How many trimmer and header rafters are required when framing around an opening in the ceiling with a header span exceeding 4?

When framing around an opening in the ceiling, particularly when there is a header span exceeding four feet, it is essential to ensure that the structural integrity is maintained. In this scenario, two trimmer rafters are required to support the header that spans the opening. Each trimmer rafter runs vertically from the ceiling to the header and provides the necessary support for the weight above the opening, distributing loads effectively to maintain the stability of the structure.

Additionally, when framing, it's standard practice to place the header between these trimmer rafters, eventually connecting the rafters to the existing rafters in the ceiling. This configuration creates a framework that can adequately bear the loads from the roof, ceiling, and anything else that may be placed on or above the header.

By requiring two trimmer rafters, the structural system ensures that the header is properly supported on both sides, mitigating the risk of sagging or failure over time, which is crucial when the header span exceeds four feet.