sheetrock joists on wood framed building

[Hyrax4978]

Where in the code does it dictate that you need to sheetrock the bottom of wood joists on wood framed projects. small commercial building. Will have ACT hung below the wood joists/sheetrock for lights, ducts etc.

Isn't there a code that requires sheetrock on the bottom of the joists? i just can't seem to find it.

Thanks,

 

[classicT]

Good morning -

Would be helpful to know which edition code you are under. Many different reasons that GWB may be required. What construction type is the project?

 

[RLGA]

There is no direct requirement to apply gypsum board to the underside of joists. If the assembly is required to have a fire-resistance rating, then a tested fire-resistance-rated assembly would be required, thus, the application of gypsum board would most likely be the material to achieve that rating.

Another thing may be the type of insulation installed between the joists. If a spray foam insulation was used, then a thermal barrier is required. 1/2-inch gypsum board is the prescriptive method for complying with the requirement, but the code permits other approved materials.

 

[Hyrax4978]

Its 2015 IBC. the insulation would be batts. Its not a rated separation.
One thing i was thinking was it has to to with things like fire blocking. to close off the chase created by the joist cavity that would allow the fire to spread. No different than not leaving a wall cavity open to the space above the acoustical ceilings. I can dig into the fire blocking code easily enough.
But if there was some other code in some other area i can't find, It would just be nice to hone in on the code section, so i can verify that i have all bases covered. Thanks,

 

[Mr. Inspector]

If the batts have paper on them you need drywall over them. Energy code requires air sealing.

 

[Mr. Inspector]

It's in the IECC section 402.5 Air Leakage

 

[steveray]

No requirement....I think Ron nailed it....If there is no "sheathing" on the framing, there is no concealed space....If it is full of insulation it is fireblocked....

 

[SCBO1]

Ron's on it.

Be aware of batt insulation coming in contact with light fixtures that are not rated IC for "Insulation Contact". I've seen this scenario where they install a CT grid system and then lay the insulation over the grid and light fixtures.

 

[Paul Sweet]

The insulation needs to have a foil vapor barrier with flame spread of 25 or less (IBC 720). It should be stapled to the bottom of the joists, and seams will probably have to be taped for air leakage.