Section 1906 provides prescriptive requirements for concrete foundation walls. Wall thickness depends on backfill height and soil bearing capacity. Typical 8-inch walls are used for up to 6 feet of backfill with normal soil pressure. Vertical reinforcement (rebar) is required with spacing typically 24 inches on center. Horizontal reinforcement is also required, with #4 bars spaced 18-24 inches vertically. Bond beams at the top of foundation walls distribute loads from walls above. Stem walls (walls above footings) require adequate reinforcement for bending stresses.