1975 BOCA unchanged from 1972 BOCA. I don't have anything earlier.
SECTION 616.0 INTERIOR EXITWAY STAIRWAYS
616.1 Capacity: The capacity of stairways and doors per unit of exit
width shall be computed in accordance with Section 608.0. .
616.2 Minimum dimensions
616.2.1 Width: All interior exit way stairways shall be not less than
forty-four (44) inches in width, except that such width may be reduced
to thirty-six (36) inches in buildings of single exit construction when permitted by Section 609.3.
616.2.2 Headroom: The minimum headroom in all parts of the stair
enclosure shall be not less than SIX and two-thirds (6-2/3) feet.
616.2.3 Restrictions: stairways shall not reduce in width in the direction of exit travel.
616.3 Landings and platforms
616.3.1 Width: The least .dimension of landings and platforms shall be
not less than the width of stairway.
616.3.2 Vertical rise: In buildings of use group A (assembly) and use
group I (institutional) occupancy, the height of vertical rise shall not
exceed nine (9) feet between landings and intermediate platforms. In all
other buildings, a stairway shall not have a height of rise of more than
twelve (12) feet between landings.
616.4 Treads and risen
616.4.1 Minimum dimensions: The height of risers and width of treads
in inches shall be as indicated m the following Table 616.
Table 616
TREAD AND RISER SIZE
==============~~ ===~~~====~======
Use group Maximum riser Minimum tread*
Assembly and institutional 7-1/2" 10"
All others ~ 8" 9"
*All treads shall have a nosing or effective projection of 1". There shall not be a variation exceeding 3/16" in the height of risers.
616.4.2 Winders: Winders shall not be permitted in required exitway stairs, except that in one- and two-family dwellings and in ornamental stairways not required as an element of an exitway, treads with a minimum width of four (4) inches and an average width of nine (9) inches may be permitted.
