FRP Roof Purlin

An FRP roof purlin that does not need to be recoated in the chemical atmosphere your building sits in

Pultruded FRP C-section and Z-section purlin for industrial building roofs. Replaces galvanized steel purlin in chemical, coastal, and salt-spray environments where the conventional purlin fails within the asset life. Sized to the published section properties; structural PE stamp on request.

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SECTION PROPERTIES - START HERE

Section properties below are nominal for the published pultruded FRP profile. The structural PE uses these for span, deflection, and capacity checks against the project load case.

Profile	Section	Depth × Flange × Lip (mm)	Mass (kg/m)	Moment of inertia Ix (cm⁴)	Section modulus Sx (cm³)	Span at 1 kN/m (m)
C150	C-section	150 × 50 × 15	{{2.8}}	{{280}}	{{37}}	{{4.5}}
C200	C-section	200 × 60 × 20	{{3.6}}	{{580}}	{{58}}	{{5.5}}
C250	C-section	250 × 75 × 20	{{4.5}}	{{1,100}}	{{88}}	{{6.5}}
C300	C-section	300 × 80 × 25	{{5.4}}	{{1,900}}	{{127}}	{{7.5}}
Z200	Z-section	200 × 60 × 16	{{3.6}}	{{620}}	{{62}}	{{5.5}}
Z250	Z-section	250 × 75 × 18	{{4.5}}	{{1,180}}	{{94}}	{{6.5}}
Custom	per project	to 400 mm depth	per calc.	per calc.	per calc.	per calc.

Section properties are nominal. Project-specific properties are validated against the published datasheet on first article. Span estimate uses 1 kN/m uniform load and L/200 deflection limit; verify on project load case.

What the buyer is trying to solve

Structural engineers specifying the next industrial roof.

The buyers who arrive at this page are structural engineers and building contractors specifying the roof framing for an industrial building in a chemical, coastal, or salt-spray environment. The existing galvanized steel purlin has rusted; the existing painted steel purlin is on its third paint cycle; the project spec has specified a 25-year service life and the conventional purlin will not survive it. They want a purlin that meets the published section properties, accepts the same cladding fasteners as the conventional choice, and does not need to be recoated.

Lightweight

~ ¼ the weight of the equivalent galvanized steel purlin; reduces the structural demand on the building frame.

Corrosion proof

Vinyl-ester pultruded purlin rated for the same chemical atmosphere as the rest of the FRP roof and wall package.

Same fasteners

Compatible with self-drilling metal cladding screws; no special tools.

25-yr asset life

No recoat, no rust, no unplanned shutdown to replace corroded purlins.

Specifications

Profile family	C-section ({{150–300}} mm depth); Z-section ({{200–250}} mm depth); custom up to 400 mm
Mass	{{2.8–5.4}} kg/m for standard sections (verify on part drawing)
Resin system	Vinyl-ester (FR); isophthalic (economy); phenolic (HL3-rated) on request
Glass schedule	Continuous unidirectional roving + mat, balanced orthogonal
UV package	UV-9 inhibitor integral + UV-stable topcoat on visible surfaces
Fire performance	ASTM E84 Class A on request; ASTM D635 self-extinguishing
Volume resistivity	> 10⁸ Ω·cm (non-conductive)
Operating temperature	{{−50}} °C to {{+90}} °C continuous (resin dependent)
Cladding fastener compatibility	Self-drilling metal screws ({{#12, #14}}); pre-drilled on request
Anchor to rafter	Stainless A4 self-drilling bolts or through-bolts with isolating bushings
Color	Standard grey RAL {{7035}}; other RALs on request
Design life	{{25}} years in chemical atmosphere
Standard length	6 m and 12 m; custom up to {{18}} m

When not to specify FRP purlin

Cases where steel purlin remains correct.

Three cases where we redirect

Very heavy roof loads (snow zone above {{3 kN/m²}}). The FRP purlin has limited stiffness; in heavy-snow climates the project structural engineer will favor a steel section. Verify the span on first article.
Co-located with high-voltage equipment above the roof. FRP is non-conductive - that is the point - but lightning protection must be designed separately. If the project specifies a conductive purlin for lightning path, FRP is the wrong material.
Roof must support a heavy maintenance vehicle on the top surface. Walking the roof for maintenance is fine; rolling heavy equipment over the purlin span is a different load case and may exceed the section capacity.

Material comparison

Property	Galvanized steel C250	Aluminum C250	Enbuss FRP C250
Mass per metre	~ {{6.5}} kg/m	~ {{2.5}} kg/m	~ {{4.5}} kg/m
Moment of inertia Ix	~ {{600}} cm⁴	~ {{900}} cm⁴	~ {{1,100}} cm⁴
Coating cycle	{{24–36}} months	Anodize {{10–15}} yr	None
Salt-spray service life	{{5–10}} yr (red rust)	{{15–20}} yr (pitting)	{{25}}+ yr
Galvanic corrosion with aluminum cladding	Yes - needs isolation	No	No
Span at 1 kN/m load	~ {{6.5}} m	~ {{7.0}} m (deflection-limited)	~ {{6.5}} m
25-yr cost (chemical atmosphere)	2 recoat cycles + possible replacement	Some replacement	No recoat

Customization & OEM

Building contractors typically need a cut-to-length purlin with the project-specific hole pattern. We supply the purlin as cut lengths with pre-drilled holes where the cladding fastener pattern is known. Send the project drawing; first article {{6}} weeks; repeat {{3}} weeks.

Frequently asked questions

What is the typical lead time for a 4 km purlin order?

From PO to first delivery, typically {{8–10}} weeks for standard C200 / C250 sections in vinyl-ester grey. Custom section or color adds {{2}} weeks.

Does the purlin accept standard self-drilling cladding screws?

Yes. Self-drilling metal screws ({{#12, #14}}) drive directly into the FRP without pre-drilling on standard sections. For thicker sections, pre-drilling is recommended.

What is the design life?

{{25}} years in chemical atmosphere. Typical FRP pultrusion project life is set at {{25–30}} years for structural applications.

How is the purlin inspected in service?

Visual at annual walk-around; look for surface damage, UV chalking, or impact cracks. Any visible crack or fiber exposure is grounds for replacement. Inspection interval typically annual.

Does the purlin support a suspended ceiling?

Yes, on most sections. Suspend from the purlin flange with standard ceiling hangers; verify the local load on first article.

Can the purlin be supplied with a factory-applied fire-retardant topcoat?

Yes, ASTM E84 Class A topcoat is applied on request. Adds {{1}} week to lead time.

Is the purlin recyclable?

Vinyl-ester pultrusions can be shredded and used as filler in non-structural concrete. We offer a take-back program in pilot regions.

What documentation comes with each shipment?

Per shipment: dimensional inspection, resin lot certificate, ASTM E84 (if specified), structural PE stamp (on request), installation drawing.

Send a roof framing layout

Send the purlin spacing, the span, the roof cladding type, and the atmospheric class. We return a section sizing, a fixed quote, and the certification pack your structural PE needs.

Email a structural engineer