Rafter Purlins
The Structural Backbone of
Every Industrial Roof.
High-performance insulated sandwich roof panels with PIR/PU/mineral wool core.
Superior thermal efficiency, fire-rated options. Factory-direct supply.
Rafter purlins span between the primary portal or truss frames of industrial buildings, directly supporting the roofing sheets
and transferring all roof loads back to the main frame.
As a specific application of Z, C and Sigma purlin sections, rafter purlins are dimensioned and placed according to the span,
loading and sheeting weight of each unique building design
No Site Drilling Required
Stock 7.5m & 12.0m
Factory-Cut to Length
Full Project Engineering
Service
G550 High-Tensile Steel
Rafter Purlin Specifications
All rafter purlins are cold roll-formed from G550 pre-galvanised Z275 steel — offering up to 50% weight savings over traditional hot-rolled angles, channels or hollow sections. Pre-punched holes at factory tolerances eliminate site drilling; custom lengths are cut and dispatched to your schedule.
| Specification | Detail |
|---|---|
| Available Sections | Z Purlin · C Purlin |
| Span Range | 3.0m – 8.0m between primary rafters / portal frames |
| Purlin Spacing | 1.0m – 2.5m centres (load and sheet span dependent)) |
| Thickness Options | 1.2mm · 1.5mm · 1.8mm · 2.0mm · 2.4mm · 3.0mme |
| Depth Range | 7.5m and 12.0m standard; custom cut available |
| Engineering Support | Full project engineering service available on request |
| Hole Punching | Factory pre-punched to specification — no site drilling |
| Material Savings | Up to 50% structural steel cost reduction vs. traditional sections) |
Rafter Purlin Section Types
Three cold-formed section profiles are used as rafter secondary roof members — Z, C and Sigma. Each profile has specific structural advantages suited to different span configurations, loading conditions and installation methods. Choose the correct profile using the free design software provided.
Long Span Preferred
Z Purlin
Z purlins can replace traditional angles, channels or hollow sections with up to 50% structural steel cost savings.
Versatile & Economical
C Purlin
C purlins are the standard workhorse rafter purlin for shorter single-span bays and wall girt applications. Their open channel section is easy to fix and align on site.
Full Structural Purlin Section Range
Polyhouse & Special Use
U Purlin Section
U sections are widely specified for polyhouse construction and other specialist applications.
Gable End Specialist
L Purlin (Angle Section)
L angle purlins are specifically designed for gable end framing in pre-engineered buildings.
Residential & Commercia
Hat Section Purlin
Hat sections feature two outward flanges with two vertical sides forming a distinctive hat profile.
Custom Engineering
Special Section Purlins
For non-standard structural requirements, special section purlins are custom roll-formed to project specifications.
Structural Accessories
& Drainage Systems
A complete secondary steel system extends beyond purlins. Gutter sections manage rainwater drainage, sag rods provide lateral alignment for purlins and girts, and foundation bolts anchor the entire structure securely to its concrete base.
Gutter Section — Factory
Roof Drainage
The gutter system is one of the most critical elements of any industrial roof. Poor installation leads to permanent maintenance problems.
Sag Rods — Lateral Support
for Purlins & Girts
Sag rods pass through C or Z purlin webs to provide lateral alignment and restrain the tendency to bend laterally and twist under load.
Foundation Bolts — Structural Anchoring
Foundation bolts anchor the primary steel frame to its concrete foundation, ensuring the structural integrity of the entire building system.
Structural Performance with Lower Cost
1.Up to 50% Structural Steel Savings
Cold-formed Z and C purlins replace angles, channels and hollow sections at a fraction of the weight and cost — validated by project after project in industrial construction.
2. Assured Dimensional Accuracy
Roll-forming to tight factory tolerances ensures consistent depth, flange width and hole positioning — critical for rapid, accurate erection on site.
3. High-Tensile G550 Steel
A minimum yield strength of 550 MPa and Z275 galvanised coating ensures every purlin delivers the structural performance and corrosion resistance specified.
4. No Site Drilling or Cutting
All holes pre-punched to specification at the factory. Custom cut lengths dispatched ready to erect — reducing site labour, waste and programme risk.
5. Low Transport Cost
Lightweight cold-formed sections nest and stack efficiently, reducing transport volume and cost compared to equivalent hot-rolled sections.
6. Long Service Life
Galvalume AZ150 steel facings with polyester or PVDF coatings provide corrosion resistance exceeding 25 years in most environments.
7. Lapped Z Systems for Long Spans
Z purlin nesting at internal rafter supports creates a continuous-beam effect — extending effective spans up to 8.0m between frames without increasing steel weight.
8. Full Project Engineering Service
For complex or non-standard configurations, a complete engineering service covers section selection, load analysis, span tables and design documentation.
6. Long Service Life
Galvalume AZ150 steel facings with polyester or PVDF coatings provide corrosion resistance exceeding 25 years in most environments.
Cold-formed rafter purlins consistently outperform traditional hot-rolled sections on cost, weight and installation speed — without compromising on structural performance. The secondary roof structure accounts for a significant portion of total steel tonnage in any industrial building; optimising it with the correct purlin section delivers measurable project savings.
Where Rafter Purlins Are Specified
Industrial Warehouses
Large-span logistics and distribution facilities requiring fast envelope installation.
Agricultural Buildings
C and Z rafter purlins for farm stores, grain stores and livestock housing.
Pre-Engineered Buildings (PEB)
Rafter and gable end purlins are core components of every PEB secondary structure.
Commercial & Retail
Sigma and Z purlins for wider bay centres on showrooms, distribution centres and retail sheds.
Polyhouses & Horticulture
U section purlins for controlled-environment agriculture and polyhouse roof structures.
Process & Manufacturing Plants
Sugar factories, FMCG, petrochemical and food processing facilities — long-span rafter purlins with corrosion-resistant coatings.
Why Leading Industries Trust Geometric Steels
18 Years of Innovation & Excellence
Feature
Product Range
Flashing Length
Manufacturing
Technical Support
Customization
Quality Certifications
Experience
Geographic Reach
Thermal Innovation
Sustainability
Geometric Steels
64 products – Complete solution
5 meters (industry-first)
In-house, ISO certified
Complete BOQ & site supervision
Made-to-order, 1–12m lengths
ISO, CE, IAF certified
17+ years, 52 sugar factories
India + exports to 7 countries
METAhybrid® R-4.2
100% recyclable materials
Industry Standard
Limited range
2.5 meters
Often outsourced
Limited support
Standard sizes only
Variable
Varies
Limited
Standard options
Variable
Frequently Asked Questions
Z, C and Sigma (Zed, Cee and Sigma) cold-formed sections are the most commonly specified rafter purlins. Z purlins are preferred for longer spans and lapped systems because their asymmetric shape allows nested overlapping at supports. C purlins suit shorter single-span bays. Sigma sections deliver enhanced stiffness for demanding load combinations where standard Z or C sections would require excessive thickness.
Standard rafter purlin designs cover spans from 3.0m to 8.0m between primary frame rafters. For lapped Z purlin systems, the effective span can be extended further by overlapping adjacent lengths at internal rafter supports — creating a continuous beam with improved load distribution. Span suitability for your specific loading and sheeting combination is confirmed using free engineering design software and load tables provided with every project enquiry.
Standard rafter purlin designs cover spans from 3.0m to 8.0m between primary frame rafters. For lapped Z purlin systems, the effective span can be extended further by overlapping adjacent lengths at internal rafter supports — creating a continuous beam with improved load distribution. Span suitability for your specific loading and sheeting combination is confirmed using free engineering design software and load tables provided with every project enquiry.
Rafter purlins are manufactured from G550 pre-galvanised Z275 steel — a high-tensile cold-rolled steel with a minimum yield strength of 550 MPa. The Z275 zinc coating (275 g/m² total both sides) provides long-term corrosion protection without the need for additional site painting in most industrial environments. C purlins are also available in 240 MPa and 350 MPa grades for applications where lower strength is sufficient.
Yes. Free engineering design software and comprehensive span and load tables are provided for all standard rafter purlin applications, allowing engineers to select and verify the correct section, thickness and spacing for their project. A full project engineering service is also available for complex or non-standard configurations — covering section selection, load analysis and design documentation. Contact us with your frame centres, bay spacings and roof loads to get started.m suitable for use in high-risk occupancies, buildings over 18m, public assembly buildings, healthcare facilities and any project where the building regulations or insurer stipulate non-combustible roof construction.