Ballasted Low-Slope Roof Systems1504.4 Ballasted low-slope roof systems. Ballasted low-slope (roof slope < 2:12) single-ply roof system coverings installed in accordance with Section 1507 shall be designed in accordance with Section 1504.8 and ANSI/SPRI RP-4.
Code InterpretationThis code implies that single ply low-slope roof systems only qualify for ballasted applications if they meet the wind requirements set forth in Section 1504.8. This section is quite explicit in stating that structures located in hurricane zones and/or high wind exposure areas shall not receive ballasted applications.
The exact section is as follows: “Section 1504.8. Gravel and stone. Gravel or stone shall not be used on a roof of a building located in a hurricane-prone region as defined in Section 1609.2, or any other building with a mean roof height exceeding that permitted by Table 1504.8 based on the exposure category and basic wind speed at the building site.”
In addition, the designer should check with the building owner’s insurance company to determine if loose-laid ballasted systems are acceptable. Some insurance carriers - such as FM - do not approve of loose-laid ballasted systems in any wind regions.