For inspectors especially those that perform new construction phase inspections it’s somewhat confusing in the building codes if the tables for concrete wall reinforcement apply or if engineering design is required. In the first graphic the full height 8’ basement wall, if it has more than 4 foot of unbalanced fill has to be restrained. To be restrained the sub-floor (joists and plywood) have to be in place prior to back-fill to resist inward movement at the top of the wall. The 6’ and 4’ step down wall sections are not restrained at the top, which requires special design if they retain more that 4’ of unbalanced fill, have a surcharge or retains hydrostatic water pressure. See the second graphic for showing surcharges like sloped soil or a live load surcharge like a vehicle and hydrostatic water pressure. In the first graphic the 6’ basement wall section retains more than 4’ of unbalanced fill, which requires an engineered design as a cantilevered retaining wall. The 4’ basement wall section would not require and engineered design unless there was a surcharge or hydrostatic pressure.
NOTE: Only the surcharge within the 45 degree dashed line is considered in the wall design.
I have attached actual photos of a step-down foundation with a soil surcharge that pushed the top of the foundation wall in cracking the basement floor along the edge of the footing. This wall was retaining some soil surcharge and hydrostatic pressure. The water drains along the foundation saturating the soil. The backfill soil was inorganic clay that will swell when wet, which is not recommended for any basement wall.