| Specification | SF-220 |
|---|---|
| Box section | 220 × 55 mm, wall 4 mm, 2 cells |
| Weight | 4.53 kg/m (about 27 kg per 6 m) |
| Max rafter spacing, W0 0.65 kPa (zone I) | 6.8 m |
| W0 0.95 kPa (zone II) | 6.1 m |
| W0 1.25 kPa (zone III) | 5.5 m |
| W0 1.55 kPa (zone IV) | 5.0 m |
| W0 1.85 kPa (zone V) | 4.7 m |
Spans are for plastic roof sheets or plastic roof tiles, purlins spaced at 660 mm, deflection limited to L/200. Spacings above 6.5 m need a separate calculation.
SF-220 or an intermediate rafter?
For frames 5 m or more apart, price both options. Example, 6 m frames at 0.95 kPa: without an intermediate rafter you need SF-220 at 4.53 kg/m; with one, the spacing drops to 3 m and SF-120 at 2.36 kg/m is enough. The purlins cost much less, but you pay for the extra rafter. Send your drawing and Santiago FRP will price both.
Why use rust-free purlins on large factory roofs?
Replacing rusted steel purlins on a large factory means scaffolding, stopping production and sometimes re-roofing. FRP does not rust in chemical fumes, salt air or ammonia, and never needs repainting. A 6 m SF-220 weighs about 27 kg; two people can carry it.
Frequently asked questions
What are the dimensions of SF-220?
SF-220 is a double-cell FRP box section 220 × 55 mm with a 4 mm wall, weighing 4.53 kg per metre.
What rafter spacing can SF-220 span?
With purlins at 660 mm under plastic roof sheets, SF-220 spans up to 6.8 m at 0.65 kPa, 6.1 m at 0.95 kPa, 5.5 m at 1.25 kPa, 5.0 m at 1.55 kPa and 4.7 m at 1.85 kPa basic wind pressure.
Which FRP purlin suits 6 m frames?
SF-220 at basic wind pressures up to 0.95 kPa. Above that, or to reduce purlin cost, add an intermediate rafter so the spacing is 3 m and use SF-120 or SF-160.