2012 IBC - Shafts, Ductwork and Damper requirements

[Scott_R]

Project: Renovation of a y.1915 Dormitory structure with following criteria:

Steel structure, masonry exterior bearing wall, clay tile (fire resistance) less than 3,000 sf per floor

4 stories plus basement. Adding NFPA13 fire suppression.

First floor toilet rooms need exhaust fans that cannot exit through roof. We are running duct work along ceiling and into a vertical chase DOWN to mechanical room at basement. From there will be a direct exhaust through exterior wall. The mechanical room is rated for one-hour ceiling and walls.

Question 1: Does the chase above need to be rated? I know in 2006-9 IBC it does not if shaft is 2 story or less and floor/ceiling has a damper on the exhaust duct. I can't find this in the 2012 IBC anywhere.

Question 2: If it does need rating (1 hour) - can I have the damper at the in the horizontal floor location only leading onto mechanical room (basement) and not at the top and bottom of shaft?

Thanks!

Scott

 

[Mr. Inspector]

607.6 Horizontal assemblies.

Penetrations by air ducts of a floor, floor/ceiling assembly or the ceiling membrane of a roof/ceiling assembly shall be protected by a shaft enclosure that complies with Section 713 and Sections 717.6.1 through 717.6.3 of the International Building Code or shall comply with Sections 607.6.1 through 607.6.3.

607.6.1 Through penetrations.

In occupancies other than Groups I-2 and I-3, a duct constructed of approved materials in accordance with Section 603 that penetrates a fire-resistance-rated floor/ceiling assembly that connects not more than two stories is permitted without shaft enclosure protection provided that a listed fire damper is installed at the floor line or the duct is protected in accordance with Section 714.4 of the International Building Code. For air transfer openings, see Exception 7, Section 712.1.8 of the International Building Code.

Exception: A duct is permitted to penetrate three floors or less without a fire damper at each floor provided it meets all of the following requirements.

1. The duct shall be contained and located within the cavity of a wall and shall be constructed of steel having a minimum thickness of 0.0187 inch (0.4712 mm) (No. 26 gage).

2. The duct shall open into only one dwelling unit or sleeping unit and the duct system shall be continuous from the unit to the exterior of the building.

3. The duct shall not exceed 4-inch (102 mm) nominal diameter and the total area of such ducts shall not exceed 100 square inches for any 100 square feet (64 516 mm2 per 9.3 m2) of the floor area.

4. The annular space around the duct is protected with materials that prevent the passage of flame and hot gases sufficient to ignite cotton waste when subjected to ASTM E 119 or UL 263 time-temperature conditions under a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water at the location of the penetration for the time period equivalent to the fire-resistance rating of the construction penetrated.

5. Grille openings located in a ceiling of a fire-resistance-rated floor/ceiling or roof/ceiling assembly shall be protected with a listed ceiling radiation damper installed in accordance with Section 607.6.2.1.

 

[mtlogcabin]

Since it is an existing building you should start with the Existing Building Code

IEBC 2012

1012.7.3 Other vertical shafts.

Interior vertical shafts other than stairways, including but not limited to elevator hoistways and service and utility shafts, shall be enclosed as required by the International Building Code when there is a change of use to a higher hazard category as specified in Table 1012.4.

Exceptions:

1. Existing 1-hour interior shaft enclosures shall be accepted where a higher rating is required.

2. Vertical openings, other than stairways, in buildings of other than Group I occupancy and connecting less than six stories shall not be required to be enclosed if the entire building is provided with an approved automatic sprinkler system.

And in case you did not adopt the IEBC the IBC still authorizes its use

3401.6 Alternative compliance.

Work performed in accordance with the International Existing Building Code shall be deemed to comply with the provisions of this chapter.