(1)
Every stairway shall be lighted.
(2)
Except as provided in Sentence (3), 3-way wall switches located at the head and foot of every stairway shall be provided to control at least one lighting outlet with fixture for stairways with 4 or more risers in dwelling units and houses with a secondary suite including their common spaces.
(3)
The stairway lighting for basements that do not contain finished space or lead to an outside entrance or built-in garage and which serve not more than one dwelling unit is permitted to be controlled by a single switch located at the head of the stairs.