What minimum percentage of the wall surface must solid headers comprise?

The minimum percentage of the wall surface that solid headers must comprise is 4%. This requirement is primarily to ensure structural integrity and support. Solid headers are essential components that carry loads above doorways and windows, distributing the weight of the structure evenly to prevent sagging or failure. By specifying that solid headers must make up at least 4% of the wall surface, the code ensures that there is adequate material to support the loads resisting lateral forces, such as wind or seismic activities. This requirement also helps maintain the overall stability and durability of the building, especially in areas where wall openings compromise the wall's structural load-bearing capacity.

Other percentages specified in the choices do not meet the minimum criteria set forth in the building codes, as they would not provide sufficient support for the structural elements above openings within the wall.