Fire Stop

The Dryerbox has been classified by Underwriters Laboratories, Inc. for models 350, 425, 480, 3D, and 4D for use in Through-Penetration Underwriters Laboratories Through Penetration Firestop System Firestop System Number W-L-7129.

UL Classifieds Underwriters Laboratories Certifications Directory reference numbers: XHGK.R21933 (US), XHGK7.R21933 (CANADA) and XHEZ.W-L-7129 (FIRESTOP SYSTEM). Cabinets For Use in Penetration Firestop Systems See UL Fire Resistance Directory <25XC>

Firestop System Number W-L-7129

Click here for a direct link to UL's online specifications for firestop system installation.
Click here for the Dryerbox Classification Listing (for Canada, here).

Quick One-Hour Wall Firestop Instruction Summary

UL Report These key components are noted on the instruction sheet that comes with every Dryerbox. The following are highlights to comply with the UL Classification for through-penetration firestop systems. To achieve a fire resistance rating (one-hour F & T) 2X6 framing is required. The Dryerbox unit must be installed in accordance with the UL Cabinet System listing.

Drywall requirements: An extra layer of type-X drywall must be installed in the ID of the stud cavity in which the Dryerbox is located. Drywall must be attached to nailers (minimum 1" X 2") located on the inside of the cavity wall studs. Secure nailers to wall framing at max 18 in. OC. The screws used to attach the inner layer of drywall shall be spaced a maximum of 18 inches apart.

UL Labs Certification and Firestop Configuration for One Hour Wall

Studs and Insulation requirements - see table below.
Dryerbox Models Wall Studs Summary
350, 425, 3D and 4D Wood See Note 1
350, 425, 3D and 4D Steel See Note 2
480 Steel and Wood See Note 3
 

Note 1: The entire depth of stud cavity with Dryerbox® must be filled with R19 fiberglass batt insulation. Additional insulation shall be added within the cavity as necessary to completely fill all voids around the periphery of the Dryerbox and around the dryer vent pipe.

Note 2: The entire wall cavity containing the cabinet shall be tightly packed to full stud depth and cavity height with mineral wool batt insulation having a min density of 4 pcf. In addition, the wall stud cavities immediately adjacent to the cavity with the cabinet shall be insulated with min R13 glass fiber batt insulation (or min 4 pcf mineral wool batt material) for the full depth and height of the stud cavity.

Firestop Print Summary

2012 International Building Code Guidance

Please Note that Local Amendments May Vary

IBC 708.3  (709.3 in prior code) - Requirements When Sprinkler Systems are Included

Current building code only requires a 1/2 hour rating for Dryerbox® installation when used in conjunction with a sprinkler system. You may find the full, relevant code excerpt below. To achieve a half hour rating, you only need to build out using Firestop System Configuration A Wall Assembly Components which are even simpler. (1 Hour Rating Requires Configuration B as outlined above)

708.3 Fire-resistance rating. Fire partitions shall have a fire-resistance rating of not less than 1 hour.
Exceptions:
  1. Corridor walls permitted to have a 1/2 hour fire-resistance rating by Table 1018.1.
  2. Dwelling unit and sleeping unit separations in buildings of Type IIB, IIIB and VB construction shall have fire-resistance ratings of not less than 1/2 hour in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.

SECTION 1018 CORRIDORS

1018.1 Construction.

Corridors shall be fire-resistance rated in accordance with Table 1018.1. The corridor walls required to be fire-resistance rated shall comply with Section 708 for fire partitions.

Exceptions:
  1. A fire-resistance rating is not required for corridors in an occupancy in Group E where each room that is used for instruction has at least one door opening directly to the exterior and rooms for assembly purposes have at least one-half of the required means of egress doors opening directly to the exterior. Exterior doors specified in this exception are required to be at ground level.
  2. A fire-resistance rating is not required for corridors contained within a dwelling or sleeping unit in an occupancy in Group R.
  3. A fire-resistance rating is not required for corridors in open parking garages.
  4. A fire-resistance rating is not required for corridors in an occupancy in Group B which is a space requiring only a single means of egress complying with Section 1015.1.
  5. Corridors adjacent to the exterior walls of buildings shall be permitted to have unprotected openings on unrated exterior walls where unrated walls are permitted by Table 602 and unprotected openings are permitted by Table 705.8.

TABLE 1018.1 CORRIDOR FIRE-RESISTANCE RATING

Occupancy Occupant Load Served by Corridor Without sprinkler system With sprinkler systemc
H-1, H-2, H-3 All Not Permitted 1
H-4, H-5 Greater than 30 Not Permitted 1
A, B, E, F, M, S, U Greater than 30 1 0
R Greater than 10 Not Permitted 0.5
I-2a, I-4 All Not Permitted 0
I-1, I-3 All Not Permitted 1b
 
  1. For requirements for occupancies in Group I-2, see Sections 407.2 and 407.3.
  2. For a reduction in the fire-resistance rating for occupancies in Group I-3, see Section 408.8.
  3. Buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 where allowed.

Additional Firestopping Details

You may find ancillary white papers and engineering letters on the Architects & Engineers pages in addition to the engineering letters below that detail back to back installation options.

  • Back to Back Installation for 1 Hour Walls
    2006 Code Engineering specifications for installing the Dryerbox in both sides of a one hour fireresistance rated wall assembly.
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  • Back to Back Installation for 1 Hour Walls
    2009 Code Engineering specifications for installing the Dryerbox in both sides of a one hour fireresistance rated wall assembly.
    Download PDF