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Secondary Framing
Secondary framing for steel portal frame buildings: Z and C purlins, rectangular and channel purlins and high-frequency welded H-purlins that carry the roof and wall cladding to the primary frame. Cold-formed from galvanised coil to the spacing set by the cladding profile and the wind loads of the site.
What we fabricate in this sub-system
- Z-Section Purlins (EN 1993-1-3 / ASTM A653)
- C-Section Purlins (EN 1993-1-3 / ASTM A653)
- Rectangular Purlins (EN 1993-1-3 / ASTM A653)
- High-Frequency Welded H-Purlins (EN 1993-1-3 / ASTM A653)
- Channel Purlins (EN 1993-1-3 / ASTM A653)
Technical Specifications
| Item | Specification |
|---|---|
| Design basis | AISC 360 / EN 1993 |
| Execution class | EN 1090-2 EXC2 (certificate 2787-CPR-01627) |
| Welding | AWS D1.1 / EN ISO 9606 qualified procedures and welders |
| NDT | ISO 11666 / AWS D1.1, technicians to ISO 9712 or ASNT Level II |
| Corrosion protection | ISO 12944, system selected per site environment (C3–CX) |
| Documentation | MTRs, WPS/PQR, welder certificates, NDT and DFT reports with every shipment |
Section sizes, grades and tolerances for these components are issued with the quotation once your design basis and loads are received.
Advantages vs Engineering Considerations
| Advantages | Engineering Considerations |
|---|---|
| Galvanised to the specified coating massCold-formed purlins are rolled from galvanised coil to the zinc mass your specification names, up to Z275, with mill certificates attached. | Best suited to single-storey and low-rise buildings; multi-storey floors or heavy mezzanines call for a braced or moment frame instead. |
| Spacing set by the claddingPurlin and girt spacing follows the cladding profile, the wind uplift and any rooftop equipment, so panels are not fixed to an assumed grid. | Column-free spans increase rafter depth and foundation reactions; very long spans may be more economical as trusses or space frames. |
| Sag rods and bridging includedSag rods, bridging and cleats are quoted with the purlins so the secondary framing arrives as a complete set. | Frames are sized to the stated crane duty and loads; a later change of crane class or roof equipment needs a design check. |
| Nested for freightPurlins are bundled and nested in the web grooves of primary members during container loading, which keeps the secondary steel from adding containers. | Cold-formed purlins and girts reach their design capacity only with correct cladding fixing and bracing. |
Certifications & Compliance
Every shipment leaves with the documents an auditor asks for. Scroll the row and open any certificate at full size.
China Steel Structure Manufacturing Grade I
AISC Certification
CE Marking – EN 1090-2 (CPR 01627)
OTC Document of Validity
International Welder Certification
Enterprise Qualifications Portfolio
DG Packaging Certificate
Labor & Scaffolding Contracting
Explosion-Proof Certificate
Industrial Pipeline Installation GC1
Power Facility License
Have drawings or a BOQ ready? Send them through the form and our engineers reply with a preliminary assessment.
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Detailed Engineering & Shop Drawing Development
Utilizing advanced BIM platforms such as Tekla Structures, detailed 3D modeling and shop drawings are executed strictly in compliance with AISC 360 or Eurocode 3 (EN 1993). Connection designs are rigorously verified, with manufacturing drawings generated to ISO 2768-m tolerance standards. 100% clash detection with primary architectural and MEP systems is performed to ensure zero structural conflicts during field erection.
Nesting & Material Optimization
Intelligent nesting layouts are performed using advanced software like FastCAM/SigmaNEST in accordance with EN 10029 / ASTM A6 dimensional standards. Accounting for cutting kerf (2mm-5mm depending on plate thickness) and thermal contraction allowances, raw material utilization exceeds 92%. Offcuts are digitally barcode-tracked to ensure 100% mill test report (MTR) traceability.
Raw Material Incoming Inspection
All structural steel (Q355B/C/D, ASTM A572 Gr.50, S355JR/J2) must be accompanied by EN 10204 3.1 Mill Test Reports (MTR). Incoming quality control conducts 100% dimensional and visual inspections under ASTM A6 / EN 10029, verifying thickness tolerances (Class A/B) and internal lamination integrity via Ultrasonic Testing (UT) to ASTM A435. Chemical composition and mechanical properties are spot-verified by accredited 3rd-party labs.
CNC Cutting & Edge Preparation
Plate profiling and component cutting are executed via CNC oxy-fuel, high-definition plasma, and multi-kW fiber laser equipment. Cut surface quality strictly complies with EN ISO 9013 for perpendicularity and surface roughness (Range 3/4 tolerance). Multi-axis CNC beveling machines execute weld prep bevel angles within ±2.5° and root face dimensions within ±1.0 mm.
Primary Structural Welding
Welding is performed exclusively by AWS D1.1 or EN ISO 9606 certified welders using qualified Welding Procedure Specifications (WPS) supported by Procedure Qualification Records (PQR) per AWS D1.1 / ISO 15614. Submerged Arc Welding (SAW) and Flux-Cored Arc Welding (FCAW) dominate Complete Joint Penetration (CJP) and fillet welds. Heat input is strictly controlled, achieving weld quality levels conforming to ISO 5817 Quality Level B or AWS D1.1 standards.
Weld Distortion Straightening
Post-weld angular distortion, camber, and sweep are rectified using automated hydraulic flange straighteners and controlled thermal flame straightening. Heating temperatures for High-Strength Low-Alloy (HSLA) steels are strictly maintained between 600-650 Celsius (air-cooled, zero water quenching) to prevent microstructural degradation. Post-straightening straightness tolerances meet ±3 mm, conforming to EN 1090-2 Execution Class 2 (EXC2) and AISC COSP standards.
Non-Destructive Testing (NDT)
NDT protocols are operated by ISO 9712 / ASNT Level II certified NDT personnel. 100% of critical Complete Joint Penetration (CJP) welds undergo Ultrasonic Testing (UT per ISO 17640 / ASTM E164) or Magnetic Particle Testing (MT per ISO 17638 / ASTM E709). Radiographic Testing (RT) is applied as requested for heavy sections. Weld acceptance conforms strictly to ISO 11666 Acceptance Level 1 or AWS D1.1 criteria.
Trial Assembly & Shop Alignment
Complex geometries, long-span trusses, and heavy framing undergo 1:1 physical trial assembly or high-precision 3D laser scanning virtual assembly per EN 1090-2 / AISC requirements. Bolt hole alignment is verified (≥95% free-pass rate for high-strength bolts), and critical dimensions (span, camber, 3D spatial alignment) are verified within tight tolerance limits (±2.0 mm) to eliminate site fitting risks.
Surface Preparation & Protective Coating
Structural members undergo automated shot blasting to achieve SSPC-SP10 / NACE No. 2 / ISO 8501-1 Sa 2.5 cleanliness, with a surface profile (anchor depth) of 45-75 microns. High-performance protective coatings are applied using airless spray technology in compliance with ISO 12944 (C3 to CX corrosive environments), featuring Zinc-Rich Epoxy Primers, Epoxy Micaceous Iron Oxide Intermediate coats, and Polyurethane/Fluorocarbon Topcoats. Dry Film Thickness (DFT) is verified adhering strictly to the 90/10 rule.
Final Quality Inspection & Certification
Final Quality Control (FQC) performs a comprehensive audit, inspecting paint aesthetics (zero runs, pinholes, sagging), critical geometry, bolt hole pitches, and component mark traceability. A complete Manufacturing Data Report (MDR) comprising MTRs, NDT records, coating inspection logs, and Certificates of Conformance is compiled to support CE Marking (DoP under EN 1090) and AISC final acceptance.
Export Packaging & Logistics Protection
Protective packaging is engineered for containerized (40HQ/OT/FR) and breakbulk ocean freight under heavy maritime transit conditions. Structural members are bundled on heavy-duty steel skids with high-tensile steel strapping. Machined connections are wrapped with VCI anti-corrosion film, EPE foam padding, and heavy rubber cushions. All timber packing complies fully with ISPM 15 phytosanitary standards and IMO Cargo Stowage and Securing (CSS) rules.
Global Field Erection & Site Management
We deliver international site erection supervision and turnkey EPCM construction services adhering to OSHA 1926 safety protocols, AISC COSP, and EN 1090-2 erection standards. Field teams, led by multilingual HSE and QA/QC engineers, utilize high-precision total stations to maintain structural plumbness within H/1000 (25mm max). High-Strength Structural Bolting is executed via calibrated Wrench or Turn-of-Nut methods with 100% torque audit documentation.
Frequently Asked Questions
Can you supply purlins and girts for an existing portal frame from another fabricator?
Yes. Send the rafter and column spacing, cladding type and site wind loads; we size the purlins and supply cleats to suit the existing frame.
Which purlin is right for a roof carrying rooftop solar?
Usually a rectangular hollow section or a welded H-purlin at closer spacing; the panel weight, mounting rail layout and wind uplift decide it. Send the array layout and we check the purlins against it.
Z or C purlins — which should we specify?
Z sections lap at the supports and act continuous, which suits multi-span roofs and saves steel. C sections suit single spans, end bays and wall girts where lapping is not possible. Send the span, spacing and wind uplift and we propose the section rather than defaulting to one.
Do you supply the sag rods and bridging with the purlins?
Yes — sag rods, ties and bridging are quoted as part of this sub-system. Purlins delivered without their bridging is one of the most common causes of site delay in this category.
Can you supply this sub-system on its own, without the full frame?
Yes. We quote sub-systems separately where the scope makes sense — for example secondary framing or bracing against an existing structure. Send the BOQ and connection details of the receiving structure so the interfaces are engineered rather than assumed.
Which design code do you fabricate to?
Whichever your design specifies. Design intent to AISC 360 or Eurocode 3 (EN 1993), execution to EN 1090-2 EXC2 under certificate 2787-CPR-01627.
Do you substitute section sizes or grades?
Never without written approval. If a specified section has a long lead time we propose the alternative with the calculation showing equivalence, and you decide.
What documentation ships with these components?
Mill test certificates per heat, WPS/PQR, welder qualification certificates, NDT reports with technician level, and coating thickness records against the specified ISO 12944 system.
What is a realistic lead time?
The standard cycle for a single-building scope is 40 to 50 days: 1–2 weeks to shop drawings for your approval, then 4–5 weeks for procurement, fabrication, coating and loading.
Send Us Your Drawings or BOQ
Tell us the footprint, span, crane capacity and local loads — our engineering team reviews every request and replies with a preliminary assessment.
- Reviewed by our engineering team
- AISC certified · CE marked EN 1090-2 (EXC2)
- Mutual NDA available on request
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