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High challenge (HC) fire walls shall meet the requirements of this chapter and Chapter 4 except as modified by this chapter.
HC fire walls shall be designed and constructed to remain stable after the collapse of the structure due to fire on either side of the wall.
HC fire walls constructed in compliance with the requirements of Sections 5.3, 5.4, or 5.5 shall be deemed to provide the required stability.
HC fire walls shall be nonbearing.
Structural framing within the plane of the wall shall be permitted to be load-bearing.
Cantilevered HC fire walls shall be entirely self-supported and nonbearing.
There shall be no connections to the building(s) or contents on either side other than to the flashing.
Cantilevered HC fire walls shall be erected where there is a complete break in the structural framework.
Tied HC fire walls shall be centered on a single column line or constructed between a double column line and shall be limited to one-story buildings.
Structural framing on either side of the wall shall line up horizontally and vertically and shall support the roof.
The framework on each side of the HC fire wall shall be continuous or tied together through the wall.
The framework on each side shall be designed so that it resists the maximum lateral pull that can be developed due to framework collapse in a fire on the opposite side.
Tied HC fire walls shall be supported laterally by the building framework with flexible anchors.
Where centered on a single column line, structural framing at the column line shall have a fire resistance rating of not less than the required fire resistance rating of the HC fire wall.
Where the wall is installed between double column lines, structural framing along the first column line immediately on each side of the HC fire wall shall have a fire resistance rating of not less than the required fire resistance rating of the HC fire wall.
A double HC fire wall shall consist of two parallel walls.
There shall be no connections, other than to the flashing, between the walls.
Each wall that comprises a double HC fire wall shall be supported laterally by the building frame on its respective side and shall be independent of the other wall and framing on the opposite side.
Where the roofs on opposite sides of an HC fire wall are not at the same elevation, the HC fire wall assembly shall be arranged as described in either 5.6.1 or 5.6.2.
The two buildings shall be separated by a double HC fire wall, with each wall extending from the foundation to above the roof of its respective building to form a parapet.
A cantilevered HC fire wall shall be continuous from the foundation to the top of the parapet for the lower roof.
The upper wall shall be supported by the framework of the higher building and shall be structurally independent of the cantilevered HC fire wall.
The upper wall section shall be permitted to have an exterior fire resistance rating of 1 hour less than the required fire resistance rating of the lower cantilevered portion but not less than a 2-hour rating.
Clearance to allow for expansion of unprotected structural framework shall be provided between cantilevered HC fire walls and structural framework on both sides and between double HC fire walls.
In buildings assigned to Seismic Design Category C, Seismic Design Category D, Seismic Design Category E, or Seismic Design Category F, as determined in accordance with ASCE/SEI 7, Minimum Design Loads for Buildings and Other Structures, sufficient separation shall be provided between cantilevered HC fire walls and adjacent framing on each side and between double HC fire walls to allow independent movements of the elements without contact.
The total width of all openings in HC fire walls shall not exceed 25 percent of the length of the wall in each story.
Single opening protectives in HC fire walls shall not exceed the maximum size tested.
HC fire walls shall have each opening protected with two fire door assemblies.
Openings in double HC fire walls shall be protected in accordance with 5.8.4.1 or 5.8.4.2.
One fire door shall be provided in each respective wall.
Two fire doors shall be required within a vestibule, where the vestibule has a fire resistance rating greater than or equal to that required for the double HC fire wall.
Where material handling systems penetrate an HC fire wall, the system design shall provide a method to stop the material handling system and allow fire doors to close without obstruction.
Penetrations of HC fire walls shall only be permitted in accordance with Section 5.9.
Unless permitted by 5.9.4, penetrations shall be positioned to pass through the wall no more than 36 in. (915 mm) above the finished floor level.
A steel sleeve of a size to allow an approximate 1 in. (25 mm) clearance between the sleeve and the penetrating item shall be provided.
The space between the sleeve and penetrating item (annular space) shall be filled as required in Section 4.9.
Joint reinforcement shall be provided in the horizontal mortar joints immediately above and below sleeves in concrete masonry walls, and all hollow spaces of concrete masonry walls immediately adjacent to the sleeve shall be filled with concrete, mortar, or grout.
The clear space between the openings for the penetrating items shall be not less than 3 times the largest dimension of the largest opening.
The limitation on the height of penetrations above the floor and other requirements of Section 5.9 shall not apply where the structural framework of the building has a fire resistance rating equal to or greater than the required fire resistance rating of the HC fire wall; only compliance with Section 4.9 shall be required.
Piping conveying high-hazard materials shall be in accordance with Section 5.11.
Fire dampers shall be installed and maintained in accordance with NFPA 80, Standard for Fire Doors and Other Opening Protectives.
HC fire walls shall be protected with two fire damper assemblies.
For double HC fire walls, each wall assembly shall be protected with a fire damper rated for that wall with a slip joint connecting the sleeves between the HC fire walls.
For cantilevered and tied HC fire walls a slip joint connecting the sleeves shall be provided on both sides of the two dampers to separate the ductwork on each side from the section containing the dampers.
Ductwork conveying high-hazard materials shall be in accordance with Section 5.11.
Piping or ductwork that is used to convey high-hazard materials shall not penetrate HC fire walls that have a required fire resistance rating of 4 hours or greater.
Piping or ductwork that is used to convey high-hazard materials and that penetrates fire walls with a required fire resistance rating of less than 4 hours shall be protected with approved devices or with systems designed to terminate the flow or movement of the materials through the fire wall automatically upon fire detection.
HC fire walls shall extend from the foundation to a point at least 30 in. (760 mm) above the top surface of the roof being protected.
Roofs sloped greater than 1/4 in. per foot (6 mm per 305 mm) downward toward the HC fire wall shall be provided with a minimum 36 in. (915 mm) parapet.
HC fire walls shall be permitted to terminate at or above the top surface of the roof deck, provided the structural framework (columns, beams, and girders) one bay out on both sides of the HC fire wall has the same fire resistance rating as the HC fire wall.
Roof surfaces adjacent to the HC fire wall for at least 25 ft (7620 mm) on each side shall be constructed and protected in accordance with 5.13.1 through 5.13.2.2.3.
For buildings less than or equal to 60 ft (18 m) in height and located outside hurricane prone regions, as defined by ASCE/SEI 7, Minimum Design Loads for Buildings and Other Structures, the roof surface adjacent to HC fire walls for at least 25 ft (7620 mm) on each side shall be protected in accordance with 5.13.1.1 or 5.13.1.2.
For single-ply membranes, gravel ballast or concrete paver blocks shall provide complete membrane coverage and shall be installed in accordance with ANSI/SPRI RP-4, Wind Design Standard for Ballasted Single-Ply Roofing Systems.
Built-up and modified bitumen roofs shall be surfaced with gravel or slag applied at a minimum rate of 4 lb/ft2 (19 kg/m2) and embedded in a flood coat of hot asphalt or coal-tar.
For buildings greater than 60 ft (18 m) in height or located within hurricane prone regions, as defined by ASCE/SEI 7, Minimum Design Loads for Buildings and Other Structures, the roof surface on each side of the roof adjacent to HC fire walls for at least 25 ft (7620 mm) on each side shall be protected in accordance with 5.13.2.1 or 5.13.2.2.
For single-ply membranes, concrete paver blocks shall provide complete membrane coverage and shall be installed in accordance with ANSI/SPRI RP-4, Wind Design Standard for Ballasted Single-Ply Roofing Systems.
Built-up and modified bitumen roofs adjacent to HC fire walls shall be surfaced with gravel or slag embedded in a flood coat of hot asphalt or coal-tar and applied at a minimum rate of 4 lb/ft2 (19 kg/m2).
Gravel or slag shall be embedded into a double flood coat of hot asphalt or coal-tar to ensure full embedment.
After cooling, any loose gravel or slag shall be removed from the roof.
All graveled roofs greater than 60 ft (18 m) in height shall have a minimum parapet height of 24 in. (610 mm).
Roof structures with combustible construction or contents, such as monitors, penthouses, or cooling towers, not more than 20 ft (6100 mm) in height above the roof shall be located at least 50 ft (15 m) from HC fire walls required to have a fire resistance rating exceeding 2 hours.
Roof structures with combustible construction or contents over 20 ft (6100 mm) in height shall be provided with a separation distance not less than 21/2 times the height of the roof structure from HC fire walls.
Heat and smoke vents, skylights, and unprotected roof penetrations for air-handling equipment or smoke control systems shall be located at least 25 ft (7620 mm) from HC fire walls requiring a fire resistance rating of more than 2 hours and at least 48 in. (1220 mm) from HC fire walls requiring a fire resistance rating of 2 hours or less.
HC fire walls shall comply with the requirements of 5.16.2 through 5.16.3.
The length and arrangement of end walls shall be in accordance with Table 5.16.2.1 and Figure 5.16.2.1(a) or Figure 5.16.2.1(b).
Table 5.16.2.1 Wall Protection
Height of Exposing Area
 
Length of End Wall
ft
m
 
ft
mm
≤40
≤12.2
 
6
1830
41-70
12.5-21
 
10
3050
≥71
≥21.6
 
14
4265
Note: Protection should consist of blank, fire-rated construction.

FIGURE 5.16.2.1(a) End Wall Exposure Protection — End Walls Tied to Structural Framing.


FIGURE 5.16.2.1(b) End Wall Exposure Protection — End Walls Not Tied to Structural Framing.
The fire resistance rating of the end walls shall be based on fire exposure from the outside and shall be a minimum of 1 hour, or 2 hours less than that of the HC fire wall, whichever is greater.
For light hazard and ordinary hazard (Group 1 or 2) occupancies as defined in NFPA 13, Standard for the Installation of Sprinkler Systems, in lieu of providing end walls, the fire wall shall be permitted to extend to a distance of at least 30 in. (760 mm) beyond the exterior face of the exterior walls, as shown in Figure 5.16.2.3.

FIGURE 5.16.2.3 End Wall Exposure Protection for Light Hazard and Ordinary Hazard (Group 1 or 2) Occupancies.
Openings for truck docks and railroad sidings shall not be located within 20 ft (6100 mm) on either side of an HC fire wall.
The length of fire-resistive angle walls, Y, as shown in Figure 5.16.3.1, shall be 35 ft (10.7 m).

FIGURE 5.16.3.1 Angle Wall Exposure Protection.
The fire resistance rating of the angle walls shall be based on fire exposure from the outside and shall be 1 hour, or 1 hour less than that of the HC fire wall, whichever is greater.
Construction of each wall and eave shall be noncombustible for an additional 65 ft (20 m) beyond the fire resistance-rated construction.
Elevation differences perpendicular to HC fire walls shall be protected as angle walls, as shown in Figure 5.16.3.4.
FIGURE 5.16.3.4 Exterior Wall Protection.