The maximum density of occupancy of any dwelling unit by persons shall not exceed either:
A. 
For the first occupant, 150 square feet of floor space and at least 100 square feet of floor space for every additional occupant thereof, the floor space to be calculated on the basis of total habitable room area; or
B. 
A total number of persons equal to two times the number of its habitable rooms.
Not more than one family, plus two occupants unrelated to the family, except for guests or domestic employees, shall occupy a dwelling unit.
The ceiling height of any habitable room shall be at least seven feet, except that in any habitable room under a sloping ceiling, at least 1/2 of the floor area shall have a ceiling height of at least seven feet, and the floor area of that part of such room where the ceiling height is less than five feet shall not be considered as part of the floor area in computing the total floor area of the room for the purpose of determining the maximum permissible occupancy.
No space located partially or totally below grade shall be used as a habitable room of a dwelling unit unless approved by the Secretary in writing and unless:
A. 
The floor and those portions of the walls below grade are of waterproof and dampproof construction.
B. 
The minimum window area is equal to at least that required in § 86-12, and such window area is located entirely above the grade of the ground adjoining such window area or, if windows are located wholly or partly below grade, there is constructed a properly drained window well whose open area is equal to or greater than the area of the masonry opening for the window, the bottom of the window well is below the top of the impervious masonry construction under this window and the minimum horizontal distance at a right angle from any point of the window well is equal to or greater than the vertical depth of the window well as measured from the bottom of the masonry opening for the window, except where there is supplied adequate artificial illumination.
C. 
The total openable window area in each room is equal to at least the minimum as required under § 86-13 of this chapter, except where some other approved devices affording adequate ventilation and humidity control are supplied.
D. 
There are no pipes, ducts or other obstructions which interfere with the normal use of the room or area.
In every dwelling unit of two or more rooms, every room occupied for sleeping purposes shall contain at least 70 square feet of floor space for the first occupant and at least 50 square feet of floor space for each additional occupant thereof.
No dwelling or dwelling unit containing two or more sleeping rooms shall have such room arrangements that access to a bathroom or water closet compartment intended for use by occupants of more than one sleeping room can be had only by going through another sleeping room; nor shall room arrangements be such that access to a sleeping room can be had only by going through another sleeping room or a bathroom or water closet compartment.
Every dwelling unit shall have at least four square feet of floor-to-ceiling height closet space for the personal effects of each permissible occupant; if it is lacking, in whole or in part, an amount of space equal in square footage to the deficiency shall be subtracted from the area of habitable room space used in determining permissible occupancy.