Roofing / Longitudinal roof member
Purlin
/ˈpɜːr.lɪn/noun
Middle English purlyn; origin uncertain.
Definition
A horizontal roof member running parallel to the ridge, spanning between trusses, rafters, or frames to support roof sheeting or common rafters.
Fig. 36 — Purlin: schematic studyNOT TO SCALE
Illustrative study — Purlin · AI-generatedSAMPLE IMAGE
Photo study — Purlin · AI-generated00:06
Structural & construction notes
Purlins carry roof loads in bending and often help brace the top chords of trusses. Spacing depends on the roof covering, snow and wind loads, and the purlin section.
An educational reference. Project-specific design requires professional guidance.