For non-vehicular uses such as embankment stabilization, the maximum slope is determined by the angle of repose of the bedding sand, typically around 35 to 38 degrees. For vehicluar traffic, the highest slope in use is 18% (about 10 degrees) in a street in Colma, California. Special consideration is given to the drainage of the bedding sand at the bottom of the slope. Contact ICPI for details and guidance. Intermittent concrete header beams are generally not required.
Concrete headers typically used in paver crosswalks perform like bridge abutments. The pavement on aggregate base located on both sides of the header (in and outside the crosswalk) will deform at the junction of flexible pavement and rigid concrete. Why? Because there's no interlock between the aggregate base and the adjacent concrete. For that reason, most crosswalks should be placed on a concrete base with concrete headers separating the pavers from the adjacent pavement (typically asphalt).
Paver and bedding sand are considered as a single layer whose structural number is 0.44 per inch or 1.82 for 80 mm thick pavers and 25 mm of bedding sand. For more information on structural numbers, see the AASHTO guide for design of pavement structures.