IS 808:1989 is the Indian Standard (BIS) for dimensions for hot rolled steel beam, column, channel and angle sections. IS 808 provides standard dimensions, cross-sectional areas, mass, and section properties (such as moment of inertia, radius of gyration, and section modulus) for hot-rolled steel beams, columns, channels, and angle sections. Structural engineers and steel detailers rely on this code to select standardized Indian steel profiles (like ISMB, ISMC, ISA) and use their geometric properties for safe structural design and BIM modeling.
Specifies the dimensions, weights, and section properties of hot rolled steel structural sections.
Depth range, masses and key dimensions for ISMB / ISLB / ISWB / ISMC / ISA structural sections used in IS 800 steel design.
| Reference | Value | Clause |
|---|---|---|
| ISMB — depth range | 100 – 600 mm (ISMB 100 to ISMB 600) | Cl. 5 (Table) |
| ISMB 200 — mass per metre | 25.4 kg/m | Table |
| ISMB 300 — mass per metre | 44.2 kg/m | Table |
| ISMB 450 — mass per metre | 72.4 kg/m | Table |
| ISMB 600 — mass per metre | 122.6 kg/m | Table |
| ISLB — depth range | 100 – 600 mm | Table |
| ISWB — depth range | 150 – 600 mm (wide flange) | Table |
| ISHB — section type | Heavy weight, columns 150 – 450 mm | Table |
| ISMC — channel range | 75 – 400 mm | Table |
| ISMC 200 — mass per metre | 22.1 kg/m | Table |
| ISMC 300 — mass per metre | 35.8 kg/m | Table |
| ISA (equal angle) — sizes | 20×20 to 200×200 mm (varied thicknesses) | Table |
| ISA 75×75×6 — mass per metre | 6.8 kg/m | Table |
| ISA 100×100×10 — mass per metre | 14.9 kg/m | Table |
| Unequal angle — typical | ISA 100×75×8, 150×115×10 etc. | Table |
| I-section flange taper (ISMB) | 8 % (98° flange-web angle) | Cl. 5 |
| Tolerance — depth (rolled section) | ± 2.0 mm (typical for ≤ 200 mm) | Cl. 7 (Table) |
| Tolerance — flange width | ± 2.0 to ± 4.0 mm by section | Cl. 7 (Table) |
| Mass tolerance per length | ± 2.5 % of theoretical | Cl. 7 |
| Standard length supplied | 10 – 13 m (typical mill lengths) | Cl. 8 |
| Density used for mass calc | 7850 kg/m³ | Cl. 5 |
| Steel grade reference | Per IS 2062 (Fe410 / E250 default) | Cl. 4 |
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
IS 808 specifies dimensions, weight, and section properties for hot-rolled structural steel sections commonly used in Indian construction. The 2021 revision replaced the 1989 edition; both are referenced in older designs.
You reference IS 808 whenever: - Selecting a steel section for a beam, column, or truss member - Computing section properties (I_xx, I_yy, Z_x, Z_y, radius of gyration) for IS 800:2007 design - Preparing steel take-offs (weight per metre for each section) - Specifying sections in drawings (designation like 'ISMB 300') - Comparing Indian rolled sections to international equivalents (UB, UC per EN 10365; W, S shapes per ASTM A6)
IS 808 covers ~120 standard sections across 8 families: - ISMB — Indian Standard Medium Beam (most common for beams) - ISLB — Indian Standard Light Beam (lighter alternative to ISMB) - ISWB — Indian Standard Wide Flange Beam (wider flanges than ISMB for lateral stiffness) - ISHB — Indian Standard Heavy Beam (heaviest I-section, for columns and heavy beams) - ISJB — Indian Standard Junior Beam (very light, for secondary members) - ISMC — Indian Standard Medium Channel (C-section, for purlins, bracings, staircase stringers) - ISA — Indian Standard Angle, both Equal (ISA ___ × ___ × t) and Unequal (ISA ___ × ___ × t)
Beams (flexural members): - ISMB is the default. Good balance of strength, stiffness, availability, and price. - ISLB is 15-25% lighter than ISMB for the same depth. Use when self-weight matters (long spans, lightweight roof, tall columns where cumulative weight affects foundations). - ISWB has wider flanges — use when lateral-torsional buckling governs (unbraced beam lengths > 6 m, crane girders, beams with limited lateral restraint).
Columns (axial + bending): - ISHB is preferred. The heavy flanges and web give radii of gyration near-equal about both axes, reducing susceptibility to buckling about the weaker axis. - ISMB can be used for lightly loaded columns up to 3-4 storeys in small buildings. - Built-up box sections or channels back-to-back are common for heavier columns where a single ISHB is inadequate.
Purlins and secondary members: - ISMC (channels) are the standard purlin section. ISMC 100-200 cover most industrial shed roof purlins. - ISA equal angles for bracings, struts, and tension members. - ISA unequal angles for eaves members and connections where asymmetry helps.
Trusses: - Top chord (compression): ISHB or double-angle back-to-back for compact trusses; built-up sections for large spans. - Bottom chord (tension): ISMB, ISA angles, or double channels. - Diagonals and verticals: ISA angles (single or double) are standard.
For a 7 m simply-supported beam in a small industrial building, factored UDL 25 kN/m. Fe 250 steel. Compare three options from IS 808.
Option A — ISMB 400 (55 kg/m): I_xx = 20,458 cm⁴ Z_p = 1,176 cm³ r_y = 2.84 cm Weight for 7 m: 55 × 7 = 385 kg
Option B — ISLB 400 (40 kg/m): I_xx = 15,549 cm⁴ (-24%) Z_p = 869 cm³ (-26%) r_y = 2.98 cm Weight for 7 m: 40 × 7 = 280 kg (-27%)
Option C — ISWB 400 (67 kg/m): I_xx = 23,707 cm⁴ (+16% vs ISMB) Z_p = 1,290 cm³ (+10% vs ISMB) r_y = 4.50 cm (+58% vs ISMB) — huge LTB benefit Weight for 7 m: 67 × 7 = 469 kg (+22%)
Flexural check (unfactored moment for comparison): M_u = wL²/8 = 25 × 7²/8 = 153 kNm Required Z_p per IS 800: Z_p,req = M_u × γ_m0 / f_y = 153 × 10⁶ × 1.10 / 250 = 673 cm³
Lateral-torsional buckling check (unbraced top flange): For 7 m unbraced, Clause 8.2.2 of IS 800 penalizes weak-axis slenderness. - ISMB 400: slenderness L/r_y = 7000/28.4 = 246 → significant LTB reduction, likely reduces capacity 30-40% - ISLB 400: L/r_y = 7000/29.8 = 235 → similar LTB issue - ISWB 400: L/r_y = 7000/45.0 = 156 → much less LTB reduction, probably 15-20%
Decision: - If top flange is continuously restrained (slab, sheeting): ISLB 400 — lightest and cheapest. Saves 105 kg (27%) vs ISMB. - If top flange is unbraced over 7 m: ISWB 400 — LTB benefit outweighs extra weight. Alternative: use ISMB 400 with mid-span lateral bracing.
This example shows why section-family selection matters as much as size. IS 808 gives you ~30% weight range across families at the same nominal depth.
1. Defaulting to ISMB for every section. ISMB is popular but often not optimal. ISLB saves 20-30% weight for beams with continuous lateral restraint. ISHB is better for columns (near-equal r_x and r_y). Check if other families give better utilization before specifying ISMB.
2. Confusing Ze and Zp. IS 808 tables provide both elastic section modulus (Z_e) and plastic section modulus (Z_p). IS 800:2007 Limit State Method uses Z_p for plastic sections and Z_e for semi-compact. Using Z_e in LSM calculations is conservative by ~12-15%.
3. Ignoring weak-axis properties for columns. For axially loaded columns, both r_x and r_y matter because buckling can occur about either axis. ISMB columns have r_y ≈ 0.25 × r_x — susceptible to weak-axis buckling. ISHB has r_y ≈ 0.45 × r_x — much better for columns.
4. Using 1989 section properties for 2021-specified sections. The 2021 revision made minor adjustments to flange thicknesses and section properties for a few sections. If your design references IS 808:1989 but the supplier delivers per IS 808:2021, properties differ by < 2% but the nominal designation may be the same. Check mill certificate against IS 808:2021 tables.
5. Specifying non-standard sizes. IS 808 covers standard rolled sections. Specifying ISMB 275 (a size that doesn't exist) forces the contractor to either substitute with ISMB 250 (under-design) or custom-roll (60% price premium and 8-12 week delivery). Always verify that the designation exists in IS 808 tables before specifying. Use the next-larger IS 808 size or a built-up section instead.
IS 808:1989 was the de facto standard for 32 years. The 2021 revision modernized the publication: added parallel-flange sections (IPE, HE equivalents), expanded property tables, and clarified tolerances.
Field reality: most Indian mills continue to roll the traditional tapered-flange ISMB, ISLB, ISWB profiles (per 1989 dimensions). Parallel-flange sections (IPE, HE) introduced in IS 808:2021 are still imported — not yet in domestic production at scale. For cost-sensitive projects, stick with traditional sections; for tall buildings and specialized projects, IPE/HE can be sourced from Germany/Korea at 10-15% premium.
Handbook tip: The ratio r_y / r_x for a section is the best single indicator of its suitability as a column. Target r_y / r_x > 0.4 for columns; IS 808 sections that meet this: ISHB (all sizes), IPE/HE (parallel flange), and double-angle combinations. Avoid single ISMB and ISLB as columns without bracing.
Procurement tip: Indian mills roll ISMB, ISLB, ISMC, ISA daily. ISWB, ISHB are rolled in batches (monthly). ISJB and some larger ISHB sizes are rolled only against order, with 8-12 week lead time. Plan procurement accordingly — major project shutdowns have occurred from designers specifying sections that had 3-month lead time without accounting for it.
Cross-check specification with supplier availability at DD stage; don't wait until CD.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Section Compared | ISMB 300 | IPE 300 | EN 10365:2017 |
| Depth (h) | 300 mm | 300 mm | EN 10365:2017 |
| Flange Width (b) | 140 mm | 150 mm | EN 10365:2017 |
| Web Thickness (t_w) | 7.5 mm | 7.1 mm | EN 10365:2017 |
| Flange Thickness (t_f) | 12.4 mm | 10.7 mm | EN 10365:2017 |
| Flange Geometry | Tapered Flange | Parallel Flange | EN 10365:2017 |
| Mass per Meter | 44.2 kg/m | 42.2 kg/m | EN 10365:2017 |
| Moment of Inertia (Ixx) | 8603.6 cm^4 | 8356 cm^4 | EN 10365:2017 |