What is the definition of a horizontal ceiling?

A horizontal ceiling is defined as one that has a slope not exceeding 2 inches in 12 inches of horizontal run. This means that while there may be slight variations in the angle, any slope present is minimal and does not significantly alter the overall flatness of the ceiling. This definition is important for sprinkler fitting and other construction practices, where understanding the ceiling's characteristics can influence the installation of systems and compliance with safety standards.

In contrast, a ceiling that is completely flat and level would not be flexible in terms of construction standards, as very few ceilings are perfectly flat. A ceiling with an upward slope exceeding 2 inches in 12 inches indicates a non-horizontal surface that could complicate sprinkler system design and water distribution. Lastly, a ceiling that has various angles and slopes would also not conform to the definition of horizontal, as the term implies a consistency in minimal incline rather than multiple gradients.