Yes, or something much better. Redguard is the lowest of the low, and hardly ever done correctly. Look at at USG’s system.

Hydroban is a similar.

Cement Board (including Hardi) is not waterproof at all.

Are your walls tile or are you using a shower kit?

Tile.

The manufacturer told me waterproofing on top/front is not required. Vapor barrier behind cement board depends on local codes. Reason for no waterproofing requirement is hardiebacker is moisture resistant and tile/grout will be sealed.

Regarding the upstairs bath, the tile contractor told me to paint (or prime?) the seams/screws if I wanted more assurance against water seepage. That bathroom remodel is 7 years old and seems fine.

So I guess there are a lot of diverse opinions.

Remember I am not doing the floor, only the walls. I may do a niche but I would try to use a single piece of tile for the base of that. I am slightly concerned about the bottom corners. (I dry the niche every shower but I’m not sure everyone would.)

So I guess there are a lot of diverse opinions.

Oh my

The studs are what need protection. If you have a vapor barrier behind the CBU and in front of studs you would not want to use red guard or a membrane for that could cause a " mold sandwich". Either use a poly vapor barrier behind the CBU or use a membrane on top of CBU not both. But you need to do one or the CBU acts like a sponge that will wick water to your wood studs.

As to how you covered the screws that seems like a risky short cut. Read the cement board specs as to the proper way to cover screws and tape this time.

No. There are only diverse opinions from hacks and non professionals.

Buy a TCNA manual and read it yourself. Waterproofing is required. And you have been talking to complete idjuts. And likely will have a tearout in a year or two.

https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook/957-2018-tcna-handbook-for-ceramic-glass-and-stone-tile-installation.html

But, you’d do better in the meantime to just hire better on the front end. Especially since you don’t know what you are doing enough to attempt to DIY.

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

As to how you covered the screws that seems like a risky short cut. Read the cement board specs as to the proper way to cover screws and tape this time.

They may have done the thinset prep before I did the paint. It was a while ago.

Thanks to those of you who provided helpful and non-judgmental comments. I appreciate the technical explanations.

Look. The Long and the Short Of it is that you EITHER put plastic on the studs and cover it with ceement board and tile it....or you DON'T and use Hydroban or Redguard or Kerdi.... ANY type of surface applied membrane on the face....but NOT both. If you do. you have a "mold sandwich" which is NOT good. Choose wisely, grasshoppah.....

I’ve been reading a bit about pros and cons of vapor barriers and it sounds like they are a local issue, at least for exterior walls. I live in a dry climate with moderate temperatures which leads me to believe the vapor issue is more forgiving than some other areas. Things dry out quickly here - wouldn’t want to trap moisture. I will talk to multiple locals about recommendations regarding vapor barriers in walls here. I may also do a test with a piece of the backer board. And of course I will do more research - the mechanics of this is interesting! I don’t think I will find absolute consistency in recommendations, unless it is local.

I am leaning toward plastic on the studs because that is consistent with what the manufacturer said, but I want to make sure that local installation experts agree that it won’t restrict any drying that may be needed.

If you want to know the right way to fix your Honda Civic, you buy the mechanic’s manual. And that assumes that you have the Waterloo box full of MAC and the occasional Snap Ons, and an empty spot in the garage, or at least a shade tree in the country where the neighbors won’t get pi$$y about parts being spread all over the yard.

You don’t dive in and start pulling things apart without relabeling them, and then put things back together except for a few leftovers. That would be an extremely foolish approach, wouldn’t it? Because it would only make things worse.

You’ve already got one future water damaged project percolating mold inside it that you’re just waiting to become obvious. You want more water damage?

If you are going to take the additional time and inconvenience to attempt to DIY something, do it correctly. Otherwise you are no better than the $1.98 hacks you’ve been talking to that never heard of the TCNA. Those rare your Craigslist shade tree guys who own a wrench or two, and who might be able to halfass a brake job, but if you let them touch your transmission, you’re the idjut selling yourself their con and ignoring the warning signs.

Buy the darn industry bible. Argue with if, if you even understand it. If you don’t, then you aren’t qualified. And neither is anyone else who wants to go against industry standards.