Concealed Vertical Spaces

Robert Autrey · 10-24-2009, 11:46 AM

Yesterday I encountered a furdown above a triangular area framed in a corner of a hallway. Below, in the hallway, the area is sheathed with drywall with inset drywall shelves for art display. In the attic, however, there is a hole about 2-1/2 feet deep. Shouldn't this vertical space be firestopped at the ceiling level, or does the waferboard sheathing preclude the need for a ceiling level firestop?

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Robert Autrey · 10-24-2009, 11:52 AM

Similarly, at the same house, the draft stop (or fireblocking) at the vertical chimney chase has been penetrated at two locations. One is a CATV cable that descends from the attic through a hole that appears to have been bored by the home owner in order to mount a flat panel TV above the fireplace opening. The hole is rather large and the code indicates to me that some kind of fitting is needed to provide closure at the gap. The hole seen in the attached photo penetrates the top of the stud wall that forms the face of the fireplace (and one side of the triangular flue chase). Nearby, and directly adjacent to the fireplace flue itself, is a 4-inch flex duct that penetrates the draftstop at the ceiling level. There is also about a 1/2-inch gap at that penetration. Should these penetrations have some type of fitting as seems to be indicate in the code?

**Jerry Peck** · 10-24-2009, 07:12 PM

Originally Posted by Robert Autrey

Shouldn't this vertical space be firestopped at the ceiling level,

Correct, that should be fireblocked at the ceiling level.

or does the waferboard sheathing preclude the need for a ceiling level firestop?

Nope.

**Jerry Peck** · 10-24-2009, 07:14 PM

Originally Posted by Robert Autrey

The hole is rather large and the code indicates to me that some kind of fitting is needed to provide closure at the gap.

Should these penetrations have some type of fitting as seems to be indicate in the code?

Those need to be sealed around, yes.

**Wayne Carlisle** · 10-26-2009, 09:04 AM

In my opinion the furdown above the triangular area framed in a corner of the hallway does have the proper fireblocking.

Now the penetrations where the wires are need sealed.

**Bruce Breedlove** · 10-26-2009, 12:33 PM

Also, don't ignore the energy losses in the uninsulated walls of those furdowns. A simple solution is to cover the top of the box (with something like plywood or OSB), seal the joints (to reduce air infiltration) and insulate over it.

**paul hardy** · 10-26-2009, 04:54 PM

you will also note that most fireplace manufactures require the the fresh air intake opening to be lower than the top of the fire box that one appears to go up the chimney,

Robert Autrey · 10-26-2009, 06:29 PM

Originally Posted by paul hardy

you will also note that most fireplace manufactures require the the fresh air intake opening to be lower than the top of the fire box that one appears to go up the chimney,

While I didn't thoroughly trace the flex flue it did have a louvered type backflow damper on the exterior and I'm pretty sure it was the discharge from the master bathroom vent fan.

**Jerry Peck** · 10-26-2009, 06:42 PM

Originally Posted by Wayne Carlisle

In my opinion the furdown above the triangular area framed in a corner of the hallway does have the proper fireblocking.

I guess it is just me, but my gut tells me that structural panel does not meet the 3/4" ( 23/32" ) minimum thickness ... I mean, how many jobs have ANY 3/4" structural panels on them?

See R602.8.1 in the IRC.

**Wayne Carlisle** · 10-27-2009, 11:43 AM

Originally Posted by Jerry Peck

I guess it is just me, but my gut tells me that structural panel does not meet the 3/4" ( 23/32" ) minimum thickness ... I mean, how many jobs have ANY 3/4" structural panels on them?

See R602.8.1 in the IRC.

Originally Posted by Robert Autrey

Below, in the hallway, the area is sheathed with drywall

It sounds to me like it is already fireblocked and does not need any additional fireblocking.

1

/2-inch (12.7 mm) gypsum board is allowed as fireblocking.

**Jerry Peck** · 10-27-2009, 12:47 PM

Originally Posted by Wayne Carlisle

It sounds to me like it is already fireblocked and does not need any additional fireblocking.

1/2-inch (12.7 mm) gypsum board is allowed as fireblocking.

Correct.

You are allowed to use 1/2" gypsum board, but you are not allowed to use 1/2" structural panel - the structural panel would need to be 3/4" - and structural panel is what is shown, not gypsum board.

Or cover that exposed structural panel with 1/2" drywall, that would work.