Master bath reno questions [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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05-27-2019, 03:03 PM
New to the forum- Searched through a bunch of threads all really know your stuff! We just gutted the master bath to the studs, remediated some mold that was behind the jacuzzi tub that we removed. We are working with a contractor to re-do the bathroom...I want to do it right. We've purchased a shower basin with a bench, will use tile on the 3 shower walls. Contractor has purchased the hardibacker, I am just trying to get the best info from a moisture barrier/waterproofing perspective.
1. Moisture barrier between hardibacker/studs or not? 2 of the 3 walls are external.
2. If yes, do you terminate the barrier at the top of the basin or do you have it run under the pan to the drain?
3. What is the right way to install the hardibacker as it relates to seams? How about where he screws through it?
4. I've read about redguard- I guess depending on the answer to #1, would you do both?
5. What tips would you recommend as far as the redguard install goes?

One thing to note about the mold that was found- all of it was at the same level- tub level. There was tile there before, no moisture barrier. Nothing was at shower level. Not sure what conclusion to draw about what failed. They had the jacuzzi tub installed next to OSB, then blown insulation that was packed in between the studs, then the outer layer OSB.

Hope I'm not forgetting anything, but am panicking a bit as I want to do this right and only once. Please ask me questions if I have not given the complete picture. Thank you

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05-27-2019, 04:18 PM
Welcome, Jon. :)

We've purchased a shower basin with a bench, Not sure just what you mean there. Perhaps a photo of what you've got or a link to it online. You can't yet post links, but just paste in in your reply with an extra space in the www and a moderator will light it up for you. Photos you can attach from storage on your computer using the paper-clip icon above the Reply dialog box.

1. Might be an option, but first we need to know about your receptor, or whatever it is you're calling a "shower basin."

2. See #1.

3. Per the product manufacturer's instructions, available online if he didn't get a copy with the product.

4. Definitely would not do both. Pick one method or the other.

5. I would recommend using something other than Hardiebacker if you plan to use a liquid-applied waterproofing membrane such as RedGard. You can make a primer per the RedGard manufacturer's recommendations for use over very thirsty materials such as Hardiebacker, but I'd start with a different backer board were it mine and I was planning to use a CBU. There is also the problem of the Hardiebacker being only about 7/16ths" thick and matching up to half-inch drywall outside the shower if that's a consideration.

My opinion; worth price charged.

05-27-2019, 04:29 PM
Basin is like this one, but not this one exactly.

What CBU is recommended for use with RedGard?

05-27-2019, 04:43 PM
Ouch. Doesn't look like a fella could use a glass enclosure on that and I can sure see water containment problems with that thing and a shower curtain. If it at least had a tiling flange all the way around, including down the front, I can see being able to waterproof it, but..........

I would at the very least want to extend the CBU well past the front of that fixture and waterproof the walls with a sheet-type direct bonded waterproofing membrane that could be turned onto the surface of the receptor a little and bonded with a suitable sealant.

Gonna have the same problem one has waterproofing a tub/shower in the front, but exacerbated by the open front area. Can't offer any evidence for my concern as I've never dealt with anything quite like what you've got there. And never hope to, now that I see it.

Maybe someone else has installed one of more of them and can offer better insight.

Choice of CBU is entirely up to you, I'm just pointing out a couple of the known problems we see here on a regular basis with the Hardiebacker.

My opinion; worth price charged.

05-27-2019, 05:06 PM
Guess I'm not understanding why this basin is any different than the other ones you can get?

Based on what you see, can you answer my #1 and #2 regarding moisture barriers?

"I would at the very least want to extend the CBU well past the front of that fixture and waterproof the walls with a sheet-type direct bonded waterproofing membrane that could be turned onto the surface of the receptor a little and bonded with a suitable sealant."

The recommendation above regarding a direct bonded waterproofing membrane- is that for the 3 exposed walls or one area specifically? And, what is a sheet type direct bonded waterproofing membrane?


05-27-2019, 05:40 PM
I'd like to know what so-and-so decided it was a good idea to stop the tile flange at a 45 degree angle about three inches back from the corner of tubs nowadays.

The hurt I'd put on him.....:stick::deadhorse:bonk::bang::tazebro::whip:

05-27-2019, 06:42 PM
Kevin, I know a few years back one group from one of the technical committees was trying to get the plumbing code people and the tub manufacturers to agree to require that flange be at least 1" tall and extend all the way to the front of the tubs. Don't think they ever had any success at all.

05-28-2019, 08:19 AM
I'm wondering why use a shower basin? For that 💰 why not make it all tile. Or all fiberglass if budget is tight. You can't really use drywall and kerdi because you can't protect the bottom edge of the drywall from getting wet.
I think what CX is talking about is the wall board or whatever is used will only have a butt joint along the front edge of the shower basin. So any water there not stopped by the shower curtain will eventually find a crack in the caulking. Unless the base is made sturdy for a shower door track.