CBU preference in a shower

I'll be screwing CBU to studs in my new shower and wondered what backerboard people prefer in this instance. What do you like to use?
I've read Hardibacker is the hardest but not sure if this is the most important criteria.

Another question; It's been noted on this board many times that CBU's offer little or no structural addition. If this is the case then if you put CBU's on studs for a shower where is your structural support coming from?

Ken:

I have read on this site that both Hardi and Durock are used by many folks in a shower application; seems that both work well. When you say, "hardest", what do you mean?

With regard to the structural comment. There is "no" structural load on the wall (specifically, not on the CBU). Think sheet rock on a wall (there is really no strength that sheet rock provides to a wall).

You gonna be using a barrier under the CBU?

Charlie,
I guess what I mean by hardest is the cbu that would have the least amount of potential flex.
Byrne suggests 1/2" and not 1/4" cbu screwed, not nailed, to studs, and I'll do that, on top of poly or roll roofing barrier.

ALWAYS 1/2" CBU on studs, ALWAYS.

Bud, wasn't it a post of yours someplace, sometime, that said Hardi was the "hardest", whatever that means?
What cbu (s) would you recommend in a shower?
Thanks.

I don't know what the manu's numbers are, but Durock appears to be alot more rigid. However, I do not think flex comes into the equation here, but do make sure you have your expansion gaps. Judges?

All of the mainstream CBU's are about the same except Hardi which has the highest compressive strength and the highest flexural strength of them all. Please don't make me go dig out the specs.
In my experience Hardi is slightly easier to split a stud with but even Hardi will breakout when nailed or screwed close to the edge, they are all painfull in that respect.

So, I guess there's no clear opinion on which cbu is best to use in a shower.

Does it make any sense to sister studs together where two cbu's meet to give them an easy screwing surface (ie, where the two studs meet would be where the gap between the two cbu's is) or is this obsessing?

Sistering is obsessing, but what the heck, if it makes ya feel better. If it's on an exterior wall you will lose 6% in insulation capacity. Gotta save oil and the whales.

I'm willing to bet that in a poll, you'd find preferences if any pretty even across the board (more like whatever cbu their supply house carries).

COMPRESSIVE STRENGTH:
Wonderboard 2500 psi
Durock 2300 psi
PermaBase 2250 psi
Utilicrete 2600 psi
HardiBacker 6500 psi

FLEXURAL STRENGTH:
Wonderboard 900 psi
Durock 750 psi
PermaBase 750 psi
Utilicrete 1500 psi
HardiBacker 1700 psi

And for walls, the compressive strength is mostly useless, since it will fail in tension (the flexural strength number basically) before compression (due to bending, say if someone pushs the wall really hard between studs.

Would have never guessd that big a difference.

I thought I used utilicrete once and really didn't seem that different from my norm of Durarock.

Thanks Bud

Ken, Unless your the size of an elephant and wear high heels in the shower It looks like you could use any of the above

I think most people just use what they like best and find easiest to work with.

For me, it's Hardibacker®, because I like that you don't get the crumblies when you cut it, and nail close to the edge (though what Bud said is true; if you get to close to the edge, any of them will break out).

Also, for what it's worth to you, Hardibacker® is the ONLY board that passed all tests for mold and mildew that was recently conducted by an (apparently) independent lab (I don't know who). If that turns you on, use the Hardibacker®.

Other than that, one's as good as another. Use what you think you'd rather work with. Hint: If you don't have the special snapper shears, the Hardibacker® is a bit harder to score and snap than DUROCK® or Wonderboard®

Chuck said;
"Ken, Unless you're the size of an elephant and wear high heels in the shower It looks like you could use any of the above".
My wife wears the high heels with me in the shower. She's pretty thin. I guess I don't need to worry.
Sounds like any of the boards are structurally fine in a shower.

Kinsman said;
"For me, it's Hardibacker®, because. (you can) nail close to the edge (though what Bud said is true; if you get to close to the edge, any of them will break out).

Oops, I tried to say in the previous post;
Kinsman said;
"For me, it's Hardibacker®, because. (you can) nail close to the edge (though what Bud said is true; if you get to close to the edge, any of them will break out).

I had previously asked if it was too obsessive to sister studs together so that you could therefore screw/nail the cbu further away from the edge of the 2x4 studs. I did the math and assuming you screw/nail 1/2" from the edge of the cbu into the stud, with 1/8" gap between the cbu's, then;
With a single stud you'd be screwing/nailing 3/16" from the edge of the cbu.
With double studs (2 studs sistered) you'd be screwing/nailing 9/16" from the edge of the stud.
That seems like a big difference and using double studs would seemingly minimize breakout.
Any second opinions on double studding to minimize breakout?

Thanks for the info Bud, Kinsman and Ken. I think I'll take my Durock back and use the Hardiboard and get the special snapper tool

I have always been told that Hardi is not reliable in wet areas in the long run and to go with a fiberglass cement backerboard rather than the gypsum cement backerboards in those areas and to use the Hardi under wood floors, etc. There are some of the fiberglass cement boards that score and trim a lot cleaner and easier than others while maintaining the compressive strength of Hardi. For instance National Gypsum's Permabase is a clean snapping board and so is SelectCrete's. I've been using the SelectCrete lately because of the lower cost, but any of them will ultimately work I guess.

I have always been told that Hardi is not reliable in wet areas in the long run

Told by whom?

Have you tried "Green E Board"? Appears to be a great product - I like it.

Bud
What is green e board? Would you supply some more info.
Thanks

 http://www.greeneboard.com/