AskCodeMan

Hi Jerry,

Duct penetration through the garage ceiling, required min. 26 gauge steel IRC 309.1.1.. Is rigid duct board acceptable material to penetrating the fire assembly?

Hi Richard,

First, the Florida Building Code, Residential has a similar requirement as the IRC for using 26 gage metal for that duct, however, duct board rated Class 0 or Class 1 IS a suitable alternative - however, the duct board would need to be labeled with such rating, otherwise I would write it up because the use of duct board is 'only allowed if rated Class 0 or Class 1'.

Third, that is not a "fire assembly", it is simply "separation".

From the Florida Building Code, Residential, with 2006 Revisions. (underlining and bold are mine)
- SECTION R309
- - GARAGES AND CARPORTS
- - - R309.1 Opening protection.
- - - - Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. Other openings between the garage and residence shall be equipped with solid wood doors not less than 13/8 inches (35 mm) in thickness, solid or honeycomb core steel doors not less than 13/8 inches (35 mm) thick, or 20-minute fire-rated doors.
- - - R309.1.1 Duct penetration.
- - - - Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be constructed of a minimum No. 26 gage (0.48 mm) sheet steel, 1-inch (25 mm) minimum rigid nonmetallic Class 0 or Class 1 duct board, or other approved material and shall have no openings into the garage.
- - - R309.2 Separation required.
- - - - The garage shall be separated from the residence and its attic area by not less than ½-inch (12.7 mm) gypsum board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than ½-inch (12.7 mm) gypsum board or equivalent.