40 Hour Property and Building Inspection Practice Test

How do knee walls and purlins differ in their function?

1. Knee walls support rafters and purlins run along the rafters

2. Purlins support ceilings and knee walls support roofs

3. Knee walls are vertical and purlins are horizontal

4. They serve the same purpose

The correct answer is: Knee walls support rafters and purlins run along the rafters

Knee walls and purlins have distinct roles in a structural system, particularly in roof construction. Knee walls are short, vertical walls that typically support the ends of rafters, especially in a building's attic space or in areas with sloped roofs. Their function is crucial in transferring loads from the roof down to the foundational structure, thereby providing additional support and stability. By connecting the rafters to the floor or ceiling framework, knee walls help in maintaining the integrity of the roof structure. Purlins, on the other hand, are horizontal members that run perpendicular to the rafters and provide support for sheathing or roofing materials. They distribute loads from the roof sheeting to the rafters and help create a more stable structure. By running along the rafters, they enhance the strength of the roof system and allow for efficient load transfer. The differentiation in their functions highlights the complementary roles that knee walls and purlins play in ensuring the safety and stability of a building's roof. Understanding these roles is essential for anyone involved in property and building inspection as it provides insight into structural integrity and the importance of proper construction practices.