| Primary value | 1.0 to 1.5 m (below natural ground level) |
| Applies to | Isolated column footings on stable cohesive soil · G+1 to G+3 residential framing · Sites without seasonal water-table issues |
| Exceptions | Black cotton (BC) soil → 1.5–2.0 m below shrinkage zone |
| Filled-up / made-up ground → Down to undisturbed strata | |
| G+4 and above → 1.8–2.5 m | |
| IS 1904 minimum below GL → 1.0 m | |
| Measured as | Vertical distance from existing natural ground level to the underside of the footing PCC. Increase to clear seasonal moisture variation, frost line, or scour line near streams. |
| Source | IS 1904 — Clause 4.1, 4.2 ✓ Verified |
10 related items across IS codes, knowledge articles, design rules, maps and tools
Foundation depth has to clear the seasonal moisture-active zone (top 1.0–1.5 m in most Indian soils) and reach competent bearing strata. A 0.6 m footing on swelling BC soil heaves up to 100 mm in monsoon — visible as horizontal cracks in the plinth band — so 1.5 m is the absolute floor on shrinkage soils.
Most Indian residential builders default to 1.2 m depth on assumed-good soil without a soil test. On BC soil belt (Maharashtra, Gujarat, MP, Karnataka) responsible builders go to 1.8–2.0 m and add a sand cushion or under-reamed pile. Skipping the soil test is the #1 root cause of plinth-cracking complaints.