Fire-rated parapet required? CBC 704.11

[Yikes]

I'm a California guy, still getting used to the IBC. I have a new "flat-roofed" building with exterior wall parapets to aid in directing the roof drainage and aesthetics (to hide some rooftop equipment). The building is type V-A wood-framed apartments (one-hour construction). The parapet is NOT used as a fire wall, it is atop the exterior walls, and per CBC/IBC 704.11 exc. #1 a parapet is not required due to location on property.

QUESTION: If I'm not required to provide a parapet for code reasons, but I provide one anyway for aesthetic reasons, does the parapet still have to be one-hour rated? (e.g. per CBC 704.11.1)

The plan checker is making me sheath the back side of the parapet with Type X gyp board over my plywood sheathing before applying the modified bitument roofing up the wall. I would rather not put gyp board here.

 

[High Desert]

Re: Fire-rated parapet required? CBC 704.11

If it's not required to be rated per the exception, I don't see how they can make you rate it. That's why Oregon has the "write and cite" rule. Did you ask them why they thought it had to be rated?

 

[Yikes]

Re: Fire-rated parapet required? CBC 704.11

I think the problem is once I use the word "parapet", the plan checker feels compelled to go to 704.11.1.

What else should I call it? A "vertical apputenance"? A "non-rated, non-code required parapet"?

 

[Gene Boecker]

Re: Fire-rated parapet required? CBC 704.11

Is the wall required to have a rating per Table 602? If so, the plan reviewer may be arguing that the parapet is an extension of the wall (it's vertical, you know) and therefore needs a rating.

 

[Yikes]

Re: Fire-rated parapet required? CBC 704.11

Gene, per table 602 I am welll over 30' away from any property line.

Per table 601 my exterior walls are required to be one-hour rated, but I also meet the parapet exception listed in 704.11 item #4.

I think I just need to go back and request a change to the approved plans based on these comments.

 

[Gene Boecker]

Re: Fire-rated parapet required? CBC 704.11

Well then, Yikes.

As my kids were find of saying, I am a man without a clue.

 

[MarkRandall]

Re: Fire-rated parapet required? CBC 704.11

Interest one. I see your point for non-rating the parapet, but I also see the reasoning for the building official to ask for one hour. Once you build the parapet, IMHO, it becomes part of the exterior wall and would require one hour rating.

I just read 704.11 and the first sentance says: "Parapets shall have the same fire-resistance rating as that required for the supporting wall." Therefore even on second thought, I still agree with plans reviewer. If you build it, it shall be rated the same as the wall. The exception is only for not building it.

 

[Glennman CBO]

Re: Fire-rated parapet required? CBC 704.11

MarkRandal,

I would say you are correct. it may not be a parapet technically, but it is a wall. If the exterior wall is required to be rated, the parapet (or the top portion of the wall) needs the same rating.

 

[JBI]

Re: Fire-rated parapet required? CBC 704.11

Yikes - I'm going with the group on this one, it is indeed part of the wall.

Not at all unlike the 'triangle' on a gabled building of otherwise type III construction. If that triangle was framed with wood, sheathed with plywood, your otherwise type III building becomes type V, woodframed. The logic in that case is driven by firefighter safety during an event. If the woodframed gable end fell outward in a collapse it could easily imperil responders at the scene. If on the other hand it were built of CMU, like the rest of the wall beneath it, there is less liklihood of endangering the man with the big hose.

I could easily make the same point/argument about your non-parapet wall extension. Could you slope the extension to resemble a hipped roof? That may be a part of a solution.

 

[Yikes]

Re: Fire-rated parapet required? CBC 704.11

John, I can understand what you are saying, except that I think of this aesthetic parapet as a component tht is outside of the building envelope. So when I test-drive that logic on other components outside the building envelope - such as combustible cornices, eaves and projections - then 704.2.3 would allow me to build it without a fire-resistance rating. So why is it that a horizontal eave or cornice (which projects outward and is thus more likely to have flame burning underneath it, and to fall on people below) IS allowed to be unrated, but a vertical parapet that has 7/8" stucco on one side and class A modified bitumen roofing on the other must also have gyp board on the bitumen side?

Also, if 704.5 would allow me to build an exterior wall that is only fire-rated for fire exposure from the INSIDE, and on a parapet wall there is no such thing as an "inside", then can't I omit the fire rating altogether?

The reason I ask is because I've built - and seen others build - dozens of wood-framed commercial buildings with non-code-required parapets over the years, and most of the time the fire protection envelope terminated at the roof-ceiling assembly. The back of the parapet usually had a plywood substrate on it, and the roof had a cant strip and a torch-down modified bitument face that ran up the backside of the parapet, without an extra layers of gyp board over the plywood. Were we all wrong on this for all those years?

 

[High Desert]

Re: Fire-rated parapet required? CBC 704.11

I am going to agree with yikes on this. I think that requiring the parapet to be rated is a little bit of an anal interpretation of the code. A rated parapet is to control fire spread to an adjacent structure, not to maintain the fire-resistance of the wall below it. If I understand the O.P., the walls are rated because of Table 601 and not Table 602. What would the benefit of rating the parapet be? A literal reading of the code? They could have eave projections and unlimited unprotected openings in the exterior walls but if they put a parapet on the building for aesthetics or to screen rooftop equipment, they have to rate it? Sorry, but the logic escapes me on this one.