Kumar IronThe sections you will hear about
- Square hollow section (SHS), for example 25 x 25 mm or 40 x 40 mm: gate frames, grills, railings, columns.
- Rectangular hollow section (RHS), for example 50 x 25 mm or 60 x 40 mm: gate rails, purlins and shed frames.
- Round pipe (CHS), by outside diameter or nominal bore: gate posts, handrails, pergolas, light structures.
- Hollow sections for structural use follow IS 4923. Tubes for structural work follow IS 1161. Water or general purpose pipes follow IS 1239, which have different wall thickness classes (light, medium, heavy).
Thickness decides strength
Two tubes of the same outer size can differ a lot. A 40 x 40 mm tube at 1.6 mm is far weaker and lighter than 40 x 40 mm at 3.0 mm. For gates and sheds, size and thickness together decide stiffness. Always state both when asking for a rate, for example 40 x 40 x 2.5 mm.
Typical sizes by use
These are common practical choices for small jobs, not structural design. For long spans, heavy loads or wind exposure, ask your engineer or fabricator to size the members.
| Use | Typical section | Typical thickness |
|---|---|---|
| Grill and railing frame | 25 x 25 mm SHS | 1.5 to 2.0 mm |
| Domestic swing gate (up to about 3 m) | 40 x 40 mm or 50 x 25 mm frame | 2.0 to 2.5 mm |
| Heavy or sliding gate | 50 x 50 mm or 60 x 40 mm | 2.5 to 3.2 mm |
| Gate post | 75 x 75 mm SHS or 3 inch round | 3.0 to 4.0 mm |
| Shed purlins (about 1.5 to 2 m spacing) | 50 x 25 mm to 75 x 40 mm RHS | 1.6 to 2.5 mm |
| Shed columns and truss members | 60 x 60 mm to 100 x 100 mm SHS | 2.5 to 4.0 mm |
Wide spans need heavier sections or a truss. A 6 m wide shed needs engineered members, not guesswork.
Work out the weight
Weight in kg per metre of a hollow section is the steel cross section area times density. Use: kg per metre = (cross section area in mm²) x 0.00785. For a square tube of side a and wall t (both in mm), area = t x (4a - 4t) = 4t(a - t).
| Section | Area (mm²) | kg per metre |
|---|---|---|
| 25 x 25 x 2.0 mm | 184 | About 1.44 |
| 40 x 40 x 2.0 mm | 304 | About 2.39 |
| 50 x 50 x 2.5 mm | 475 | About 3.73 |
| 75 x 75 x 3.0 mm | 864 | About 6.78 |
Actual weights vary slightly with corner radius and tolerance. Use the number to catch a tube that is clearly too thin, not to settle disputes to the last gram.
Buying and fabrication tips
- Ask for the thickness in mm, not just a gauge name, and check it with a vernier caliper at the tube wall.
- Prefer tube from a known maker with markings. Underweight tube is common in unbranded stock.
- Paint after fabrication: red oxide primer then enamel. Weld joints are rust starting points, so clean and prime them well.
- Use a hot dip galvanised or pre-galvanised tube for outdoor sheds near coast or heavy rain areas, if budget allows.
- Add angle or flat stiffeners at gate corners and use proper hinges and ball bearing wheels for sliding gates.
Frequently asked questions
- What size MS pipe is good for a house gate?
- For a normal swing gate up to about 3 m wide, a 40 x 40 mm or 50 x 25 mm frame at 2.0 to 2.5 mm thickness is common, with 75 x 75 mm posts.
- How do I find the weight of a square MS pipe?
- kg per metre = 4 x t x (a - t) x 0.00785, where a is the side and t the wall thickness in mm.
- What is the difference between IS 1239 and IS 4923 tubes?
- IS 1239 covers steel pipes for water, gas and general use in light, medium and heavy classes. IS 4923 covers hollow sections for structural use.
- Which MS section is best for a small shed?
- RHS purlins of 50 x 25 to 75 x 40 mm with SHS columns and truss members, sized for your span. Share your dimensions on WhatsApp and we will suggest sections and quote at the day's rate.