THE BASICS · DAY 006 / LESSON 1
Purlins: the plain-English version
Purlins are secondary roof members, commonly formed as C or Z sections. [1]
MBMA QuickStart Guide, printed page 25, describes roof loads passing from panel to purlin to rafter.
Illustrative geometry
If primary frame lines are 20 ft apart, a purlin spanning that bay has a 20 ft support-to-support layout span. Laps and end conditions determine its actual manufactured length.
Start by separating the definition from the dimensions or requirements on a specific project. The reference below provides a concrete fact, its limits, and a practical example.
Sources & scope
- MBMA — Metal Building Student Competition QuickStart Guide ↗
Definitions and framing concepts; page references are included with each fact.
Source content checked October 14, 2026. Worked examples use stated assumptions; they are not project designs, prices, or site-specific requirements. Code editions and manufacturer specifications are identified so their limits are clear.
View the complete source library →The day is part of the BeamWerx learning curriculum; it is not a publication date.