San Francisco Building Inspection Commission Codes § 3203.2

3203.2.1 Sidewalk trapdoor. Every basement extending under the sidewalk shall have an approved sidewalk trapdoor. The minimum size of the trapdoor opening shall be 4 feet by 4 feet (1.219 m by 1.219 m). However, trapdoors shall not be required where the basement is provided with an automatic sprinkler system. 3203.2.2 Sidewalk elevators. All openings hereafter constructed in sidewalks for sidewalk elevators shall be located in the outer half of the sidewalks, next to the curb. The outer edges of the openings shall be not more than 30 inches (762 mm) from the outer line of the curb. The length of the sides of the openings at right angles to the curb shall not exceed one-half of the width of the sidewalk and in no case shall it exceed 5 feet (1.524 m).

3203.2.3 Any other purpose. Openings on the sidewalks for any other purpose, if placed outside the property line, shall be covered with approved gratings having a maximum opening between bars of ½ inch (12.7 mm), or with covers having a rough surface, and rabbeted flush with the sidewalk. When a cover is placed in any sidewalk, it shall be placed as near as practicable to the line of the curb. All spaces under sidewalks shall be thoroughly ventilated. 3203.2.4 Framing. All framing supporting only the sidewalk opening shall be of noncombustible material. 3203.2.5 Guards. Metal guards will be required for openings in sidewalks in accordance with the Police Code. 3203.3 Electrical Transformers. No portion of any electrical transformer pad shall be constructed, nor electrical transformer installed on the surface of any portion of any public sidewalk.