PEB purlin choice is driven mainly by span continuity and cladding fixation. Solar MMS profile choice is driven by table geometry, clamp/bolt pattern, and the foundation interface — and that difference decides which profile does the work.
Industrial steel structures
- Z-purlins dominate multi-bay PEB roofs because they nest and overlap at supports (sleeved/bolted laps), letting continuous-beam design reduce mid-span moment — the default for spans over 6 m.
- C-purlins suit single-span or simply-supported conditions — wall girts, shorter bays, mezzanine framing — where lapping isn't needed and the symmetric section simplifies connections.
- Hat sections serve as secondary framing — sub-purlins, furring channels — where a low profile depth against the cladding matters more than spanning capacity.
Ground-mount solar MMS
- C-sections are the default for primary members within a table, since most MMS tables are simply-supported rather than continuous — the lapping advantage Z offers in PEB roofs doesn't apply the same way, and a symmetric section simplifies module-clamp and bolt-hole punching.
- U-channels handle foundation-to-structure connections (pile caps, ground screws) and bracing, where torsional stiffness against wind-induced racking matters more than bending capacity.
- Z-sections appear on larger single-axis tracker or fixed-tilt designs with longer table spans, where the same continuous-beam economics that favour Z in PEB roofing start to apply.
- Hat sections show up as module-mounting rails, where a shallow, ribbed profile helps with clamp positioning.
Quick reference
| Profile | Primary PEB use | Primary Solar MMS use |
|---|---|---|
| Z | Multi-bay continuous purlins | Long-span tables, trackers |
| C | Single-span purlins, girts | Standard table rafters/purlins |
| Hat | Sub-purlins, furring | Module mounting rails |
| U | Bracing, minor framing | Foundation connections, bracing |
The short version for a spec conversation: PEB profile choice is about span continuity and cladding fixation; MMS profile choice is about table geometry, clamp pattern, and the foundation interface.
Not sure which profile fits your member schedule?
Send us the drawing or the member list. We will suggest the section for each member and confirm the size, thickness and punching before we price it.
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