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exposed wood in a soffit

Vlab20

Vlab20

Bronze Member
Joined
Mar 11, 2010
Messages
89
Location
Midwest
I have a A-2 occupancy and a 5A class of construction. The building is also fully sprinklered NFPA 13. The code is International Building Code (IBC)I have a drywall soffit that was built up against a 1-hour rated wall and up against a 1-hour rated floor ceiling assenbly. My ceiling is a dropped acoustical ceiling that intersects my soffit. Above the acoustical ceiling at the face of the soffit my drywall stops and thus exposes the wood studs above the acoustical ceiling. See attached sketch.Fire marshal has requested that drywall be placed inside the wood framed soffit and along the outside face of the soffit. The fire marshal did not cite a code section and we are trying to get that from him but we could not find a code section that supports the fire marshal's position.Anyone know what code section this may fall in?

View attachment 1732

exposed wood soffit-optimized.pdf

exposed wood soffit-optimized.pdf
 
Agree Nfpa 13 is driving it

But there are means to not Sheetrock

Concealed combustible spaces have to have sprinkler protection or meet what use to be called the exceptions

If the fire sprinkler company is good they should know

Section reference depends on which edition is adopted

Is it that much sheet rock that is needed???
 
There are multiple soffits throughout the building that would fall into the category that the sketch is portraying. Plus the request to drywall "inside" the soffit presents a head scratcher as to how this is done. I will crack open NFPA 13 to investigate...Thanks for the lead.
 
Just looked at NFPA 13...we are already providing a sprinkler head inside of the soffit space. The Fire Marshal is requesting that we ALSO provide drywall around the wood soffit members both inside and outside. It is the issue of covering the wood studs that has me perplexed. Thoughts?
 
Without seeing the whole cow, I could see requiring it on the outside only, to prevent spread above the act, unless that area is sprinkled

Once again if the sprinkler company is any good they should be a me to assist in what needs to be done

Also there is a means in Nfpa 13 for sprinkling when there are limited combustibles

Not in the office this week or I could give you that section
 
In my opinion you just have to cover or block the possible spread of fire and do not have to provide a rate assembly unless it is part of one

So plain old sheet rock
 
= =

From the 2010 Edition of NFPA 13, Section 8.15.1.3 - Concealed Space

Design Requirements: Sprinklers in concealed spaces having no access

for storage or other use shall be installed in accordance with the

requirements for light hazard occupancy.

= =
 
= =

Referring to your drawing, IMO, it seems that if a sprinkler head is

installed in each of the concealed soffitt areas you describe and

butts up against 1 hr. rated assemblies on the vertical & horizontal

planes, ...that additional gyp. board would not be required.

I would respectfully continue requesting the code section from the

Fire Marshall.



= =
 
What happens to the coverage that the sprinkler provided?

I see it mentioned below that there are no sprinkler heads between the hard lid and the acoustic tile ceiling. Apparently the heads are there for the soffit and only the soffit. That seems like a strange way to do this.

I recall seeing heads above the t-bar a bunch of times.

Another thing I wonder about is the sprinkler heads, don't they need to be accessible for inspection and service?

Don't mind me....the fire dept handles this stuff for us.
 
Last edited by a moderator:
north star said:
= =From the 2010 Edition of NFPA 13, Section 8.15.1.3 - Concealed Space

Design Requirements: Sprinklers in concealed spaces having no access

for storage or other use shall be installed in accordance with the

requirements for light hazard occupancy.

= =
Click to expand...
There is another section saying something like if you have a small amount if combustibles, you do not have to sprinkle the entire area

Basically one head might do it
 
Problem is wood construction fire sprinkled buildings are basically penalized in that most if the wood has to have sprinkler protection

I have no problem with the call but only think one layer is needed on the outside to prevent spread, if there was a fire, over the act ceiling.
 
= =

I cannot see the requirement for additional gyp. board, especially since

the sprinkler head is already in the concealed space, AND butts up

against rated assemblies.....How much potential propogation is there

going to be because of the design in the drawing?....Sprinkled AND

rated assemblies! :o Plus, there is that conundrum of how to

construct the soffits.......I wonder if stuffing each concealed space

with "mineral wool" [ non-flammable insulation ] would satisfy the

Fire Marshall, ..."IF" it is even required.

Hopefully, **Vlab20** will let us know the outcome.

= =
 
Yes one option in 13 is to fill a void space "completely" with non combustible insulation

I do not agree with all codes / standards but if the void spaces are not protected per 13, than the system does not meet 13

And if there ever was a fire, inspector and fire sprinkler company will have to answer why not

So do it correctly the first time
 
Hum.....three layers of drywall and a sprinkler? Should'nt there be a fire stop or block between the wall studs before the soffit starts? Would be a little difficult to tape and mud the inside of that soffit would'nt it?

Any can lights in the soffit? ventilation requirement?

pc1
 
It is all Nfpa 13 driven issue

Seems like just need a barrier to seal from the combustible construction to the un sprinkled non combustible area above the act ceiling area

Like if you are in some mall lease space storage area and the wall between the storage area and retail dies not go to the deck. And, there are no sprinklers above the retail drop ceiling area.

A fire in the storage area can progress and go up and over into the area above the non sprinkled drop ceiling area.

Same principle just bigger area
 
Is it simply a fireblocking issue? 2009 IBC 717.2.3 Fireblocking shall be provided at interconnections between condealed vertical stud call or partition spaces and concealed horizontal spaces such as occur at soffits, drop ceilings, (etc.).

We require them to either sheetrock all the way to the top plate, or, provide blocking between the studs at the drop ceiling line, or, fill the stud bays with insulation, as they would for sound.
 
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