# Brittle finishes



## rktect 1 (Dec 8, 2010)

I am looking at an interior 1 hour rated partition wall between two tenant spaces.  The plans added a note that prior to construction, this wall would be "designed" by company X.  I have yet to see these plans and we are going to inspect the rough framing today.  The wall is floor to deck at +/- 35' tall.  So I went to look up the deflection limits on the 2006 IBC table 1604.3.  On this table there is listed either brittle finish or flexible finish.  So I was wondering where in this code it give me the manner in determining what is brittle and what is flexible.

Is 5/8" type X drywall brittle?  Is it even a finish, maybe not?  If it is, I don't see how this wall can be constructed with anything other than 8" steel studs for limitng heights assuming 5psf.

Any thoughts.

And I am not trying to design this wall, just trying to understand it enough to either accept or deny it.


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## brudgers (Dec 8, 2010)

Gypsum board is not brittle. Hold a sheet horizontally and notice that it deflects without breaking.

Other than in a traction elevator shaft, horizontal deflection for interior partitions is rarely an issue, because there is rarely a source of horizontal loading.


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## fatboy (Dec 8, 2010)

Just throwing it out there, seems glass would be brittle, although we've all seen it flex, though not as much as gyp. Stone? Again, seems brittle, but it also will flex, as does concrete. So what's the answer? I agree with brudgers, gyp would NOT be considered brittle in my book.


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## rktect 1 (Dec 8, 2010)

Thanks B,

This means they can use the l/120 and not l/240 which helps lots.

On the plus side with the l/120, I did find a 6" stud that can be used with 5/8" drywall both sides for a height over 35 feet.

I can't wait to see what they built on site.


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## Paul Sweet (Dec 8, 2010)

I think that brittle usually refers to plaster or tile.


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