CBU-Sloped mortar bed question

[FIRE MIKE]

Hello,
I live in SW Florida, and I'm a homeowner who enjoys working on my own home. I'm currently remodeling our master bath, and I have a question regarding our shower. The house is a single story on concrete slab, built in 1992. The existing shower was a disaster, as most of you can imagine. No waterproofing, tile on green board, etc... It basically fell apart. The bugs and mold have been mitigated, and the existing deck mud pan has been completely removed back to the depressed concrete slab.

My plan was to rebuild with a new deck mud sloped mortar bed, cement board walls and use a topical waterproofing membrane (Ardex 8+9, or Hydroban) and a bonding drain flange (FloFX). I know that many recommend NOT burying the CBU into the deck mud, and I understand the rational behind this when using a traditional preslope/PVC liner arrangement. Is it still recommended to keep the CBU above the pan, even with a topical waterproofing membrane? I've seen few do this, so I'm asking. I'm planning to follow TCNA B422-19, but I noticed it depicts the CBU buried behind the sloped mortar bed. Just trying to do things right..

Thanks in advance,
Mike

[Tool Guy - Kg]

Welcome to the forum, Mike!

It’s perfectly fine to bury a “true cement board” like Durock into the deck mud when building a traditionally built shower. So it’s perfectly fine in your situation.

[cx]

Welcome, Mike.

In the B422 method it would matter not at all whether you used a true cement board (ASTM C1325) or a fiber/cement board (ASTM C1288), or even a gypsum wallboard if the waterproofing membrane manufacturer allows that.

Goldstein is correct, of course, about the traditional shower receptor construct, but that's not what you're making.

My opinion; worth price charged.

[Tool Guy - Kg]

Just tying to make a point to make Mike confident.

[FIRE MIKE]

Thank you. My only concern was I have read and seen where several people say never to do it on a traditional mortar bed with PVC liner situation, due to the potential for the CBU to wick up water. With my install, using a topical waterproofing membrane, I can see how that potential problem does not exist. However, I wanted to double check in case I was missing anything. Anyone have any tips/tricks on using Ardex 8+9?
Thank you,
Mike

[FIRE MIKE]

Hello,
I'm planning to use Noble products to rebuild my master bath shower. My house is SOG, and I plan to put in a deck mud slope with a linear drain and use CBU for the walls. I would like to use Noble Freestyle Linear Drain, as I feel they are a superior design, with the "clamping ring". What are everyones thoughts on the Noble TS versus their Aquaseal membranes? I know the Aquaseal is thinner. Also, what are everyones thoughts on their Noble EXT adhesive, versus thin set?
Thanks in advance,
Mike Monroe

[cx]

Mike, it'll help if you'll keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered. A moderator can give it a more generic title any time you'd like to suggest one.

I've never installed one of Noble's linear drains, but I've got to think I'd want the thinner membrane for use with it.

I don't see any advantage to use of their EXT, rather than thinset mortar, for a shower floor installation. Significant advantage when using their membranes on a floor for crack isolation, though.

I'll see if we can get our resident Noble rep to comment.

My opinion; worth price charged.

[jadnashua]

The only advantage I know of using their adhesive versus thinset is how soon after installation you can flood test...with the adhesive, I think it's 15-minutes versus (usually) overnight at least. The buildup on seams MIGHT be slightly less.

[e3]

Both the TS and Aquaseal are suitable in shower applications. TS being 30 mils and made from CPE vs 16 mils for Aquaseal is much more robust with a low per rating. That comes more into play in a steam room then a shower..
Aquaseal was developed as a price point option to other products from other companies.
Aquaseal, like the most others, is manufactured from a much less expensive plastic--(PE)
TS has been on the market since 1982 and has a life time warranty.
EXT faster, easier and provides a stronger bond the thin set. Both membrane provide crack isolation and Uncoupling..

[cx]

And is the thinner membrane better to use with that linear clamping drain as I'm suggesting, Eric, or does it really make any difference?

[e3]

doesn't really matter, Both work with the linear drain.

[FIRE MIKE]

I really like the Noble Freestyle Linear Drain with the clamping assembly, however I think the cost is going to be prohibitive....($700 for a drain?). There are a few others that have a clamping mechanism, such as the QuickDrain, and the Infinity Universal. I would like to hear about any positive or negative experiences with some of these other linear drains, using a membrane such as Noble TS. Also any insight on PVC housings versus SS? Would a flanged linear drain and simply attaching the membrane to the SS flange with Noble Sealant, as many drain manufacturers suggest, be the better option than trying to go with a clamping drain? Am I over thinking this? Thanks.

[FIRE MIKE]

Hello,
Does anyone have any experience with Noble’s Pro Base II, specifically the single slope? I can’t wrap my head around how these foam bases handle a persons weight and don’t compress and contribute to cracking. Noble apparently has a honeycomb composite layer on top of theirs which adds to its strength. Can anyone share any experiences? Am I being over cautious and concerning myself with something that I shouldn’t worry about?

[jadnashua]

FWIW, foam is used in road and bridge construction all of the time today https://universalconstructionfoam.co...ridge%20weight.
The foam used in a shower pan is denser than what you might see in a coffee cup, but is often made of the same stuff...just denser.

Once you put a waterproofing membrane bonded to it then a rigid tile, unless you use really small tiles where a point load might be a problem, the psi loads on it are usually quite small. Most people don't dance in their shower with high heels on, but that might not be a good idea!

Note, of the foam pans I'm aware of, the only one that has a tile size limit is Wedi, and for tile 2" or smaller, they require epoxy thinset (and maybe grout?, not sure on the grout) which is stronger than a cement based one. Rounded bottom pebbles might be a problem with a foam pan as getting them fully bedded is harder, but those with a flat, cut bottom should work. Note, pebbles often recommend a steeper slope so things flow well and don't pool around the crown of a pebble, but other than that, not an issue. A mud pan is easier to adjust for that situation.

You must attain good workmanship to fully support your tiles so the load is spread out evenly.

The general comment on foam pans is that they aren't as accommodating to the typical floor...the drain must be nearly perfectly centered where the pan expects it, and the floor beneath must be perfectly flat and level...two characteristics that don't exist without some prep in most circumstances. If they do exist, or you're willing to make it so, they can work great.