The stair stringer bears onto a thickened concrete slab footing with a minimum three-sixteenths-inch plate at the end and bearing connection, accommodating interstory drift. Stair stringers and concrete-filled pan treads are provided by the stair manufacturer using either HSS12x2x3/16 minimum or C12x20.7 minimum shapes, with flat plate stringers prohibited. The thickened slab footing extends a minimum of one foot six inches beyond the stair on each side and incorporates number four reinforcing bars top and bottom at eighteen inches minimum spacing.
STAIR STRINGERS BY STAIR MFR. SEE ARCH FOR SHAPE & CONFIG HSS12x2x3/16 MIN OR C12x20.7 MIN; NO FLAT PL STRINGERS PERMITTED THICKENED SLAB FTG; EXTEND 1'-6" MIN BEYOND STAIR, EACH SIDE SLAB ON GRADE PL3/16 MIN @ END AND BRG CONN BY STAIR MFR* CONCRETE FILLED PAN TREADS BY STAIR MFR; 2" MIN NOTE: * CONNECTION TO ACCOMMODATE INTERSTORY DRIFT #4 T&B 18" MIN 12" MIN
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