Purlins and Girts: The Secondary Steel of a PEB
Purlins are the horizontal members spanning between roof frames that carry the roof sheeting; girts are their equivalent on the walls, carrying wall cladding. Together they are the secondary framing that transfers cladding loads into the main frames.
By Dhruv Agarwal · · 1 min read
Why it matters
Roof and wall cladding is only as secure as the steel it is fixed to. Purlins and girts carry wind suction, maintenance loads and the weight of the cladding into the frames, and in storms they are often where failures begin.
How it works in practice
| Member | Location | Typical section |
|---|---|---|
| Purlin | Roof, between frames | Cold-formed Z or C |
| Girt | Wall, between columns | Cold-formed Z or C |
| Eave strut | Roof-to-wall edge | Cold-formed C |
| Sag rod | Between purlins | Restrains them sideways |
Common mistakes
- Uniform spacing across the roof. Edge and corner zones see higher uplift.
- Omitting sag rods or bracing. Thin sections twist without restraint.
- Hanging loads without checking. Services, cable trays and solar panels add load purlins were not designed for.
Standards referenced
Cold-formed members under IS 801. Wind loads under IS 875 (Part 3).
Standards referenced
- IS 801 — Use of cold-formed light gauge steel structural members
- IS 875 (Part 3) — Wind loads on buildings