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California Building Code Excerpt

Section 11B-504 Stairways

Code excerpt regarding technical requirements for stairways: general, treads and risers, open risers, tread surface, nosings, and handrails.

11B-504 Stairways

11B-504.1 General. Stairs shall comply with Section 11B-504.

11B-504.2 Treads and risers. All steps on a flight of stairs shall have uniform riser heights and uniform tread depths. Risers shall be 4 inches (102 mm) high minimum and 7 inches (178 mm) high maximum. Treads shall be 11 inches (279 mm) deep minimum.

Exception: Curved stairways with winder treads are permitted at stairs which are not part of a required means of egress.

11B-504.3 Open risers. Open risers are not permitted.

Exceptions:

  1. On exterior stairways, an opening of not more than 1/2 inch (12.7 mm) may be permitted between the base of the riser and the tread.
  2. On exterior stairways, risers constructed of grating containing openings of not more than 1/2 inch (12.7 mm) may be permitted.

11B-504.4 Tread surface. Stair treads shall comply with Section 11B-302. Changes in level are not permitted.

Exception: Treads shall be permitted to have a slope not steeper than 1:48.

11B-504.4.1 Contrasting stripe. Interior stairs shall have the upper approach and lower tread marked by a stripe providing clear visual contrast. Exterior stairs shall have the upper approach and all treads marked by a stripe providing clear visual contrast.

The stripe shall be a minimum of 2 inches (51 mm) wide to a maximum of 4 inches (102 mm) wide placed parallel to, and not more than 1 inch (25 mm) from, the nose of the step or upper approach. The stripe shall extend the full width of the step or upper approach and shall be of material that is at least as slip resistant as the other treads of the stair. A painted stripe shall be acceptable. Grooves shall not be used to satisfy this requirement.

Advisory 11B-504.4.1 Contrasting stripe. Some designers propose to provide a group of tooled grooves in lieu of the contrasting color. While grooves do provide shadow lines in some lighting conditions, these shadows cannot be relied upon under all lighting conditions. In addition, the spaces between the grooves do not provide any contrast.

11B-504.5 Nosings. The radius of curvature at the leading edge of the tread shall be 1/2 inch (12.7 mm) maximum. Nosings that project beyond risers shall have the underside of the leading edge curved or beveled. Risers shall be permitted to slope under the tread at an angle of 30 degrees maximum from vertical. The permitted projection of the nosing shall extend 1 1/4 inches (32 mm) maximum over the tread below.

Exception: In existing buildings there is no requirement to retroactively alter existing nosing projections of 1 1/2 inches (38 mm) which were constructed in compliance with the building code in effect at the time of original construction.

Advisory 11B-504.5 Nosings. While Chapter 10 may allow larger radius of curvature at the leading edge (nosing) of the tread, this radius must be no larger than 1/2 inch to comply with both Chapter 10 and Chapter 11B requirements.  Additionally, because it is possible to catch the top of one’s shoe on the underside of stair nosings, access compliance regulations require the underside of nosings to be free of abrupt changes—a beveled slope or non-square underside.

Figure 11B-504.5 Stair Nosings
Figure 11B-504.5 Stair Nosings

11B-504.6 Handrails. Stairs shall have handrails complying with Section 11B-505.

11B-504.7 Wet conditions. Stair treads and landings subject to wet conditions shall be designed to prevent the accumulation of water.

11B-504.8 Floor identification. Floor identification signs required by Chapter 10, Section 1023.9 complying with Sections 11B-703.1, 11B-703.2, 11B-703.3 and 11B-703.5 shall be located at the landing of each floor level, placed adjacent to the door on the latch side, in all enclosed stairways in buildings two or more stories in height to identify the floor level. At the exit discharge level, the sign shall include a raised five pointed star located to the left of the identifying floor level. The outside diameter of the star shall be the same as the height of the raised characters.

Relevant excerpt from Section 1023.9:

In addition to the stairway identification sign, raised characters and braille floor identification signs that comply with Chapter 11B shall be located at the landing of each floor level, placed adjacent to the door on the latch side, in all enclosed stairways in buildings two or more stories in height to identify the floor level. At the exit discharge level, the sign shall include a raised five pointed star located to the left of the identifying floor level. The outside diameter of the star shall be the same as the height of the raised characters.

Because the floor identification sign is a tactile sign, it is reasonable to assume the placement “adjacent to the door on the latch side” required here is still subject to the expanded tactile sign placement rules at Section 11B-703.4.2.