What is the minimum height above the roof plane for skylights set at an angle of less than 45 degrees?

The minimum height above the roof plane for skylights set at an angle of less than 45 degrees is established to ensure proper water drainage and to minimize the risk of water pooling around the skylight. Setting a minimum height of 4 inches is necessary to create a proper slope for runoff, which helps to mitigate potential leaks and water intrusion into the building. This height allows for effective management of water on the roof surface, particularly in areas with significant precipitation.

Choosing a height that is too low could lead to a situation where water accumulates, increasing the risk of roof damage and ceiling leaks. With a minimum height of 4 inches, building codes aim to enhance the longevity of the skylight installation and maintain the structural integrity of the roofing system. The other options represent heights that may not adequately prevent such issues, therefore making 4 inches the most practical and code-compliant choice for skylights placed at this angle.