| Primary value | 300 mm dia (G+1 to G+3) (G+5 → 400 mm · G+10 → 500–600 mm) |
| Applies to | Cast-in-situ bored piles · Buildings on weak alluvium, soft clay, or filled ground · Sites where raft would be uneconomical |
| Exceptions | G+1 to G+3 → 300 mm dia |
| G+4 to G+6 → 400 mm dia | |
| G+7 to G+10 → 500 mm dia | |
| G+11 to G+20 → 600–750 mm dia | |
| Tall building (G+20+) → 800–1200 mm dia or barrettes | |
| Pile L/D ratio (slenderness) → Keep ≤ 50 | |
| Measured as | Diameter of the bored shaft. Capacity scales roughly with diameter² for friction piles and with cross-section for end-bearing. Pile cap thickness should be at least 1.5× pile diameter. |
| Source | IS 2911 (Part 1, Sec 2) — Clause 5 📚 Cross-referenced |
3 related items across IS codes, knowledge articles, design rules, maps and tools
Pile diameter is the first design choice — it sets the rig you need on site, the spoil volume, and the load each pile can take. The 300/400/500/600 mm progression maps to commonly available rotary rigs in India and avoids one-off mobilisation surcharges.
300 mm bored piles are by far the most common in residential India — they're installed by tripod rigs that fit in narrow plots and don't need crane access. Anything 600 mm+ needs a track-mounted rotary, which reshapes site planning. Always confirm capacity with a pile load test before mass installation.