2019 California Standards for Accessible Design Guide (effective January 1, 2020 with July 1, 2021 amendments)

1132A.4.1 Thresholds.

Thresholds at the primary entry and required exit doors shall be no higher than ½ inch (12.7 mm). Thresholds at secondary exterior doors, including sliding door tracks, shall be no higher than ³/₄ inch (19.05 mm). Changes in height at interior door thresholds (e.g., floor material changes at door thresholds) shall not exceed ½ inch (12.7 mm). Thresholds shall comply with the following:

1. Thresholds with a change in height of not more than ¼ inch (6.35 mm) may be vertical. 

2. Thresholds with a change in height between ¼ inch (6.35 mm) and ³/₄ inch (19.05 mm) shall be beveled with a slope no greater than 1 unit vertical in 2 units horizontal (50-percent slope).