Final answer:
In building codes, the landing on each side of an exterior door should typically not exceed 1.5 inches below the threshold, with exceptions for sliding doors, doors that open onto ramps, and doors with powered operators.
Step-by-step explanation:
The question refers to building codes related to the construction of exterior door landings. In most building codes, the landing on each side of an exterior door should not be more than 1.5 inches (38 mm) below the top of the threshold. However, there are typically three exceptions to this rule:
- Where the exterior door is a sliding door,
- Where the door opens directly onto a ramp,
- Where a door is provided with a powered door operator.
These criteria ensure safety, accessibility, and ease of movement through an exterior doorway. The landing area ensures that there is enough space to move and provides a stable area to stand on while operating the door. These measures are critical for accommodating individuals with disabilities and ensuring safe egress in an emergency.