Hello....I am attempting my first shower tile project and I have a few questions that I am hoping someone clear up for me. It's a small shower, 36x38, and I really want to attempt this myself.

Here are my (1st set of …) questions:

Can cement board be used for the curb rather than mortar? If so, how is it to be placed? Any specific installation requirements?

Is Hardie Board an acceptable cement board?

Do I need a vapor barrier behind the cement board?

For the cement board joints, do I need to tape and mud them as well? If so, what is the best thing to use?

Would Kerdi waterproofing (or similar) provide me with additional protection? Is it necessary?

For the pre-slope, I have seen some posts in regards to using cement board to create the “step” towards the drain; I assume that is NOT recommended?

Any help would be greatly appreciated. Thanks, Jay

If you are using the traditional preslope and liner method, then you can't use CBU on the curb. If you go with a liquid or membrane waterproofing, then CBU is acceptable on the curb.




Hardi is good in certain applications, and is certainly approved for use in showers. It's not my personal preference for showers, though. If I used CBU in a shower, I'd use Permabase or some equivalent. My primary gripe with Hardi on walls is that it's slightly thinner than 1/2", so it doesn't transition well to drywall.



If you're going to use a surface-applied waterproofing, such as Kerdi membrane or Redgard, etc., then no, you won't need a vapor barrier behind the CBU. If not, then use 6 mil plastic on the studs.




You need to tape and mud the joints on any CBU with 2" wide alkali-resistant mesh tape and thinset. The only exception to this that I'm aware of is if you're using Kerdi.




While not necessary, Kerdi would definitely provide you with a better waterproofing system. It's a little more expensive, but looking at the big picture, it's not that big of an expense. A Kerdi shower will dry out faster, which reduces the chances of mold growth, which in turn makes your shower last longer. There are a number of liquid waterproofing products on the market that work quite well. I've found them to be a bit more time-consuming since you have to allow for drying after each application, but that may not be a concern for you. The advantage with liquids over membranes is that there are no overlaps, so they make tiling easier for a DIY'er.



No, you'll just want to use deck mud.

Kman,

Thanks for the info! I appreicate you taking the time to provide me with all that info!
As you suggested, I am going to pursue a liquid waterproofing product as time concerns are not an issue for me and it sounds like that will provide me with better results.
Can you recommend a good liquid product to use?

Thanks, Jay

There are quite a few out there.

The latest from Laticrete is Hydroban. While more expensive, it can be applied without the use of fabric or mesh on the corners and seams. Applying fabric can be messy, so that may be the best option for you.

Laticrete also makes 9235 which works well. Custom Redgard is available at Home Depot. Both of those require fabric or mesh in the corners and seams.

For any of those, I would recommend the use of a cement board. For the floor, you'll need to use either a PVC liner with a preslope and mud curb, or allow the mud floor to dry for three days and apply a liquid waterproofing.

Liquid waterproofing on the floor requires the use of either a Kerdi drain, or a standard clamping drain with a divot in the mud around the drain, as well as fabric around the drain. For a DIY'er, I don't recommend the divot method. The kerdi drain is expensive, but a little easier to use and a little more foolproof.

Evening Kman,

Question I have in regards to the installation of the CBU: I have begun installing the CBU over the liner leaving approx 1/2 inch space to prevent the wicking. How close to the liner should I be screwing in the CBU? Currently I screwed in the CBU about 15 inches up from the liner but I do notice that the CBU is pushed out a bit from the liner material towards the bottom. How close can I screw in the CBU to correct the "warping"? I have seen some pics where it appears to be only 3 inches or so from the liner? Is that recommended?
Thanks, Jay

With a liner, the studs need to be notched back 1/8", and maybe a little more in the corners, to allow for the thickness of the liner. You would also have some solid blocking between the studs to keep the liner up. The studs are normally notched to about 3" above the level of the step. You don't want to put screws/nails lower than this point. The CBU will naturally stick out slightly at this point, but when you pack the final slope over the liner, the deck mud will push the CBU against the liner/studs and hold it in place.

Take a look at these pictures before you go any further:

http://www.ontariotile.com/preslope.html

I actually had these instructions printed out and that is what I used to complete the liner and pre-slope. They were VERY helpful! The only thing I did not do was the notching of the studs as I did no think of that...rookie mistake I guess. Since I only have 3 bottom boards of CBU attached I am removing them and notching the studs. Thanks, Jay