- If a registered architect or engineer has certified that the adjacent roof assembly provides a fire rating no less than that required for the exterior wall of the proposed building or a 1- hour rating, whichever is greater, and that the roof is not used for storage, the 12-foot vertical separation required above may be reduced to 3 feet (914 mm). Where there are skylights or other openings in the adjacent roof that are less than 10 feet (3048 mm) from the exterior wall of the opposing building, the percentage of openings allowed in Section 705.8 shall be as follows:
- 0 to 3 feet separation between buildings: 0 percent.
- 3 to 5 feet separation between buildings: 15 percent.
- 5 to 10 feet separation between buildings: 25 percent.
- If a registered professional engineer has submitted a written report of inspection certifying that the adjacent building is protected throughout with a fire sprinkler system conforming to Section 903, the 12-foot (3658 mm) vertical separation required above may be reduced to 3 feet (914 mm).
|R = (Rn0.59 + pl )1.7||(Equation 7-9)|
|R||=||The fire-resistance rating of the assembly (hours).|
|Rn||=||The fire-resistance rating of the individual wall (hours).|
|pl||=||Coefficient for thickness of plaster.|
Values for Rn0.59 for use in Equation 7-9 are given in Table 722.4.1(3). Coefficients for thickness of plaster shall be selected from Table 722.4.1(4) based on the actual thickness of plaster applied to the wall or partition and whether one or two sides of the wall are plastered.