NCBC 713.12 Shaft Enclosure Top

[jrharvey]

Hi Everyone,

Project is a 3 story, NFPA 13R sprinkled, Construction Type VB, R-2 Apartment in North Carolina. 5 total units sharing 1 stair. The stair is an exterior stair. During plan review the AHJ is saying this is a stair shaft and needs to be treated as such. We have a 1 hour fire barrier separating the stair from the dwelling units. The entire roof of the building is a 1 hour rated roof per UL P531. When plans were submitted I showed the 1 hour fire barrier stopping at the 1 hour rated roof. The AHJ is saying this doesn't meet code. They are saying the fire barrier is required to go through the 1 hour roof assembly to the deck above or a completely separate, structurally independent, horizontal shaft wall needs to be installed underneath the already rated 1 hour roof. They say only a horizontal shaft wall would meet 713.12. So a 1 hour rated horizontal shaft wall directly below the 1 hour roof. I may be wrong but I cannot find any justification for this in the code at all. I also checked the IBC commentary which doesnt address any of this that I can find. It may be there and Im just not seeing it. Whats most concerning is in my entire career doing multifamily I have not seen a horizontal shaft wall ever below a stair in a situation like this. AHJ cannot cite a code section regarding this, just saying its their policy and interpretation of the code. I’m trying to gauge if I am completely wrong here or if they are. Attaching some sketches to help.

I know some people may say its not worth to fight but its completely halted the project. The way things are designed the fire barrier cannot be extended to the roof without wood truss penetrations and the structural engineer says they cant really make it work hanging the trusses off the fire barrier. The issue witht he horizontal shaft wall is the AHJs requirement to be structurally supported by the shaft wall and not be attached to the roof above in any way.

Any help would be very appreciated.

 

[steveray]

Fire barriers used to read that way, but now they let you terminate at a "lid"....Which technically I don't agree with in a wood framed 13R, but it doesn't matter what I like....Maybe they are misreading #2?

​

713.12 Enclosure at Top​

The top of shaft enclosures shall comply with one of the following:

1. Extend to the underside of the roof sheathing, deck or slab of the building, and the roof assembly shall comply with the requirements for the type of construction as specified in Table 601.
2. Terminate below the roof assembly and be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.
3. Extend past the roof assembly and comply with the requirements of Section 1511.

And Welcome to THE forum.....

 

[jrharvey]

Fire barriers used to read that way, but now they let you terminate at a "lid"....Which technically I don't agree with in a wood framed 13R, but it doesn't matter what I like....Maybe they are misreading #2?

​

713.12 Enclosure at Top​

The top of shaft enclosures shall comply with one of the following:

1. Extend to the underside of the roof sheathing, deck or slab of the building, and the roof assembly shall comply with the requirements for the type of construction as specified in Table 601.
2. Terminate below the roof assembly and be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.
3. Extend past the roof assembly and comply with the requirements of Section 1511.

And Welcome to THE forum.....

Thank you very much for the response. I guess the main question is whether or not there's anything in the code that requires the lid to be a completely structurally independent and separate assembly from the rest of the building. Is this something assumed and not just mentioned in the code or am I missing something? Do you think the AHJ is just wrong here?

 

[jrharvey]

This is what NCBC says which is basically the same...

713.12 Enclosure at Top​

A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.

Personally I do think that they are misreading but they are saying that I am the one misreading and misunderstanding the code. Im just not sure who exactly is right. I mean I think I am the one that is right but I always want to verify with others.

 

[steveray]

To me....you are correct.....
But I could see someone arguing that the vertical rating needs to terminate BELOW the roof rating and have it's own separate lid.....

Terminate below the roof assembly and be enclosed at the top with construction of the same fire-resistance rating

The issue in my opinion is that you can have a wood 13R attic with no detection and no suppression and when a fire breaks out in that light frame attic, it all collapses into the stairwells and no one gets out...But hey, it hasn't happened yet so it must not be a problem...

 

[Yankee Chronicler]

jrharvey, in discussing this with the AHJ (or with us) I think you need to have your terminology correct. In your opening post you wrote, "The entire roof of the building is a 1 hour rated roof per UL P531."

I have never heard of a 1-hour rated roof, and I'm pretty certain that UL Design P531 is a 1-hour rated roof-ceiling assembly. Just as most UL designs for rated horizontal separations between stories are floor-ceiling assemblies, the same holds true for roof-ceiling assemblies. Which is to say that what many people (including far too many architects) refer to and think of as a "rated ceiling" is NOT a rated ceiling. The ceiling is only the bottom membrane of a rated assembly. And, looking up Design P531 on the UL Product IQ web site, that's what Design P531 is -- a roof-ceiling assembly.



Then we look at the code. You have the correct code section -- sort of:

713.12 Enclosure at Top. A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.

The UL Design P531 is a 1-hour rated roof-ceiling assembly, so the code does allow you to terminate the shaft enclosure walls against the underside of the rated roof-ceiling assembly. It's worth noting that the model ICC 2021 IBC section 713.12 offers three options for termination, of which #2 is the one that uses the language in your NC code.

2. Terminate below the roof assembly and be enclosed at
the top with construction of the same fire-resistance
rating as the topmost floor penetrated by the shaft, but
not less than the fire-resistance rating required for the
shaft enclosure.

The 2021 IBC Commentary says the following about option #2:

The second condition requires that two minimum
fire-resistance ratings be checked (that of the upper-
most floor penetrated by the shaft and that of the shaft
itself) and that the most restrictive be applied.

As noted, there are very few actual fire-resistance rated ceilings. Likewise, there are very few (if any) fire-resistance rated floors. Most are rated floor-ceiling assemblies. So when the code talks about the fire-resistance rating of the topmost floor being penetrated by the shaft, what it's really talking about is the rated floor-ceiling assembly. What's the rating of the third story floor-ceiling assembly? If it's zero or 1-hour, then all you need to close the top of the exit enclosure is a 1-hour roof-ceiling assembly. And that's what UL Design P531 is.

HOWEVER -- you also wrote that the exit stair is an exterior exit stair. How many sides of the stair are open? Getting down to basics, if it is an exterior exit stair, it is NOT an exit [stair] enclosure, so it's not a shaft. If it's not a shaft, section 713.12 does not apply. If the exit stair is an exterior exit stair, you (and the code official) need to be looking at whatever provisions apply to separating exterior exit stairs from the interior of the building.

 

[Yankee Chronicler]

Continuing: If what you have is, in fact, an exterior exit stair, then the following apply (from the NC code, as it appears in UpCodes):

1027.6 Exterior Exit Stairway and Ramp Protection. Exterior exit stairways and ramps shall be separated from the interior of the building as required in Section 1023.2. Openings shall be limited to those necessary for egress from normally occupied spaces. Where a vertical plane projecting from the edge of an exterior exit stairway or ramp and landings is exposed by other parts of the building at an angle of less than 180 degrees (3.14 rad), the exterior wall shall be rated in accordance with Section 1023.7.

This brings us to:

1023.2. Construction. Enclosures for interior exit stairways and ramps shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both. Interior exit stairway and ramp enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more and not less than 1 hour where connecting less than four stories. The number of stories connected by the interior exit stairways or ramps shall include any basements, but not any mezzanines. Interior exit stairways and ramps shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.

Section 707 would apply to the wall(s) separating the stair from the interior. Section 711 would address the roof-ceiling assembly overhead of the stair. The language is "assemblies," and UL Design P531 is a rated assembly.

 

[jrharvey]

jrharvey, in discussing this with the AHJ (or with us) I think you need to have your terminology correct. In your opening post you wrote, "The entire roof of the building is a 1 hour rated roof per UL P531."

I have never heard of a 1-hour rated roof, and I'm pretty certain that UL Design P531 is a 1-hour rated roof-ceiling assembly. Just as most UL designs for rated horizontal separations between stories are floor-ceiling assemblies, the same holds true for roof-ceiling assemblies. Which is to say that what many people (including far too many architects) refer to and think of as a "rated ceiling" is NOT a rated ceiling. The ceiling is only the bottom membrane of a rated assembly. And, looking up Design P531 on the UL Product IQ web site, that's what Design P531 is -- a roof-ceiling assembly.

View attachment 14133

Then we look at the code. You have the correct code section -- sort of:



The UL Design P531 is a 1-hour rated roof-ceiling assembly, so the code does allow you to terminate the shaft enclosure walls against the underside of the rated roof-ceiling assembly. It's worth noting that the model ICC 2021 IBC section 713.12 offers three options for termination, of which #2 is the one that uses the language in your NC code.



The 2021 IBC Commentary says the following about option #2:



As noted, there are very few actual fire-resistance rated ceilings. Likewise, there are very few (if any) fire-resistance rated floors. Most are rated floor-ceiling assemblies. So when the code talks about the fire-resistance rating of the topmost floor being penetrated by the shaft, what it's really talking about is the rated floor-ceiling assembly. What's the rating of the third story floor-ceiling assembly? If it's zero or 1-hour, then all you need to close the top of the exit enclosure is a 1-hour roof-ceiling assembly. And that's what UL Design P531 is.

HOWEVER -- you also wrote that the exit stair is an exterior exit stair. How many sides of the stair are open? Getting down to basics, if it is an exterior exit stair, it is NOT an exit [stair] enclosure, so it's not a shaft. If it's not a shaft, section 713.12 does not apply. If the exit stair is an exterior exit stair, you (and the code official) need to be looking at whatever provisions apply to separating exterior exit stairs from the interior of the building.

Thank you for the reply. I agree with the terminology comment. Sorry, I sometiems get in a rush just trying to get the idea out but I agree its a roof/ceiling assembly. The stair is open on 3 sides. Im attaching a floor plan for reference. I agree this is not a shaft but the AHJ insist it must be treated as a shaft for the top since since 1027.6 leads you to 1023.2 which leads you to 707 and 707.5 for continuity which finally leads you to 713.12 for the enclosure at top. Theres also some disagreement between the reviewers and the state on whether the corridor requires a fire barrier for a shaft or a fire partition for a corridor. The local AHJ is taking the stance its better to consider the inside corridor as part of the stair and rate it as a fire barrier.

I 100% agree the code requires the fire barrier to end at a rated assembly and P531 is a rated assembly. The AHJ is just arguing that 707.5 requires fire barriers to continue through the ceiling and to the roof deck OR it must have an enclosure top that is a completely separate, self supporting assembly thats rated at the top and bottom to work.

Sounds like, based on what I am hearing here and everywhere else a fire barrier is allowed to stop at the top of a horizontal rated assembly per 711. I thought maybe there was some understanding of section 707.5 or 713.12 that I couldnt see or didnt know that would justify what the AHJ is saying but it doesnt sound like there is.

Thank you.

 

[Yankee Chronicler]

Ain't no way, no how, that's a shaft. That is clearly an exterior exit stair. Section 713 does not apply, section 711 does apply.

 

[redeyedfly]

Thank you for the reply. I agree with the terminology comment. Sorry, I sometiems get in a rush just trying to get the idea out but I agree its a roof/ceiling assembly. The stair is open on 3 sides. Im attaching a floor plan for reference. I agree this is not a shaft but the AHJ insist it must be treated as a shaft for the top since since 1027.6 leads you to 1023.2 which leads you to 707 and 707.5 for continuity which finally leads you to 713.12 for the enclosure at top. Theres also some disagreement between the reviewers and the state on whether the corridor requires a fire barrier for a shaft or a fire partition for a corridor. The local AHJ is taking the stance its better to consider the inside corridor as part of the stair and rate it as a fire barrier.

I 100% agree the code requires the fire barrier to end at a rated assembly and P531 is a rated assembly. The AHJ is just arguing that 707.5 requires fire barriers to continue through the ceiling and to the roof deck OR it must have an enclosure top that is a completely separate, self supporting assembly thats rated at the top and bottom to work.

Sounds like, based on what I am hearing here and everywhere else a fire barrier is allowed to stop at the top of a horizontal rated assembly per 711. I thought maybe there was some understanding of section 707.5 or 713.12 that I couldnt see or didnt know that would justify what the AHJ is saying but it doesnt sound like there is.

Thank you.

Wow, your AHJ is not competent.

No way this is a shaft. What horizontal assemblies are you penetrating?? This is 1027 Exterior Exit Stairways and Ramps, I mean, it's right in the title of the section!!

 

[jrharvey]

Wow, your AHJ is not competent.

No way this is a shaft. What horizontal assemblies are you penetrating?? This is 1027 Exterior Exit Stairways and Ramps, I mean, it's right in the title of the section!!

Yes 100% agree but 1027 tells you to have a rated separation per 1023. 1023 tells you it must be fire barriers per 707. 707.5 tells you the walls must go to roof deck or end at a rated assembly per 713.12. Its a little weird but its the correct path I think. The biggest part of the argument with them is whether or not a roof/ceiling assembly UL P531 meets the intent of 713.12. The AHJ says it does not and just yesterday admitted there is nothing in the code, nothing from ICC or our state (NCDOI) that has this requirement. They basically said this is their opinion and if I disagree I will have to go through their formal appeal which could take roughly a month and a half to 2 months. Basically they know they are not correct now and basically saying they dont care and they will punish the client with delays if we want to pursue anything.

 

[redeyedfly]

Is this Mecklenburg County?

Yes 100% agree but 1027 tells you to have a rated separation per 1023. 1023 tells you it must be fire barriers per 707. 707.5 tells you the walls must go to roof deck or end at a rated assembly per 713.12. Its a little weird but its the correct path I think. The biggest part of the argument with them is whether or not a roof/ceiling assembly UL P531 meets the intent of 713.12. The AHJ says it does not and just yesterday admitted there is nothing in the code, nothing from ICC or our state (NCDOI) that has this requirement. They basically said this is their opinion and if I disagree I will have to go through their formal appeal which could take roughly a month and a half to 2 months. Basically they know they are not correct now and basically saying they dont care and they will punish the client with delays if we want to pursue anything.

You could have just said you were in Mecklenburg County

 

[Yankee Chronicler]

The AHJ says it does not and just yesterday admitted there is nothing in the code, nothing from ICC or our state (NCDOI) that has this requirement. They basically said this is their opinion and if I disagree I will have to go through their formal appeal which could take roughly a month and a half to 2 months. Basically they know they are not correct now and basically saying they dont care and they will punish the client with delays if we want to pursue anything.

I have been in this situation as an architect. It's the client's choice. You can explain to your client that other code professionals agree the AHJ is incorrect, but ultimately if the client prefers to spend the extra money rather than wait for the appeal process to play out -- it's their choice.

I have to say, it's extremely disappointing to see a code official play the punish-the-applicant game rather than admit they've made a mistake. None of us are perfect. I've made wrong calls, and when the applicant can show me that the code supports their position, I accept it and I figure I learned something new that day. Our job (collectively) is supposed to be to enforce the code, not to see who's the biggest dog on the junkyard.

 

[jrharvey]

Is this Mecklenburg County?

You could have just said you were in Mecklenburg County

Your familiar with Mecklenburg? Ive had to appeal 4 times now in Mecklenburg and all 4 times NCDOI decided that Mecklenburgs interpretation was incorrect.

 

[Sifu]

Are we sure you can use the lid at all? 707.5 base code requires the fire barrier continuity to extend to the roof sheathing, not a rated horizontal assembly. The use of a rated horizontal assembly appears to be limited to shaft enclosures and interior exit stairways. I can't say it is a stretch to allow the rated horizontal assembly or that it makes sense from an intent point of view, just that the precise language may not support it. Plus, by using the rated roof/ceiling assembly we are trying to protect the stair below the assembly from a fire above, and I question whether that assembly is designed to provide this protection as it seems it is intended to protect the attic from a fire below.

But two rated assemblies really seems like a stretch!

This is close to home right now as I have the same condition where I noted that they had to extend to the underside of the roof sheathing, but in this case they were not proposing a rated lid over the exterior stairway anyway.

However.....Is the separation above the stairway needed at all? The exit stairway is required to be protected from fires within the adjacent unit, which is encapsulated by the rated exterior wall and the required rated assembly at the ceiling. So the stair is isolated from the interior fire. Unless that fire starts in the attic, but as stated, is that assembly designed to provide protection from above? Note that nothing in 1027 speaks to the top of the exterior stair. Maybe this is not needed if the code intends that the the isolation is assumed by use of the fire barrier continuity?

 

[steveray]

Are we sure you can use the lid at all? 707.5 base code requires the fire barrier continuity to extend to the roof sheathing, not a rated horizontal assembly.

Not anymore....

 

[jrharvey]

Are we sure you can use the lid at all? 707.5 base code requires the fire barrier continuity to extend to the roof sheathing, not a rated horizontal assembly. The use of a rated horizontal assembly appears to be limited to shaft enclosures and interior exit stairways.

Both me and the local AHJ read section 1027 for exterior exit stairs to treat fire separation as if its an interior exit stair. So any limitations or exceptions for interior also apply to exterior. Thats our understanding of the code. The conflict just comes into play when we talk about what section 713.12 actually looks like in real life as constructed.

I will say after a LONG discussion back and forth with everyone at the county the one issue everyone including the reviewer missed was that section 711.2.3 exception #2 does not apply to the stairs therefore making this design non compliant due to me also using that exception to not rate the load bearing walls that support the roof. Type VB does allow the load bearing walls to not be rated for dwelling units but doesnt say anything about stairs so in this particular case the stair would require the roof to be fully supported by a rated assembly. Now I still think in a type VA construction the stair still meets the word of the code but thats not what I have.

 

[Sifu]

I missed the other inclusion as I was looking at the '18. New information, question still applies...unless my postulation that it isn't needed at all is applicable.

I do see the path for the lid exception. 1027.6 refers us to 1023.2 for the construction/ratings. 1023.2 refers us to 707 for fire barriers. 707.5 excepts the continuity by sending us back to 1023.2 which allows the lid via a horizontal assembly, as well as 713.12. A circuitous path to be sure and open to some confusion, at least on my part because we do not have an enclosure. I took the 1027.6 reference to 1023.2 as applying only to the walls since there is no mention of the ceiling since it is not an enclosure, but I see that may be open to interpretation.

 

[steveray]

I missed the other inclusion as I was looking at the '18. New information, question still applies...unless my postulation that it isn't needed at all is applicable.

I do see the path for the lid exception. 1027.6 refers us to 1023.2 for the construction/ratings. 1023.2 refers us to 707 for fire barriers. 707.5 excepts the continuity by sending us back to 1023.2 which allows the lid via a horizontal assembly, as well as 713.12. A circuitous path to be sure and open to some confusion, at least on my part because we do not have an enclosure. I took the 1027.6 reference to 1023.2 as applying only to the walls since there is no mention of the ceiling since it is not an enclosure, but I see that may be open to interpretation.

Hate how all of that got reconfigured and the lumping of exit enclosures in with shafts....Shafts have stuff, exits have people...They are not the same....

 

[Yankee Chronicler]

Hate how all of that got reconfigured and the lumping of exit enclosures in with shafts....Shafts have stuff, exits have people...They are not the same....

Especially since an exterior exit stair isn't in a shaft and isn't enclosed. "Enclosure" is not required for an exterior exit stair. What is required is separation between the stair and the interior of the building.