Steel Section Guide — Find and Compare IS 808 Sections
Not sure what ISMB, ISMC or ISA means? Answer four quick questions — we'll identify the right section family for your application.
IS 808:1989 defines 7 structural steel section families used in Indian fabrication — ISMB, ISMC, ISHB, ISA Equal, ISA Unequal, SHS, and RHS.
- Use the finder below to identify which family suits your application, then compare two sizes side by side.
- All property data is sourced from IS 808:1989 and IS 4923:1997.
- This tool does not perform structural calculations. Always verify with a qualified engineer per IS 800:2007.
Find the Right Section Family
Step 1 — What is your application?
Step 2 — What does the member carry?
Step 3 — What is your design priority?
Step 4 — What availability do you need?
⚠ This guide identifies section families based on common applications. It does not perform structural calculations and does not recommend specific sizes or load capacities. Final section selection must be verified by a qualified structural engineer using IS 800:2007, applicable loading standards (IS 875), and project-specific design calculations.
Understanding IS 808 Section Families
IS 808:1989 governs structural steel section dimensions in India. IS 800:2007 governs structural design. IS 2062 governs steel grades. IS 875 governs loading. These four standards work together — a fabricator selects a section shape from IS 808, verifies grades against IS 2062, and relies on a structural engineer to confirm adequacy under IS 800 and IS 875.
ISMB — Indian Standard Medium-weight Beam
The standard I-section beam in Indian structural fabrication. Optimised for bending loads in the strong axis (Ixx), making it the most common choice for primary load-carrying beams. 14 standard sizes from 100 mm to 600 mm depth per IS 808:1989.
- Building floor beams
- Industrial shed primary beams
- Mezzanine framing
ISMB 100–300 at most yards; 350–600 may require ordering.
See all ISMB sizes →ISMC — Indian Standard Medium-weight Channel
The standard channel section. One web, two flanges on one side — the open face makes it ideal where only one connection surface is needed, or where flange geometry suits purlin bolting. 11 standard sizes from 75 mm to 400 mm depth per IS 808:1989.
- Roof purlins
- Secondary framing and lintel beams
- Cold-formed connections
ISMC 75–200 at most yards; 250–400 may require ordering.
See all ISMC sizes →ISHB — Indian Standard Heavy-weight Beam
Wide-flange beam section with equal flanges. Larger flange width provides higher radius of gyration in the minor axis (ryy), making it more resistant to lateral buckling in columns and heavily loaded beams. 8 standard sizes per IS 808:1989.
- Heavy industrial columns
- Transfer beams
- High-load fabrications
Less commonly stocked — order from mill distributor.
See ISHB section properties →ISA Equal Angle
Two equal legs at 90°. The most widely used bracing section in Indian light-to-medium steel fabrication. Efficient in tension and as part of triangulated frames. 38 standard sizes per IS 808:1989.
- Roof truss members and bracing
- Purlins (small spans)
- Frame stiffeners
ISA 50×50 to 100×100 at most yards.
See all ISA Equal Angle sizes →ISA Unequal Angle
Two legs of different lengths at 90°. Used when the connection or loading condition requires a longer leg for bolt rows or when the two legs perform structurally different roles. Defined in IS 808:1989.
- Gusset plate connections
- Staircase stringers
- Rack framing
Less common — check yard stock before specifying.
See ISA Unequal Angle weight chart →SHS — Square Hollow Section
Equal square cross-section with hollow core. Good torsional stiffness and clean architectural appearance. Covered under IS 4923:1997.
- Columns in light framing
- Gate frames
- Architectural structures
SHS 40×40 to 100×100 at most yards.
See all SHS sizes →RHS — Rectangular Hollow Section
Rectangular hollow section. High bending strength in one axis with structural efficiency. Covered under IS 4923:1997.
- Beams in light framing
- Fascia members and railing posts
- Architectural applications
Standard sizes at most yards.
See all RHS sizes →Compare Two Sections Side by Side
⚠ This guide identifies section families based on common applications. It does not perform structural calculations and does not recommend specific sizes or load capacities. Final section selection must be verified by a qualified structural engineer using IS 800:2007, applicable loading standards (IS 875), and project-specific design calculations.
Frequently Asked Questions
What is the difference between ISMB and ISMC?
ISMB (Indian Standard Medium-weight Beam) is a symmetrical I-section with flanges on both sides of the web, used as a primary beam for bending in the strong axis per IS 808:1989. ISMC (Indian Standard Medium-weight Channel) has flanges on one side only, making it the standard choice for roof purlins and secondary framing where a single connection face is needed. Both are hot-rolled sections defined in IS 808:1989.
Which steel section is used for roof purlins in India?
ISMC (Indian Standard Medium-weight Channel) is the most commonly used section for roof purlins in Indian structural fabrication. The channel profile bolts directly to rafter flanges without additional cleats. ISMC 75 to ISMC 200 are the standard purlin sizes for industrial shed roofs. Hot-rolled ISMC sections per IS 808:1989 remain the standard for medium and heavy industrial applications.
What does ISMB 250 mean in IS 808?
ISMB 250 is an Indian Standard Medium-weight Beam with a nominal depth of 250 mm, defined in IS 808:1989. The designation follows the format: IS section type followed by nominal depth in millimetres. ISMB 250 weighs 37.3 kg/m, has a cross-sectional area of 47.5 cm², moment of inertia Ixx of 5131 cm⁴, and section modulus Zxx of 410.5 cm³ per IS 808:1989.
When should I use ISHB instead of ISMB?
ISHB (Indian Standard Heavy-weight Beam) has wider flanges relative to its depth compared to ISMB, giving it a higher radius of gyration in the minor axis (ryy). This makes ISHB sections more resistant to lateral buckling in columns and heavily loaded compression members. ISHB is typically specified per IS 808:1989 when minor-axis slenderness is a governing consideration under IS 800:2007.
What is the difference between ISA equal angle and ISA unequal angle?
ISA Equal Angle has two legs of equal length (for example ISA 75×75×6), making it symmetric and interchangeable in orientation. ISA Unequal Angle has two legs of different lengths (for example ISA 100×75×8), used when the connection geometry or the structural role of each leg differs. Both are defined in IS 808:1989. ISA Equal Angle is significantly more common in Indian fabrication and available at most steel yards.
Calculate the total weight of your selected section for any length using the free Metal Weight Calculator.
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