Table 6.10 – Stairs
Current Guidelines:  
4.1.3  Accessible Buildings: New Construction.  Accessible buildings and facilities shall meet the following minimum requirements: . . . 

(4)  Interior and exterior stairs connecting levels that are not connected by an elevator, ramp, or other accessible means of vertical access shall comply with 4.9.

4.9.2  Treads and Risers.  On any given flight of stairs, all steps shall have uniform riser heights and uniform tread widths.  Stair treads shall be no less than 11 in (280 mm) wide, measured from riser to riser (see Fig. 18(a)).  . . .

Final Revised Guidelines:  
210.1 General.  Interior and exterior stairs that are part of a means of egress shall comply with 504.
Exceptions: . . .
2.  In alterations, stairs between levels that are connected by an accessible route shall not be required to comply with 504 except that handrails complying with 505 shall be provided when the stairs are altered. . . .

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 (100 mm) high minimum and 7 inches (180 mm) high maximum.  Treads shall be 11 inches (280 mm) deep minimum.

Model Codes & Standards
IBC 2000:  Sections 1003.3.3.3 and 1003.3.3.3.1 have equivalent requirements for stairs that are part of a means of egress.  

IBC 2003:  Sections 1009.3 and 1009.3.1 have equivalent requirements for stairs that are part of a means of egress. 

ICC/ANSI A117.1-1998:  Section 504.2 has equivalent requirements for treads and risers.