What is the role of purlins in roof construction?

Purlins play a crucial role in roof construction by providing horizontal support for rafters. They effectively reduce the span of the rafters, which means they help distribute the load more evenly across the roof structure. By reducing the effective length of the rafters, purlins enhance the overall stability and strength of the roof. This structural support helps prevent sagging and potential failure under various loads, including snow and wind.

Purlins are typically installed perpendicular to the rafters and can be made of wood or metal, depending on the requirements of the building. This use significantly contributes to the integrity and longevity of the roof system. In contrast, other options like supporting ceiling joists, attaching wall coverings, or providing insulation do not accurately describe the primary function of purlins in roof construction.