(1)
The clear height over stairs shall be measured vertically, over the clear width of the stair, from a straight line tangent to the tread and landing nosings to the lowest point above. (See Note A-3.4.3.4.)
(2)
Except as provided in Sentences (3) and (4) and Article 9.8.4.7., the clear height over stairs shall not be less than 2 050 mm.
(3)
Except as provided in Article 9.8.4.7., the clear height over stairs serving a single dwelling unit or a house with a secondary suite including their common spaces shall not be less than 1 950 mm.
(4)
The clear height over stairs that are located under beams and ducting in secondary suites shall not be less than 1 850 mm.