Mineral-surfaced roll roofing must not be applied on decks with roof slopes below what ratio?

Mineral-surfaced roll roofing is typically not recommended for use on decks with slopes below a ratio of 1:12 due to the principles of water drainage and potential for moisture retention. The steepness of the slope is crucial because it affects how water is directed off the roof surface. A slope of 1:12 ensures that water drains away efficiently, reducing the likelihood of pooling, which can lead to leaks and damage.

At slopes below this ratio, the risk of water not running off effectively increases, which can cause premature deterioration of the roofing material. The specifics of roofing codes and manufacturer guidelines emphasize that lower slopes may require different types of roofing systems, such as built-up roofs or other materials designed for low-slope applications, to minimize the chances of water retention and associated problems.