509.4.2 Protection.

Where Table 509 permits an automatic sprinkler system without a fire barrier, the incidental uses shall be separated from the remainder of the building by construction capable of resisting the passage of smoke. The walls shall extend from the top of the foundation or floor assembly below to the underside of the ceiling that is a component of a fire-resistance-rated floor assembly or roof assembly above or to the underside of the floor or roof sheathing, deck or slab above. Doors shall be self- or automatic-closing upon detection of smoke in accordance with Section 716.5.9.3. Doors shall not have air transfer openings and shall not be undercut in excess of the clearance permitted in accordance with NFPA 80. Walls surrounding the incidental use shall not have air transfer openings unless provided with smoke dampers in accordance with Section 710.8.

509.4.2.1 Protection limitation.

Except as specified in Table 509 for certain incidental uses, where an automatic sprinkler system is provided in accordance with Table 509, only the space occupied by the incidental use need be equipped with such a system.

Section BC 510: Special Provisions

510.1 General.

The provisions in Sections 510.2 through 510.10 shall permit the use of special conditions that are exempt from, or modify, the specific requirements of this chapter regarding the allowable building heights and areas of buildings based on the occupancy classification and type of construction, provided the special condition complies with the provisions specified in this section for such condition and other applicable requirements of this code. The provisions of Sections 510.2 through 510.8 are to be considered independent and separate from each other.

(Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023)

Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.

510.2 Horizontal building separation allowance.

Buildings shall be considered as separate and distinct from each other for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction, where all of the following conditions are met:

   1.   The buildings are separated with a horizontal floor assembly having a fire-resistance rating of not less than 3 hours.

   2.   The building below the horizontal assembly is of Type IA construction.

   3.   Shaft, stairway, ramp or escalator enclosures through the horizontal floor assembly shall have not less than a 2-hour fire-resistance rating with opening protectives in accordance with Section 716.5.

      Exception: Where the enclosure walls below the horizontal floor assembly have not less than a 3-hour fire-resistance rating with opening protectives in accordance with Section 716.5, the enclosure walls extending above the horizontal floor assembly shall be permitted to have a 1-hour fire-resistance rating, provided:

         1.   The building above the horizontal floor assembly is not required to be of Type I construction;

         2.   The enclosure connects fewer than four stories; and

         3.   The enclosure opening protectives above the horizontal floor assembly have a fire protection rating of not less than 1 hour.

   4.   The building or buildings above the horizontal assembly shall be permitted to have multiple Group A occupancy uses, each with an occupant load of less than 300, or Group B, M, R or S occupancies.

   5.   The building below the horizontal assembly shall be protected throughout by an approved automatic sprinkler system in accordance with Section 903.3.1.1, and shall be permitted to be any occupancy allowed by this code except Group H.

   6.   The maximum building height in feet (mm) as measured from the grade plane shall not exceed the limits set forth in Section 504.3 for the building having the smaller allowable height as measured from the grade plane.

(Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023)

Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.