Mud float vs cement board and waterproofing

7 years ago

We are trying to decide between two tile contractors with similar pricing (for our new build). Both claim their way of doing things is best. One mud floats the entire shower after pan and cement board are installed. The other installs their own shower pan and cement board (says other contractors tend to screw it up) and then uses a Schluter waterproofing method. We have an issue the grout cracking between the wall and floor in our current shower and I want to avoid that. This is our forever home and I don't want any issues with water behind the wall, mold/mildew, etc.

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MongoCT

7 years ago

I m a little confused by the description of what each guy is doing.

Whatever they do, make sure the floor membrane itself is sloped to the drain. Iy's a code violation to install the membrane flat on teh subfloor with sloped mud on yop of it.

"One mud floats the entire shower after pan and cement board are installed."

Is this guy floating mud directly on the cement board? Floated walls are typically (at least in my experience) tar paper and then expanded diamond mesh on the walls, with the mesh wrapped through the corners. Then the walls get floated with mud. A tile backing surface like that with mesh wrapped through the corners will not crack on the wall-to-wall corners, so the corners can be grouted.

If you're looking to avoid corner cracks, you'll have better success with a fully floated shower that has mesh wrapped through all corners, versus tiling over a lightweight tile backer board like cement board.

I do like Shluter's Kerdi membrane, as well as other surface-applied membranes. They can be installed over cement board, and even over a floated mud wall.

I think every tiler should want to control the process from studs-to-tile. The tile can only be as good as what it goes over.

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Comments (9)

PRO
Creative Tile Eastern CT
7 years ago
In addition to Mongo's advise. Voice your concern about the grout cracking where the wall meets the floor. The response should be caulk / sealant (100% silicone) is installed at a change in plane. This is a basic detail. If the installer intends on using grout select another installer.
housebuilding126 thanked Creative Tile Eastern CT
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If he does mud walls, is something else needed though (on top), besides the paper behind it? No, just as with a thinset installation, all that's needed is the vapor barrier, which is what the tar paper is. This where the advantage of the Kerdi comes in. WIth a standard mud or thinset installation, the sub surface still gets wet. With Kerdi, being that it's a waterproofing membrane that sits on top of the mud of cement board, the only thing that gets wet is the tile and grout. And by a conventional pan on the bottom, do you mean doing a mud preslope, membrane, then mud again?, then thinset and floor tiles? Do I have this out of order or is there some other layer that needs to happen in there? no, you've got it right. OR, we could see just how good a mud mechanic he is, and see if he'll set and grout it the same time as he floats it the second time! :-) That's a TRUE (monolithic) mud job. *stirrin the pot* I got to proof reading this, and I had to add this disclaimer-- If he's doing thinset over the mud, that's the normal way it's done today, and there's nothing wrong with it, so don't get scared if he brings in the bags of thinset!! :-)
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I'm right at the same stage, and I had researched the issue obsessively because of seeing posts here and on the john bridge forum about how, exactly, the durock meets the flange (in my case on a Kohler shower base, but it seems very similar). Catmom posted about her husband's experience with the shower base, so you might search for that. It seems there are 2 approaches: fur out the studs as Kohler suggests, or notch the studs so the durock sits right above the flange. You also need to make sure the waterproof barrier (black plastic in my case) goes behind the durock, and overlaps the flange enough so it can get trimmed and then siliconed to the edge of the durock. I believe that the tile will extend slightly below the bottom edge of the durock, so you'll kind of curl the black plastic up behind the tile and sealing it to the flange. So far, my guys seem to have done it correctly. As for the second question, I think you just need to ask them to trim and remove the durock. I think they assume you want to tile all the way to the door frame, if I'm interpreting your photo correctly. I'm no expert, but I hope my explanation makes sense! Good luck today.
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I'm not sure if HB will bond to silicone. It may very well coat it just fine, but it might not "stick" enough to get the proper mil thickness. There's also the chance that it could stick during the application phase, but as the HB dries it shrinks a bit that shrinking could cause the HB to pull away from and separate from the silicon. If you really want to keep the silicon, I'd recommend calling Laticrete tech department and asking them. They're friendly folk. If it was me, I'd remove the silicon. Where you want a flexible caulk or sealant in the corners is on your tiled wall. Rigid grout will crack and can allow water intrusion behind the tile. Flexible silicon in the corners will move with any house settling/wall movement, and it'll keep the tile/grout facade intact. With a topical membrane like HB behind your tile, those corner cracks in the grout will be more cosmetic than anything else. But cracks in the grout can "hold" water and provide a start for mildew/mold, etc. Silicon in the corner can keep everything purdy and water-tight. You can get caulk to color match and texture match (sanded versus unsanded) your grout. This post was edited by mongoct on Mon, Sep 8, 14 at 14:51
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Millions of showers were made with wall tile directly applied to greenboard, no waterproofing of any kind. Cement board was viewed as a big improvement over that system because the substrate didn't fall apart when wet. Most of those showers lasted long enough to get to the expected lifetime of a bathroom and the next remodel. So it's not necessarily the disaster some here make it out to be. That said, appropriate waterproofing is another huge improvement and these days I'd find a tile setter who does it at the current state of the art. In answer to your question you really don't want yours to be the first that an installer does with a new-to-them system. Talk to your contractor and be prepared to pay a little extra if he needs to bring in a different sub.
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PRO
Creative Tile Eastern CT
6 years ago
100% silicone is not available sanded. Siliconized acrylic caulk is available sanded but is a inferior product. Grout manufacturers make their caulk/sealant colors in 100% silicone as TCNA requires but the majority of installers and DIY'ers are afraid to use it sacrificing quality to ease of use and saving a couple of bucks. Sad.
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PRO
Avanti Tile & Stone / Stonetech
6 years ago
Actually, it is. try http://colorriteinc.com/ I think the silicone sanded is ColorSil.
PRO
Creative Tile Eastern CT
6 years ago
Thanks for the link Avanti. I would now like to revise my previous comment to grout manufacturers do not provide sanded 100% silicone. There was a comment before mine that I was responding to as well as a comment after. Both have been deleted. Oh well. I gained knowledge so it was worth it to me:)
0
PRO
Avanti Tile & Stone / Stonetech
6 years ago
go to the link at the bottom of the page under grout/caulk. If they don't list it, you can give them the manufacturer of the grout and the number on the bag and they will custom mix it for you.
User
6 years ago
last modified: 6 years ago
color matched sanded silicone been around since the tile craftsman.

back in DA day pre interweb I used to make my own. Using Slower flash time silicone and mix it with sanded grout powder.

Not suggested for a first timer. :)
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PRO
Valley Tile and Plumbing
3 years ago
Anyone that uses backer board is not a real tile guy. Period.

A mud installation is the only way to go, Ever!.

Anyone who tells you different is selling you products, and a big lie.

Just use common sense. Screws... !!!

Really?Holding a "board"on 2x4s.. no wonder you have cracks! I'd be shocked if a backer board shower with a plastic sheet of anything for a pan... Lasts you for a year!

Where i live you are required to have a permit. #1. There are tests, and inspections prior to tiling... And after.

We use hot tar, or fabric reenforced waterproofing for the pan, benches, and niches...

And everything is set in metal lath reenforced cement!

This is the only way your shower will last forever.

Mud float vs cement board and waterproofing

MongoCT

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Creative Tile Eastern CT

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