Kumar IronUpdated
In this guide
Start with the design, not the shop
Frame sizes depend on the span, height, wind load, sheet type and purlin spacing. A 10 metre span with a light roof and a 15 metre span with a heavy roof need different members. Get the span, bay spacing, height and roof slope written down before you buy anything. The Indian design codes that govern steel structures are IS 800 and the wind load code IS 875 (Part 3). Ask your fabricator to confirm the design against them.
Once the design is fixed, the material list follows from it. The steps below are in the order the crew will need them.
Frame members: pipe, angle, channel or beam
The frame carries the roof and the wind. Members are usually MS pipe or hollow section for columns and rafters, angle for bracing and small trusses, channel for purlins or light beams, and I-section or beam for heavier spans. The choice depends on the design, not on what is cheapest that day.
- Columns: pipe, hollow section or I-section, one length per column, plus any base plates.
- Rafters or trusses: angle, pipe or hollow section, cut to the roof pitch.
- Tie beams and bracing: angle or flat bar, to stop the frame racking in wind.
- Gusset plates and cleats: for joints where members meet, usually flat plate.
- Check the weight of each member with our angle, channel and pipe weight charts so you can total the steel in kilograms.
Purlins
Purlins are the horizontal members that carry the sheets. Light channel purlins and rectangular hollow section purlins are both common. The spacing depends on the sheet thickness and profile, so take the figure from the sheet maker's span table and not from a rule of thumb. Our purlin spacing guide gives the typical ranges and what to check.
| Item | Buy with | Note |
|---|---|---|
| Purlin members | Length per roof row, total metres | Order extra for lap and cut waste |
| Purlin cleats or clips | One set per purlin per rafter | Match the cleat to the purlin size |
| Bolts for purlin to rafter | Per connection | Use the grade the engineer specifies |
Sheets, fasteners and washers
Sheets are the biggest line on the bill, so their count comes from the cover width and length you worked out earlier. Fasteners are small in cost but cause most of the roof problems later, so do not run short. For metal sheets on steel purlins, a self-drilling screw with an EPDM washer is standard. Our fixing guide explains the screw length and spacing.
- Sheets: count from the effective cover width, plus cutting spares.
- Self-drilling screws with EPDM washers: at least one per fixing point, plus spares.
- J hooks and nuts if you use them on angle purlins.
- Ridge fixings and sealant, as the maker recommends.
Foundation bolts and footings
Each column needs a base that the frame can be fixed to. Anchor bolts, set into the concrete footing, hold the base plate down against uplift and sliding. The size and embedment depth come from the design. Set the bolts at the right position before the concrete sets, because bolts that are off by a few millimetres cause trouble at erection.
- Anchor bolts: quantity per column, as the design says.
- Base plates: one per column.
- Cement and aggregate for the footings: confirm the grade with the engineer.
- Nuts and washers for the anchor bolts.
Gutters, downpipes and ridge
A tin shed sends a lot of water off a short roof. Gutters and downpipes take it away from the walls and the animal or machine area. The ridge cap covers the top joint of the roof, and it must overlap at least the distance the maker specifies. Everest's guide says ridge caps should overlap by at least 100 mm.
- Gutter length: eave length on each side, plus bends and outlets.
- Downpipes: one per outlet, with brackets.
- Ridge cap: ridge length plus overlap at each joint.
- Gable and eave flashings: edge length on each side.
What to buy together, and what to check
Order the frame, purlins, sheets and fixings in one go if the dealer can deliver together. Buying in parts often causes a longer delay and a mismatch in finish or coating. Check that the purlin spacing matches the sheet thickness and profile in the maker's span table before the frame is fixed.
- Frame members in one lot, with sizes and lengths written on the list.
- Sheets, fixings, ridge and flashings as a second lot, matched to the design.
- Primer for any cut or welded steel, and paint for the frame.
- Welding electrodes or wire, and cutting discs, for the fabrication.
Send us your shed size and we can help you total the steel weight and sheet count. For prices, call or WhatsApp the store, because rates change.
Frequently asked questions
- Which steel is best for a tin shed frame?
- There is no single answer. The size and grade come from the design, and the engineer picks the member type for the span and load. Ask the fabricator to show the design basis.
- Do I need an engineer for a small farm shed?
- For a simple shed, a good fabricator with a clear design can often manage. For larger spans, a factory, or a roof that has to take heavy wind, get the design checked against IS 800 and IS 875.
- How many anchor bolts go in each column?
- It depends on the design and the load. The engineer or fabricator should specify the number, size and depth for each base.
- What should I buy first?
- Get the design and the member list first, then order the frame and purlins, then the sheets and fixings once the purlin spacing is fixed.