Purlin

Definition

A purlin is a timber supporting several rafters at one or more points, beams or struts that span across a roof to support the roof framing system.

Purpose

The purpose of purlins is to provide structural support to the roof, distributing loads from the roof covering to the primary structural framework, thereby enhancing stability and strength.

Examples of Use

• Purlins are used in residential roof construction to support roof decking and roofing materials.
• In agricultural buildings, purlins support large spans of roofing over barns and sheds.
• Commercial and industrial buildings often use metal purlins to support extensive roofing systems.

Related Terms

• Rafter: A structural member extending from the ridge or hip to the wall plate, supporting the roof deck and its loads.
• Truss: A framework of beams forming a rigid structure, often used in roofs.
• Beam: A structural element that primarily resists loads applied laterally to the beam's axis.

Notes

Purlins can be made from various materials, including wood, steel, or aluminum, depending on the requirements of the building's design and load considerations.