(1) Exterior concrete stairs with more than two risers and two treads shall be,
(a) supported on unit masonry or concrete walls or piers not less than 150 mm in cross-section, or
(b) cantilevered from the main foundation wall.
(2) Stairs described in Sentence (1), when cantilevered from the foundation wall, shall be constructed and installed in conformance with Subsection 9.8.10.
(3) The depth below ground level for foundations for exterior steps shall conform to the requirements in Section 9.12.