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Individual encasement for wood posts?

Y

Yikes

SAWHORSE
Joined
Nov 2, 2009
Messages
3,958
Location
Southern California
I have a 3 story Type V-A apartment building and at the second floor level there are some paralam beams resting on 6x6 wood posts buried inside a 1 hour wall.

The inspector says the wood post is a "column" and therefore must be individually encased with 1-hour protection per 704.2, as if it were a steel frame. I've had at least a dozen buildings plan-checked and built in this jurisdiction before, and this has never been an issue.

I'm thinking it's more like "integral elements in load bearing walls of light-frame construction" per 704.4.1 and therefore doesn't need additional layers of Type X inside the membrane protected wall.

Questions:

1. When discussing a structural frame, is there any substntive difference between naming something a "post" vs. column? (I tend to thinkof a post as integral to the wall, whereas a column is a freestanding element, but this cpuld be an irrelevant distinction).

2. When 704.4.1 mentions "boundary elements", what does that mean? Exterior walls? Or any wall (exterior or interior) that defines the "boundary" of a room? Or is it the "boundary" of a shear panel?
 
My first reaction: The column is protected inside the 1 hour wall. Additional protection (wrapping the other sides of the column) would be redundant. T601 requires 1 hour protection which is accomplished in the one hour wall separating the column from the interior.

After researching: Still the same but the section on boundary elements seems to muddy the water a bit. Boundary elements are essentially jacks, kings and other normal parts of a framed wall that support wall loads but aren't considered "columns" within the wall. So boundary elements are not considered "columns". And boundary elements can be protected by the wall (without separate protection). This implies that if an element is considered a column, it would need independant protection. Still, though it is a little out of my expertise I fail to see a strong connection.
 
I guess the question is, if you have a load bearing wall in a building that has to have fire rating applied to structural elements do you wrap the studs, or rate the wall. Of course you rate the wall. wrapping the studs would be crazy. Wrapping a column that is completely embedded in a wall that has a fire resistance that meets or exceeds that required by the column would be fine if you wanted to do it. Requiring it would be crazy.

The more I think about this the angrier I get. The intent of the section is to provide 1 hour from the start of fire to the potential of structural failure of the building to allow egress and to extinguish the fire. The intent is being met. This is foolish.
 
tmurray: The structural walls already are 1-hour rated in a Type V-A, so that's not an either/or option (membrane protection vs. individual protection). The question was, is additional individual encasement required inside the already-rated membrane wall?

In other words, everywhere I have a 6x6 wood post or column, do I need to add a 5 1/2" wide layer of 5/8" X on each side of the post?

I say "no", but I agree with Sifu that the wording of the code is murky.

Think of it another way: 704.2 requires continuous column protection when a column penetrates through a ceiling. But in "Western Platform" wood frame construction, the 6x6 posts stop underneath the top plates of the wall. So, was the intent of the code to think of a "column" as being something more independent of the wall than just an extra-thick stud (post)? If "yes" then my 6x6 post should not be considered a "column".
 
This usually becomes an issue when the floor framing extends beyond the exterior walls to create a balcony....... if the wood post are supporting a gravity load of a floor or roof above and are exposed, the inspector may be right....... especially if the balconies are covered by a roof section above. in other words, if the building can be structurally stable and support all wind, water, and seismic loads without the exterior 6X6 posts, then they may not need to be protected. Another option is to use alternate means and methods where the designer shows that enough sacrificial wood is in place to allow the exposed wood columns to support the loads for one hour as required by type VA construction.
 
I'm out of the office and don't have a code handy, but I've been hit by this before. The membrane protection of a rated wall isn't adequate. You need 5/8" fire-rated gypsum board on the sides of the column (or post) embedded in the wall, or to increase the sizes as Builder Bob suggested.

Maintaining fire-rated membrane continuity in VA construction can be a nightmare.
 
Yikes said:
tmurray: The structural walls already are 1-hour rated in a Type V-A, so that's not an either/or option (membrane protection vs. individual protection). The question was, is additional individual encasement required inside the already-rated membrane wall?In other words, everywhere I have a 6x6 wood post or column, do I need to add a 5 1/2" wide layer of 5/8" X on each side of the post?

I say "no", but I agree with Sifu that the wording of the code is murky.

Think of it another way: 704.2 requires continuous column protection when a column penetrates through a ceiling. But in "Western Platform" wood frame construction, the 6x6 posts stop underneath the top plates of the wall. So, was the intent of the code to think of a "column" as being something more independent of the wall than just an extra-thick stud (post)? If "yes" then my 6x6 post should not be considered a "column".
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Sorry, I don't use ICC codes, so most of this is Latin to me. Our code would require the 1 hour wall to be wrapped around any openings to maintain rating and does not stipulate where the separation occurs for structural members as long as the structural member is separated from the floor area, so the construction you explained is compliant. The only additional thing that might be required to be rated would be the member used to continue the load within the floor system.

I guess what I was getting at is wording of the code is irrelevant. Intent is what matters. The intent of this section, if similar to our code, is; "To limit the probability that floor assemblies exposed to fire will prematurely fail or collapse, which could lead to the spread of fire from a lower storey of a building to an upper storey or to the exterior of the building during the time required to achieve occupant safety and for emergency responders to perform their duties, which could lead to harm to persons." the intent appears to have been met. The wonderful thisng about our code is that it not only tells you what you have to do, but why you have to do it. It makes interpreting the code much easier.
 
Builder Bob said:
This usually becomes an issue when the floor framing extends beyond the exterior walls to create a balcony....... if the wood post are supporting a gravity load of a floor or roof above and are exposed, the inspector may be right....... especially if the balconies are covered by a roof section above. in other words, if the building can be structurally stable and support all wind, water, and seismic loads without the exterior 6X6 posts, then they may not need to be protected. Another option is to use alternate means and methods where the designer shows that enough sacrificial wood is in place to allow the exposed wood columns to support the loads for one hour as required by type VA construction.
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BB, there is no exterior condition in the building I'm describing. Everything is interior, and all posts are within walls.

What's happening is that the apartments on the upper floors are located over an open office and mail room on other (non-stacking) walls on the first floor. The posts are inside those walls.
 
Couldn't the wall be framed with 6x6 studs? It is not the typical method but certainly exceeds the minimum stud size requirement. In this particular condition it sounds as if the 6x6 is in place to provide vertical load transfer like blocking would and that this is a matter of semantics. Replace the post with 3 gang nailed studs. A column typically handles both vertical and lateral forces, has positive connections to a footing and beam or structural system above. The fact that the beam is pocketed into the wall to sit specifically on the post rather than resting on a "boundary element" of the wall (the top plate) seems to be the issue. I wouldn't consider the post a column but it could be a primary structural member and certainly would be a secondary structural member which has the exception for conventional light frame construction.

Also the boundary elements are all of the components of a rated wall at its' perimeter or at the perimeter of an opening in that rated wall. Top plates, king studs at door or window openings, bottom plates and end studs of a wall would all be the boundary elements. The code section elaborates presumably because at some point an overzealous inspector extrapolated that the drywall continuity should "be continuous" and completely encase the wall framing even over and below the plates and wrap all openings or something similar.

Hope that helps,

ZIG
 
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