What is the maximum rainfall that the drains on a sloped roof can handle?

The maximum rainfall that drains on a sloped roof can handle is established based on engineering standards and practices that account for various factors including the type of roofing, the design of the drainage system, and regional rain patterns. In many building codes, a figure of 6 inches per hour is often used as a standard capacity for roof drainage systems to ensure that they can efficiently manage heavy precipitation.

This figure is significant because it allows for the potential of intense rainstorms which can occur unexpectedly. Designing a drainage system to accommodate up to 6 inches of rainfall per hour helps prevent water accumulation on the roof, which could lead to leaks, structural damage, and in some cases, roof collapse. Moreover, it ensures that the excess water is effectively directed away from the building foundation and reduces the risk of flooding around the property.

While some roofs may be designed to handle lower rates of rainfall, the 6 inches per hour standard is considered a practical benchmark that most drainage systems are built to meet, particularly in areas susceptible to heavy rainfall.