Strip Footing

A strip footing (also called continuous footing or wall footing) is a long narrow footing supporting a continuous load-bearing wall. Width is typically 2-5× the wall thickness; depth depends on bearing pressure and soil conditions. Used for traditional load-bearing masonry construction, perimeter walls of small houses, garden walls, and short walls of unit-level buildings. Indian Standard IS 1904:1986 governs strip footing geometry; IS 456:2000 covers RCC structural design; IS 1905:1987 covers masonry walls.

For a typical residential masonry wall (230 mm thick brick wall, single-storey load): bearing pressure check sized footing at 600-800 mm width with 200-300 mm depth. The wall load = wall self-weight (0.230 × 1.0 × 19 = 4.4 kN/m run) + roof load (typically 4-6 kN/m run for a small house) = 8-10 kN/m run. With SBC = 150 kN/m²: required width = 10/150 = 67 mm — far less than the 600 mm minimum, so geometric / construction concerns govern, not bearing pressure. For multi-storey load-bearing walls (3+ storeys), the wall load reaches 30-50 kN/m run, and bearing-pressure-driven sizing becomes governing.

Design considerations: (a) Plain (unreinforced) PCC footings can carry small wall loads (≤ 15 kN/m on M10 PCC, depth ≥ 0.5× projected width); for larger loads, RCC reinforcement is required to span horizontally across the projection; (b) Soil bearing pressure check at full wall load; (c) Settlement — strip footings are more prone to differential settlement along the length, especially across non-uniform soil — IS 1904 allows up to 1/300 of length differential without distress; (d) Drainage — water accumulating along the footing length causes long-term settlement and reduced bearing capacity. Common Indian construction issue: strip footings cast in monsoon-saturated soil without proper dewatering; the footing carries diluted concrete and reduces in-situ strength by 20-40%.