CBU thickness for walls

[johnm07]

I've spent a couple hours researching my question but could not find a clear answer so excuse me if you've answered this before.

I am preparing to start a new shower/tub project and plan to use the Schluter Ditra system. After much reading it appears that installing CBU under the Ditra is the appropriate solution. The correct brand of CBU to use appears to be more of a personal choice.

My question is, what thickness of CBU should be used on the tub shower walls?
(Wall framing is 16" oc)

Thanks
-John

[JoeBoxer]

I've only experience with hardie backer / board. But from checking with the manufacturer, their 1/4" CBU is all you need. However, they do make 1/2" CBU to ease the transition from CBU to drywall, just in case you will eventually interface with drywall.

That beind said, I used 1/2" CBU for wall cause it wasn't that much more expensive, and they ran out of 1/4" CBU when I was looking. The 1/4" CBU from hardie is more than adaquate for the job if you are doing the entire wall in CBU.

[bbcamp]

Joe may be right, and James Hardie may agree with him, but I don't. Considering that you might slip and bump heavily into the shower walls, it doesn't make much sense to skimp on the substrate.

Also, Schluter thinks the preferred substrate for Kerdi is regular 1/2" drywall.

[MudMaker]

John.. howdy.. Have you tried the videos on Schluter installs?
http://www.schluter.com/8_1_kerdi.aspx

[MudMaker]

nother thing... Hardi recommends 1/2" for walls not 1/4".. like Engineer Bob said, ya don't need any CBU...

[johnm07]

Thanks for the fast replies.

I was originally thinking of using drywall but I've read a in a couple of forums about a change in code, 2006 ish, that stated no drywall in shower and tub locations. I honestly don't know the details of what code requires in a bath surround but I want to make sure I do the job right and preferable at or above code.

Sounds like 1/2" is the way to go with CBU or drywall.

Mudmaker, I've read some of the Schluter manual and previewed their videos but I will need to complete both prior to staring the project. Thanks for the links.

-John

[bbcamp]

John, that code change was aimed at "sheetrock showers." Lots of showers were made with drywall or greenboard and mastic. Most failed. The code committee made a sweeping statement, but forgot that one vendor makes a membrane proven acceptable over sheetrock. Your building authority will likely accept Kerdi over sheetrock if you show them the various approvals that are available on Schluter's website.

[JoeBoxer]

I don't know ... der be a whole how too section on wall installation of 1/4" on der manufacture's site.
http://www.jameshardie.com/homeowner...rterInch.shtml

The 1/4" has 7000psi vs. their 1/2" which has 6500psi compressive strength.

Quote from the Hardie FAQ:

Can Hardie 1/4" board be used in a shower wall application? Is a vapor barrier required?
-----------------------
Yes, HardieBacker 1/4'' cement board may be used in a shower. However, we recommend HardieBacker 500 if you need to make a smooth transition to drywall. The board must be mechanically fastened every 8'' on center to the wood or metal studs spaced a maximum of 16'' on center. A vapor barrier is needed if required by local building codes.
-----------------------

Having worked with both, the 1/4" felt denser, and more highly compressed, but the 1/2" is definately more ridgid.

[MudMaker]

Hey Joe... That be a link to Countertops and Floors... I don't think I would ever put 1/4" onna wall, first of all it won't match up... Hardi tells ya to put 1/2"

[bbcamp]

James will also tell you it's OK to set tile on 1/4" backerboard on 5/8" plywood over joists 24" on-center, but I won't.