet from such means of egress, there shall be two egresses from such dwelling unit located at points as widely separated from one another as may be reasonably feasible; and provided, further, that in buildings three or more stories in height, stairs and landings, and doors connecting public corridors and stair enclosures, when serving not more than three hundred persons, shall be not less than three feet in width between walls or between wall and balustrades with stairs equipped with a handrail on one side, although the only means of egress and fire extinguishing apparatus are as above described.