General Steel Estimation
1. Steel requirement for RCC works (general):
For residential buildings, steel consumption ≈ 2.5–3.5% of concrete volume. For commercial/high-rise ≈ 4–5%. This helps in preliminary BOQ estimation.
2. Steel in RCC slab:
Slab requires ≈ 1% of concrete volume. Example: 1 m³ slab concrete = 78.5 kg steel (Fe415).
3. Steel in beams:
Beams generally need 2% of concrete volume, considering tension reinforcement and stirrups.
4. Steel in columns:
Columns need 2.5–3% of concrete volume due to higher axial + bending loads.
5. Steel in footings:
Footings require 0.8–1% of concrete volume.
Steel Weight & Formula
6. Standard formula for steel weight:
Weight (kg/m) = (D² ÷ 162), where D = bar diameter in mm.
Example: 12 mm bar = (12² ÷ 162) = 0.89 kg/m.
7. Steel in kg/m² of slab area:
Residential RCC slab ≈ 4–5 kg/m². Commercial ≈ 6–7 kg/m².
8. Steel in kg/m³ of RCC:
≈ 80–100 kg/m³ for residential.
≈ 110–130 kg/m³ for commercial.
9. 1 ton of steel provides:
≈ 135 running meters of 16 mm bar.
≈ 211 running meters of 12 mm bar.
≈ 530 running meters of 8 mm bar.
10. Thumb rule: Slab reinforcement spacing:
8 mm @ 150 mm c/c in distribution, 10–12 mm @ 150–200 mm c/c in main bars.
Overlaps & Development Length
11. Overlap in tension zone:
= 50 × bar diameter (50d).
Example: 16 mm bar → 16 × 50 = 800 mm lap length.
12. Overlap in compression zone:
= 40d.
Example: 20 mm bar → 20 × 40 = 800 mm lap length.
13. Maximum % of lap splices in one section:
Not more than 50% of bars should be spliced in the same section.
14. Development length (Ld):
Ld = (Φ × σs) ÷ (4 × τbd). For Fe415 in M20 concrete, approx. 47d.
Example: 16 mm bar → 47 × 16 = 752 mm.
15. Hooks in bars:
Standard hook = 9d extension at each end.
For stirrups, total hook length = 2 × 9d = 18d.
Bends, Cranks & Chairs
16. 45° bend length: = 1d.
17. 90° bend length: = 2d.
18. 135° bend length: = 3d.
These are added to cutting length in BBS.
19. Crank length in slab:
= (0.42 × Depth of slab) + extra 0.1 m.
20. Chair bar height:
= Slab thickness – Cover top – Cover bottom – Dia of top & bottom bars.
Rule: Provide chairs @ 1.0–1.5 m spacing.
Practical Consumption
21. Steel in one-storey residential building:
≈ 3–3.5 kg/sq.ft of built-up area.
22. Steel in commercial building:
≈ 5–6 kg/sq.ft due to higher live loads & spans.
23. Steel in water tanks:
≈ 130–150 kg/m³.
24. Steel in bridges/heavy structures:
≈ 200–250 kg/m³ depending on loading.
25. Weight of binding wire:
≈ 1–1.5% of steel weight.
Example: 1000 kg steel requires ~10–15 kg binding wire.
Wastage & Losses
26. Steel wastage at site:
≈ 2–3% cutting wastage + 1–2% due to bending, theft, rusting → total 5% allowance.
27. Overweight & underweight steel:
TMT bars may vary ±2% from theoretical weight. Always cross-check with IS 1786 charts.
28. Corrosion wastage allowance:
For coastal projects, add 2% extra steel to account for rusting loss over time.
29. Steel in couplers (lap replacement):
Couplers save 8–10% steel wastage in high-rise construction.
30. Scrap recovery:
≈ 2% of steel weight can be recovered as scrap (credits in BOQ).
Site Handling & Storage
31. Stack bars on wooden sleepers: minimum 150 mm above ground to prevent rusting.
32. Cover bars with tarpaulin/plastic sheet.
33. Store by diameter and length for easy cutting.
34. Straightening coil bars causes 1–2% elongation loss.
35. Never bend/re-bend bars more than once — reduces strength.
Design-Oriented Thumb Rules
36. Minimum steel in slab: = 0.12% (HYSD bars), 0.15% (mild steel).
37. Minimum steel in column: = 0.8% (min), 6% (max) of gross area.
38. Minimum bars in column: = 4 (rectangular), 6 (circular).
39. Pitch of stirrups in column: ≤ D/2 or 300 mm, whichever is less.
40. Lap splicing not allowed in bars >36 mm dia.
Weight Quick Reference
41. 8 mm bar: 0.395 kg/m.
42. 10 mm bar: 0.617 kg/m.
43. 12 mm bar: 0.888 kg/m.
44. 16 mm bar: 1.58 kg/m.
45. 20 mm bar: 2.47 kg/m.
46. 25 mm bar: 3.85 kg/m.
47. 32 mm bar: 6.31 kg/m.
48. 40 mm bar: 9.86 kg/m.
49. Formula check: Weight/m (kg) = D²/162.
50. Total steel weight: = Σ (Length × Weight/m) for all bar diameters.
