Purlin
A purlin is a horizontal roof framing member spanning between rafters or portal frames to carry roofing. Common in steel-framed sheds and metal roof systems.
Ask Chalkline about this →A purlin is a horizontal structural member running parallel to the eaves, spanning between rafters or portal frame columns, and carrying the roof cladding directly. In residential construction, purlins are common in steel-framed structures where the roofing sheet spans directly from purlin to purlin without an intermediate batten. In commercial and shed construction, C-section or Z-section steel purlins carry Colorbond or corrugated cladding over a portal frame.
The distinction from a batten is one of structural role: a purlin is the primary span member, carrying load back to the rafters or columns; a batten is a secondary, smaller member fixed to the top of rafters or purlins. Metal roofing span tables specify the maximum purlin spacing for the selected profile, steel grade, and wind classification. Exceeding the tabulated span without engineering advice is a compliance risk under AS 1562.1:2018.
Category: Roof structure / framing.
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Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency.