Sheathing Requirements

[medeek]

I've got a pre-fab steel building, fully enclosed with a 6" slab foundation. Inside this building my client wants to frame up an interior space and insulate it however he wants to spend as little money as possible and does not want to apply sheathing to the interior walls (12' height) or to the TJI joists of the ceiling. Of course there will be some shearwalls for the seismic requirement, but other than that is there some code that requires full sheathing of the perimeter walls or can he just get away with putting up some fire retardent plastic over top of the insulation (I know doesn't sound like much of a structure to engineer). With the ceiling joists I'm basically of the opinion the whole diaphragm needs sheathing to get the appropriate diaphragm action out of it.

I had previously posted some related questions to this project but now I'm back to the drawing board since the client feels strongly that I've completely over engineered the (interior) structure.

A confused student is a good student.

 

[rn14]

In the case I mentioned there was only exterior sheathing. With the negative wind pressures the compression face is not braced so I assumed unbraced
for the entire length. That didn't work so I tried blocking at half then thirds. As far as what constitutes sufficient bracing, I know the steel manual
has a section (look up stability bracing) on it where they actually quantify strength and stiffness requirements but I'm not sure that I have seen
anything like it for timber.

 

[jayrod12]

Wood is a trick one for actually determining what is adequate blocking. It's not difficult to determine how often you need the blocking (i.e. 1/2 height, 1/3 heights etc.) but more difficult to know if the blocking will actually provide that lateral stability or will all the studs fail via buckling at the same time.

I say it is highly unlikely that each stud will buckle at the same time, and just as unlikely (or more so) that they'll all buckle the same direction.

 

[rn14]

Jayrod,take a look at TB-125. It is really short but they do mention global buckling of TJIs due to wind uplift forces.

 

[jayrod12]

Thanks for that rn14,

IT appears as though they say the TJIs could buckle as a unit when only provided with bottom chord bracing, and that they should provide full depth blocking at an intermittent spacing to transfer these loads to the roof diaphragm.

Wall blocking is full depth and as such I would tend to think meets the requirements of transferring the buckling load on the inside of the studs to the exterior diaphragm.

All that being said, medeek's case is unusual where he won't have any diaphragm to resolve the buckling forces into.