Answer :
Final answer:
Purlins are horizontal supporting structures in roof construction, typically made as 2x4 or 2x6 timber pieces. These nominal sizes refer to their cross-sectional dimensions and are standard due to their strength and practicality.
Explanation:
Purlins are horizontal structural members used in roof construction. They are typically made from wood and serve as support for the roof deck, roof cladding, or other structural components such as rafters or trusses. Common dimensions for purlins when made of wood would be either 2x4 (which refers to 2 inches by 4 inches in cross-sectional dimensions) or 2x6 (2 inches by 6 inches). These measurements are nominal sizes, which means the actual size is slightly less due to the finishing process. These sizes are quite standard as they provide an optimal balance between strength, cost, and ease of handling.
