Why are sloped roofs not considered waterproof?

Sloped roofs are designed to shed water rather than hold it. This means that the architecture and materials used in sloped roofing facilitate the drainage of rainwater away from the roof surface and into gutters or directly off the edges of the roof. The purpose of this design is to prevent water from accumulating, which could lead to leaks, structural damage, and other water-related issues.

While sloped roofs can effectively manage water runoff, they are not considered waterproof because there is always a possibility of water infiltration, especially in areas where materials meet or around penetrations such as vents and chimneys. Unlike completely flat roofs that might hold water and require more robust waterproofing measures, sloped roofs manage water flow but are still susceptible to leaks if not properly maintained or installed.

In essence, the design objective is to effectively direct and remove water rather than to create an impermeable barrier, which clarifies why sloped roofs are not classified as waterproof.