What is the minimum slope required for a built-up roof?

The minimum slope required for a built-up roof is 1/4:12. This guideline is established to ensure proper drainage and to prevent water accumulation on the roof surface, which can lead to leaks and structural damage over time. A slope of 1/4:12 means that for every 12 horizontal inches, the roof rises a minimum of 1/4 inch. This slope is generally accepted as a standard to effectively channel water off the roof and discourage ponding.

If the slope were lower, such as 1/8:12, it may not provide sufficient drainage, increasing the risk of water pooling. Slopes greater than 1/4:12, while also effective, are not required for built-up roofs and may be excessive for certain design specifications, thus it is essential to adhere to the minimum guidelines provided by the North Carolina Residential Code.