What is the critical factor for determining the maximum span of headers in exterior bearing walls?

The maximum span of headers in exterior bearing walls is primarily influenced by the ground snow load. Snow load considerations are critical because they determine the amount of weight that the structure must support. In areas with heavy snowfall, headers must be engineered to withstand not only the vertical loads from the building components above but also the additional loads imposed by accumulated snow.

While other factors like the width of the building, type of material used, and height of the wall do play roles in overall structural integrity, the ground snow load has a direct impact on how loads are distributed across the headers. Adequate consideration of this load ensures that the headers are appropriately sized and can provide the necessary support while maintaining structural safety and stability under various weather conditions.

Additionally, understanding snow load requirements helps inform other aspects of design, including the spacing of framing members and overall structural layout, which all work together to safely transfer loads to the foundation. Properly accounting for snow loads in the design process is essential for ensuring compliance with building codes and safety standards.