Roof Members - Not Supporting ceiling deflection question

[swsengineer]

IBC table 1604.3 allows lower deflections for roof members not supporting a ceiling. What about a steel or wood deck that is the structural deck and the ceiling. A ceiling is not hung or supported by the deck as the deck itself is the exposed ceiling. Would this fall under

Roof Member
Supporting nonplaster ceiling
or
Not Supporting Ceiling

thanks,

 

[BAretired]

Not supporting ceiling.

BA

 

[woodman88]

I agree with BA, not supporting ceiling.
But be careful of what is being placed on the deck. Had one owner that wanted to tile his existing deck. I had to explain that the deflection requirements of the tile could not be met without replacing or doubling/tripling the existing joists.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[swsengineer]

thanks, I agree too.
It's not a provision I normally use. In this case I have a 3" laminated wood T&G deck that is the ceiling and structural deck. Most of it is fine at L/180 total load, but their is one small area where it's more like L/160 for a few pieces on a hip condition and I was hoping the L/120 would satisfy that. I could apply footnote d which allows the use of .5DL+LL to be used instead of the full DL which makes it plenty ok. I'm not comfortable using .5DL especially when the NDS suggests (not mandatory) using a creep factor of 1.5 on the dead load if worried about long term deflection. I really don't understand the reasoning of the .5DL allowance but then again I haven't tried too yet.