C-purlin size and spacing.
Two decisions set a purlin layout: the section (2×3, 2×4 or 2×6, by how far it spans between frames) and the spacing (0.6–1.0m, by the roofing sheet it carries). The tables below cover typical Philippine practice — wind load per NSCP governs, and it governs hard in the typhoon belt. Sections and weights are on the C-purlins page.
Size by span
Purlin span = frame-to-frame (truss-to-truss) distance · normal roof loads
| Purlin span | Section | Thickness |
|---|---|---|
| Up to 3.0 m | 2×3 (50×75mm) | 1.2mm |
| 3.0 – 4.5 m | 2×4 (50×100mm) | 1.5mm |
| 4.5 – 6.0 m | 2×6 (50×150mm) | 1.5 – 2.0mm |
Rule-of-thumb for normal roof loads. Coastal and wind-exposed sites in the typhoon belt need heavier gauge or tighter framing than this table — that call is the engineer's, per the NSCP wind maps.
Spacing by roofing sheet
| Roofing sheet | Typical purlin spacing |
|---|---|
| 0.4mm corrugated / rib-type | 0.6 – 0.7 m |
| 0.5mm rib-type / long-span | 0.7 – 1.0 m |
| Tile-span and heavier profiles | Per the sheet manufacturer's batten spec |
Thinner sheet needs closer support or it drums and dents underfoot. When the sheet brand publishes a span table, use it.
Installation notes
- Set purlins with the lips up-slope so the section sheds water and takes screws on the flat flange.
- Lap purlins over supports, or run back-to-back pairs on long spans and at ridges.
- Add sag rods at midspan on runs above roughly 4.5m to keep lines straight during sheeting.
- The same sections run vertically as wall girts on steel-frame buildings.
How it's sold
Galvanized C-purlins from 2×3 up to 2×8, thickness 1.0–2.0mm, 6.0m standard length with longer lengths by order, delivered nationwide. The table covers the common roof sizes; 2×8 carries longer spans and heavier sheets per the design. Send your framing plan or purlin schedule and we quote it back the same day.
Common questions
What spacing between C-purlins?
0.6–0.7m for standard 0.4mm corrugated or rib-type sheets, up to about 1.0m for 0.5mm and heavier long-span profiles. Follow the roofing sheet manufacturer's span table where one exists.
2×3 or 2×4 C-purlin — which one?
Go by the purlin span, frame to frame: 2×3 up to about 3.0m, 2×4 for 3.0–4.5m, 2×6 for 4.5–6.0m. Longer spans or heavy sheets push you up a size or into a designed section.
What thickness should the purlin be?
1.2mm for short spans, 1.5mm for mid spans, 2.0mm at the long end. Note that nominal gauge varies by brand — a "1.2mm" coil can run 1.0–1.1mm actual — so confirm actual thickness on the quote.
C-purlin or steel tubular for roof framing?
Purlins are the roof standard: the C-profile takes bending across the slope efficiently and screws take cleanly to the flange. Tubular suits gates, frames and trusses, not purlin runs.
How far can a C-purlin span?
About 6.0m with a 2×6 at 2.0mm under normal roof loads. Beyond that — or anywhere wind-exposed — it is a design item: lapped or back-to-back purlins, closer frames, or a hot-rolled section per the engineer.
Related
Reviewed July 2026 · Southend Construction & Industrial Supplies, Dasmariñas, Cavite