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Old 06-25-2017, 03:54 PM
 
5 posts, read 3,099 times
Reputation: 20

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I am remodeling a bathroom in a condo, and the shower shares a wall (actually two) with a neighbor(s). The existing walls consisted of regular 5/8" gypsum board on the walls. I could not find any information for substituting gypsum board with cement type boards.

The code seems to be to use 5/8" gypsum board for the load bearing walls, and partition walls between units. I was wondering if using 1/2" HardieBacker would meet the code requirements for these types of walls. From the little information that I have come across, the 5/8" gypsum board between units is for noise control, and on the load bearing wall has the added function of increasing shear strength.

I looked up some numbers for the boards and did not find terminology that I would expect to see for this comparison such as, possibly, shear strength. The numbers that I found for HardieBacker were confusing because the Flexural Strength for the 1/4" board (2,100 psi) seems higher than for the 1/2" board (1,700 psi) indicating that the 1/4" board is stiffer than the 1/2" board. I must not understand what this number means even after looking it up. The numbers for the 5/8" gypsum board (~150 lbf) seemed to make more sense and follow the explanation of Flexural strength which were indicated using Pound Feet and Newtons. The Compressive Strength numbers just seemed to indicate that the 1/4" board (7,000 psi) was slightly more resistant to crushing than the 1/2" board (6,500 psi), both of which greatly outperform gypsum (~400 psi).

In the worst case, I was thinking that I may need to put up the 5/8" green board and then the 1/2" HardieBacker on top of that, but that seemed a bit excessive.

I apologize for being long winded, but I was not certain what information would be most relevant and I did not want to look like I made no attempt to research this at all.
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Old 06-25-2017, 06:28 PM
 
Location: SoCal
6,419 posts, read 11,571,173 times
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I can't help you with figuring out whether it's a physically suitable replacement. But even if it is, presumably the work you're doing will need to pass inspection. And if that substitution doesn't meet code, it won't pass inspection even if it's physically suitable. So in addition to checking for structural integrity, check that it'll pass inspection.
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Old 06-25-2017, 07:25 PM
 
18,172 posts, read 16,324,110 times
Reputation: 9325
Quote:
Originally Posted by dapperdan999 View Post
I am remodeling a bathroom in a condo, and the shower shares a wall (actually two) with a neighbor(s). The existing walls consisted of regular 5/8" gypsum board on the walls. I could not find any information for substituting gypsum board with cement type boards.

The code seems to be to use 5/8" gypsum board for the load bearing walls, and partition walls between units. I was wondering if using 1/2" HardieBacker would meet the code requirements for these types of walls. From the little information that I have come across, the 5/8" gypsum board between units is for noise control, and on the load bearing wall has the added function of increasing shear strength.

I looked up some numbers for the boards and did not find terminology that I would expect to see for this comparison such as, possibly, shear strength. The numbers that I found for HardieBacker were confusing because the Flexural Strength for the 1/4" board (2,100 psi) seems higher than for the 1/2" board (1,700 psi) indicating that the 1/4" board is stiffer than the 1/2" board. I must not understand what this number means even after looking it up. The numbers for the 5/8" gypsum board (~150 lbf) seemed to make more sense and follow the explanation of Flexural strength which were indicated using Pound Feet and Newtons. The Compressive Strength numbers just seemed to indicate that the 1/4" board (7,000 psi) was slightly more resistant to crushing than the 1/2" board (6,500 psi), both of which greatly outperform gypsum (~400 psi).

In the worst case, I was thinking that I may need to put up the 5/8" green board and then the 1/2" HardieBacker on top of that, but that seemed a bit excessive.

I apologize for being long winded, but I was not certain what information would be most relevant and I did not want to look like I made no attempt to research this at all.
It is not just noise or strength it is the fire rating. Check that.
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Old 06-25-2017, 07:56 PM
 
5 posts, read 3,099 times
Reputation: 20
Quote:
Originally Posted by expatCA View Post
It is not just noise or strength it is the fire rating. Check that.
I can understand/accept that, but HardieBacker will beat gypsum board by a long shot. It can be used around fireplaces and fire pits.

Thanks for pointing that out.
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Old 06-26-2017, 08:07 AM
 
Location: San Diego
50,153 posts, read 46,811,218 times
Reputation: 33984
Are you looking for code control, noise or moisture fixes?
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Old 06-26-2017, 08:28 PM
 
5 posts, read 3,099 times
Reputation: 20
Quote:
Originally Posted by 1AngryTaxPayer View Post
Are you looking for code control, noise or moisture fixes?
To know that I am meeting code and take it from there.

Last edited by dapperdan999; 06-26-2017 at 08:41 PM..
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Old 06-26-2017, 09:31 PM
 
5 posts, read 3,099 times
Reputation: 20
The building code is on the website that I was on. I clicked on the PDF link thinking that it was the same as the HTML link, but the PDF is just the amendments to the HTML linked document.

Learned that HardiBacker boards are not 1-hour fire rated because they are too conductive. (makes sense)

End result is using 5/8" Fire code core gypsum board and maybe 1/4" HardieBacker on top since it will have the gypsum board to back it up.

That wall may be as thick as 1-1/4" with the tile installed.
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Old 06-26-2017, 09:35 PM
 
Location: La Costa, California
919 posts, read 786,639 times
Reputation: 2023
I think that is a very wise choice
Dave
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Old 06-26-2017, 09:45 PM
 
Location: Dangling from a mooses antlers
7,308 posts, read 14,647,506 times
Reputation: 6237
You really want to get Durock cement backer board. It surpasses gypsum as it is non-combustible.

https://www.lowes.com/pd/DUROCK-Bran...-Board/3044009
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Old 06-27-2017, 02:44 AM
 
5 posts, read 3,099 times
Reputation: 20
Quote:
Originally Posted by stiffnecked View Post
You really want to get Durock cement backer board. It surpasses gypsum as it is non-combustible.

https://www.lowes.com/pd/DUROCK-Bran...-Board/3044009
Funny you should mention this because after doing some more surfing and research I came to the same conclusion. Stronger than gypsum board and just as good of a fire-resistance rating.

Thanks for you input.
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