1. horizontal structural beams that support the rafters of a roof
Usage: construction; architecture

Examples

• The carpenter installed purlins between the rafters to strengthen the roof structure.
• Metal purlins are commonly used in commercial building construction.
• The roof collapsed because the purlins were improperly spaced.
• We need to replace the damaged purlins before installing the new roofing material.
• The building code requires purlins to be placed every four feet.
• Steel purlins provide better support than wooden ones in large structures.