# Water-resistant Gypsum Backer



## bona fide (Feb 16, 2010)

> 2007 CBC section 2509.2....shall be used as a base for wall tile in tub and shower areas and wall and ceiling *panels* in shower areas


Does this mean greenboard cannot be used as backer for manf. *panels* like cultured marble or fiberglass surrounds at showers in residential applications?

Thanks


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## Span (Feb 16, 2010)

Re: Water-resistant Gypsum Backer

Not sure for panels like cultured marble but if is for fiberglass panel backer board will be OK.


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## bona fide (Feb 17, 2010)

Re: Water-resistant Gypsum Backer

Span

what code section can i use to verify this?

Mf. cut sheet for name brand SHEETROCK, Gypsum Panels, Water- Resistant



> Limitations: Do not use in tub or shower surronds, or other areas subject ot constant or excessive moisture.


Thanks


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## Span (Feb 17, 2010)

Re: Water-resistant Gypsum Backer

Try Gypsum association ( GA-239-04 ) regarding water-resistant gypsum backer board for ceramic

tile in wet area. It will be helpful in understand that green board is water resistant not water proof.

http://www.gypsum.org/download.html

Some times code enforcement officer want me to show where is the code? where is the words it stipulated?  Such as garage floor surface need to be non combustable, But where did the code

says NO tiles or Marbles? only approve materials.


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## bona fide (Feb 17, 2010)

Re: Water-resistant Gypsum Backer

I may be trying to read to much into the code, but my concern is that the word panel used in the quote below is refering to fiberglass or cultured marble panels applied in showers.



> 2509.2 Base for tile. Cement, fiber-cement or glass mat gypsum backers in compliance with ASTM C 1178, C 1288 or C 1325 and installed in accordance with manufacturer recomendations shall be used as a base for wall tile in tub and shower areas and wall and ceiling panels in shower areas.


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## Span (Feb 17, 2010)

Re: Water-resistant Gypsum Backer

The " Panel " for me, it means green board was being put above tub or shower enclosure.

On 2509.3 Limitatations. shall not be use in following locations.

               1. Over vapor retarder in shower or bathtub compartment.

                2. Where there will be birect exposure to water or in area subject to continuous

                    high humidity.

                 3. on ceiling where frame spacing exceed 12" for 1/2" greenboard and more than

                     16" for 5/8".

Because a lot of house use greenboard for shower compartment. I always ask contractor to change it. But still allow them to use above 70" from bottom of tub.


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## peach (Feb 17, 2010)

Re: Water-resistant Gypsum Backer

how many times do you see water droplets hanging from the ceiling above the shower?

I think you need Duro-rock on the ceiling of a shower, anyway.


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## TJacobs (Feb 18, 2010)

Re: Water-resistant Gypsum Backer

It is a shame that if a manufacturer says not to use their product in a particular application, we still need a code to prohibit it...I think the code text is pretty cut and dried myself.


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## Architect1281 (Feb 20, 2010)

Such a Prohibition exists

R702.3.8.1 Limitations.

Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity.


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## rktect 1 (Feb 22, 2010)

Re: Such a Prohibition exists



			
				Architect1281 said:
			
		

> R702.3.8.1 Limitations.Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity.


A shower ceiling does not get direct exposure to water nor continuous high humidity.  But I always check the span of ceiling joists and they always seem to use trusses at 24" o.c. and 1/2" greenboard.  So I tell them it can't be done.  Then they change to durock.


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## bona fide (Feb 23, 2010)

Re: Water-resistant Gypsum Backer

i agree with peach.

water does accumulate at the ceiling. Heat rises. Hot vapors rise to the ceiling of a tub or shower enclosure, exposing the ceiling to continuous

moisture while the tub or shower is in use.

Continuous does not mean 24/7. Continuous only while the tub or shower is in use.  My opinion only.

 what does the code require???

Thanks


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