Sloping Roofs – Members that directly support the covering material In roof framing terminology, which members primarily support the roof covering (such as sheets or tiles) on a sloping roof, taking loads between rafters and transferring them to the main frame?

Introduction / Context:Understanding the load path in pitched roofs helps with design, detailing, and economical material use. Covering materials require immediate support at regular spacing and that support, in turn, sits on a larger primary framework. This question distinguishes between primary inclined members and secondary longitudinal members beneath the covering.

Given Data / Assumptions:

• Sloping roof framed with principal rafters/common rafters.
• Covering may be corrugated sheets laid on purlins or tiles laid on battens fixed to purlins.
• Conventional timber or steel roof practice.

Concept / Approach:

Purlins are longitudinal members spanning between trusses or frames and directly supporting sheeting; for tiled roofs, battens are nailed to the purlins and support individual tiles. Rafters are the main inclined members that carry purlins/battens. Struts and collar ties are bracing members controlling buckling and spreading, not direct supports for covering.

Step-by-Step Solution:

Verification / Alternative check:

Standard details show sheet fixings to purlins with specified spacing; tile battens are first fixed to purlins or rafters.

Why Other Options Are Wrong:

Rafters support purlins, not sheets directly in typical systems; battens support tiles but are subordinate to purlins; struts/collar ties are bracing elements.

Common Pitfalls:

Confusing tile battens with purlins; assuming covering is always fixed to rafters without an intermediate system.

Final Answer:

Purlins