A purlin is a horizontal structural member used in roof construction. It supports the roof deck and helps distribute the weight of the roof to the vertical supports, such as walls or columns. Purlins are typically made from materials like steel or wood and are essential for maintaining the integrity of a building's roof structure. In a typical roofing system, purlins are placed at regular intervals along the length of the roof. They can be found in various types of buildings, including residential homes and commercial structures. Proper installation of purlins is crucial for ensuring the roof's durability and performance over time.