# 1/2" Gypsum Board Ceiling in Commercial Building



## benny (Feb 21, 2012)

I'm heading to a sheet rock inspection at a new eye clinic. The plans show 5/8" gypsum on the walls and ceiling. The contractor has installed standard 1/2" gypsum throughout. The roof system is engineered trusses at 24" O.C. The IBC references GA-216 and ASTM C 840 which I don't have. However, 1/2" gyp is listed in Table 2508.5. What is confusing me is that the IRC only allows standard 1/2" gypsum with joists at 16" O.C. max if water based texture material is used; 5/8" gyp or 1/2" sag resistant required with trusses at 24" O.C. with water based texture (Table R702.3.5, footnote d). I plan to kick it back to the architect on my inspection report.


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## codeworks (Feb 21, 2012)

not in accordance with approved plans, failed, don't try to rationalize irc and ibc differences, eye clinic is ibc straight up. irc (imo) yuks, if you get my drift. through it back to the contractor for not following plans, if architect made change, it should go through approval process


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## benny (Feb 21, 2012)

So if the architect gets me something in writing regarding the change I'm good to go?


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## fatboy (Feb 21, 2012)

In writing, signed and stamped. Just like the plans are.


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## north star (Feb 21, 2012)

*= =*

Just make sure that you check the appropriate code sections

[ in the applicable edition of the IBC ] for compliance of any

REVISIONS / submittals......Sometimes the RDP isn't compliant

with their designs [ i.e - perform your due diligence  ].

*= =*


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## RLGA (Feb 21, 2012)

Per ASTM C 840, Footnote A of Table 2: "Gypsum board ceilings to receive hand or spray-applied water-based texture material shall be applied perpendicular to framing and shall be either (i) 1/2 in. (12.7 mm) Gypsum Ceiling Board (see Specification C 1396/C 1396M) applied to framing not more than 24 in. (610 mm) on center, or (ii) other gypsum boards not less than 1/2 in. (12.7 mm) thick for 16 in. (406 mm) on center framing and not less than 5/8 in. (15.9 mm) thick for 24 in. (610 mm) on center framing."

Basically says the same thing as the IRC. What is installed is noncompliant with the IBC.


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## benny (Feb 21, 2012)

This is the architect's response:

"its not a problem on my end Clint... we didn't take any shear values or anything for the gyp bd...  so 1/2" is fine...  if it was water-resistant gyp bd for a particular reason, then code requires 5/8" gyp bd on anything over a 16" span...."


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## RLGA (Feb 21, 2012)

I should probably qualify my post:  If all the contractor will do to the gypsum board ceiling is paint it, then 1/2 in. gypsum board is okay.  If wet texturing material is to be applied, then the installation is not compliant with the IBC, and must have either 5/8 in. board or 1/2 in. sag-resistant ceiling board installed.

The problem is that the wet texturing material will soften regular gypsum board and cause it to sag between the ceiling joists.


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## fatboy (Feb 21, 2012)

""its not a problem on my end Clint... we didn't take any shear values or  anything for the gyp bd...  so 1/2" is fine...  if it was  water-resistant gyp bd for a particular reason, then code requires 5/8"  gyp bd on anything over a 16" span....""

Your response should be.........can you please cut me an original wet stamped letter saying the same, since the installation, although compliant in your opinion, contradicts the reviewed plans.


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## benny (Feb 22, 2012)

http://www.usg.com/rc/data-submittal-sheets/panels/sheetrock/sheetrock-ultralight-panels-submittal-en-wb2501.pdf

All is good. It turns out the sheet rock is a newer product called "light rock" that meets ASTM C 1396. I guess this is what happens when design changes are made without notifying the architect and building department.

Thanks for your input everyone.


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## RLGA (Feb 22, 2012)

The manufacturer of LightRoc gypsum panels states that it complies with Section 5 of ASTM C 1396, which is for regular gypsum board...sag-resistant ceiling gypsum board is specified in Section 12.  If the intent is to apply wet texturing material, it would still be noncompliant since ASTM C 840 requires the ceiling-type panels for such applications.

Either way, as fatboy eludes to, it was a change from the approved set of plans.

As for the architect, if the thinner panels were installed without his approval, (i.e. no written or verbal authorization--it should be a written contract modification), the architect must reject it as nonconforming work, since it does not comply with the contract documents, and inform the owner--only the owner can accept nonconforming work.  Otherwise, the architect has accepted some liability in which he/she didn't intend to accept.


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## benny (Feb 22, 2012)

"Can be used on ceilings with 24" o.c. frame spacing when water-based texture is applied" (perpendicular installation)

"Meets or exceeds ASTM C-1396 specifications for 1/2" gypsum wallboard and 1/2" gypsum ceiling board.

Complies with the requirements of the International Building Code and International Residential Code as both

regular wallboard and ceiling board."


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## RLGA (Feb 22, 2012)

benny, where is that stated?  The product data on American Gypsum's website does not state that.


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## RLGA (Feb 22, 2012)

I take that back, it states it in the intro, however, the supporting information (i.e. ASTM Standards reference) indicates it is not the sag-resistant ceiling type.  I think somebody in marketing screwed up somewhere.


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## fatboy (Feb 22, 2012)

"As for the architect, if the thinner panels were installed without his approval, (i.e. no written or verbal authorization--it should be a written contract modification), the architect must reject it as nonconforming work, since it does not comply with the contract documents, and inform the owner--only the owner can accept nonconforming work. Otherwise, the architect has accepted some liability in which he/she didn't intend to accept."

I agree completely, may work, may be compliant, but it's not what been designed.


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## RLGA (Feb 22, 2012)

I've notifed American Gypsum of the discrepancy in their literature.  We'll see if it gets anywhere.


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## gbhammer (Feb 22, 2012)

RLGA said:
			
		

> I've notifed American Gypsum of the discrepancy in their literature.  We'll see if it gets anywhere.


Your professionalism is astounding. I must say I have the utmost respect for RLGA.


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