What type of force are roof ridges and rafters typically under?

Roof ridges and rafters are typically under compression forces. This is because the primary role of rafters is to support the roofing material and transfer loads down to the walls of the structure. When a load is applied, such as snow or the weight of roofing materials, the rafters tend to shorten and push down on the roof's ridge, creating a compressive force.

In a typical roof structure, as the rafters slope down from the ridge to the eaves, they are subjected to these compression forces as they work to hold up the entire roof system. The ridge board or ridge beam at the top of the roof acts as a key structural element to help maintain the shape and integrity of the roof by resisting the outward thrust of the rafters, further emphasizing the compressive nature of the forces involved.

Understanding the dynamics of these forces is essential for evaluating roof design and stability, ensuring that the materials and construction methods used can adequately support the loads they will encounter.