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Pyohe 11-07-2020 11:10 AM

Waterproofing suggestions for tub/shower combo
3 Attachment(s)
Hi. I gutted my hall bathroom, and the plumber just installed my soaking tub and the plumbing for the tub and shower. Tub recommendation was 2"-3" of mortar. I have no idea if he went by the tub's instructions.

Even with the marble tile on the floor, it is not flush with the oak floor in the hallway. It is about 1" - 1 1/8" lower than the hall. If I removed the old marble floor tile, it would be even lower. I had planned to keep the marble floor, but the plumber tore up some of the tile that didn't need removed. I doubt I can match it. Plus, he mixed the mortar on it. The mortar is still on the floor because I don't know how to remove it without scratching the marble.

I plan on tiling the shower walls, but I need to decide on the easiest method of waterproofing for a DIY project. I know Kerdi has a membrane, and Mapei Mapelastic Aquadefense and Laticrete Hydro-Ban are liquid membranes. I am concerned about using the liquids incorrectly and leaving pinholes, air bubbles, etc.

My questions:

1. Do I need to wait until the mortar is dry to do anything? He had to move drain and plumbing lines, then set the tub in mortar.

2. Does the tub drain and overflow need tested for leaks before I do anything else? The rough plumbing is in, but no faucet is installed. I doubt I can test the overflow, but I could probably test the drain for leaks.

3. Is my next step leveling the walls and adding furring strips and adding 2x4s where I need them so I can attach concrete backerboard? One or two need added.

4. Then add bracing for shower doors and grab bars?

5. Then, do I tile the floor? I guess that depends on whether the marble needs removed first?

6. Can I tile over the tile? Can I use concrete backerboard on top of the old marble to make up the height difference? I assume that I will need waterproofing on top before I install thinset and tile. If I remove the old marble and use self-leveling mortar, I would need to use a lot, plus let it fully dry before adding more. That seems like it would be more expensive.

7. If I can tile over the tile, do I need to remove the mortar residue? Does the floor get tiled after the shower?

8. Would the Kerdi membrane be the easiest for me to DIY? Is there something else I should consider?

Thanks, and sorry for the long post.

BIGPHIL 11-07-2020 01:11 PM

Holy cow! Not sure what the plumber was thinking mixing mortar in there without adequately protecting your floor! How'd you let him get away with that!? I wonder if you have some grounds for legal action if he ruined your floor? I'll give my opinion on a couple of questions but I'll leave the others for the more experienced people.

2) Absolutely. As long as the drain and overflow are connected and the plumber signed off on them, I see no reason you can't pour some water down the drain as well as the overflow to test for leaks. Better to do it now before the walls are closed up.

8) As a DIY'er who has previously used a liquid membrane in a tub/shower combo, I'd cast my vote against that method. I'd vote for one of the foam boards like Wedi or Kerdi board. They're very user friendly. After adding up the cost for backer board and the liquid membrane, the cost for the foam boards isn't all that bad. My vote would be for Wedi as I just did a tub/shower with it and it was very easy to work with. As long as you follow the manufacturers instructions, all of the products you listed will work just fine. With Wedi, it's very important to get that 1/2" bead of sealant at all locations called for in the Wedi handbook!

I will also add that if your tub tiling flange is 1/4" or less and tight to the walls, assuming they're plumb and square, the 1/2" foam panels would be ok as you can properly create a notch with an exacto knife for that critical joint. If the flange is larger, say 3/8", I'd opt for the 5/8" thick panel to allow enough material to create a proper notch to the tiling flange. That or add some furring strips to the studs to bring the 1/2" material out a bit.

These are just my opinions so take them with a grain of salt. I only offer advice on aspects that I have experience in.

greenjp 11-07-2020 08:20 PM

x2 on the Wedi board. IMO the easiest and most foolproof system especially for an inexperienced DIYer. It's pricey but if you've got the tub in and the studs are good to go you can get the whole surround up in a couple hours and be tiling almost right away.

ss3964spd 11-08-2020 07:20 AM

Welcome back, Patti,

What is under the existing marble? Is the existing subfloor concrete or wood?

Seems odd to me that your existing tiles are an inch or more lower than the adjoining wood floor. While you might be able to tile over the existing marble doing so really depends on how well the marble is adhered to the floor, and those missing pieces will certainly present a challenge. And no, you'll not want to attempt installing cement board, or any other tile backer board, over the existing tile because those require the use of screws, and lots of them, to hold them down.

I cannot tell if that little short wall at the end of the tub was added as part of this remodel. If it was then I can see why the tiles were removed.

Davy 11-08-2020 10:51 AM

If the marble floor was going to be saved, it should have been protected from day one. Looks like you had done a lot of work in there before the plumber did his job.

I can't tell if the marble is green. Green marble is water sensitive and I have no idea if it will cause problems if you tile over it. I don't make it a habit of tiling over old tile but like Dan said it can certainly be done if it's bonded well to the floor. I would tap lightly on the floor in several spots with the handle of a screwdriver and listen for hollow areas.

Seems like you're wanting the easiest waterproofing system. If you're going to use cement board, unlike Phil, I see the paint on waterproofing pretty easy to install. There are many to choose from, you mentioned a few. Or, Kerdi over regular sheetrock can be used as waterproofing. Sometimes the best system for you is the one you can easily find.

BIGPHIL 11-08-2020 10:30 PM


Originally Posted by davy
Seems like you're wanting the easiest waterproofing system. If you're going to use cement board, unlike Phil, I see the paint on waterproofing pretty easy to install.

I never said it wasn't easy, but I will say I don't think it's as foolproof or as simple as the Wedi system for a DIY'er doing a simple tub surround. There are more steps involved in creating a water containment system using CBU than there are with systems like Wedi. CBU is typically heavier, harder to work with, and harder to cut cleanly as well. For a small tub surround, the cost would be nearly a wash.

Pyohe 11-12-2020 06:20 PM

2 Attachment(s)
Big Phil, I had mentioned to him that I wasn't sure whether I was going to keep the marble or build up the floor, but I guess he forgot. There was sheetrock dust on the floor before he got there, but that was it. I assumed he would protect the floors, and I never thought he would mix the concrete ON the marble floor. I have never seen that done. I cleaned up all the mortar he tracked on my carpets, rugs, and oak floors. He kept telling me to stop cleaning the wood floors because the dried mortar just wipes right up. If that was the case, I could wipe up dried concrete.

I looked at the NTCA website for tile contractors, and the closest 5 star contractor is 2 hours away, and closest non-5 star is 2 hours also. Three contractors within 250 miles! I have spent so much money paying new contractors to redo brand new work, and I have given up. I know I can do it myself with a little help and information. At least, I will read the manufacturer's requirements of products. My plumber refused to read the installation instructions that I handed him. He tossed them in the corner. Then he installed the tub his way. I had to push him to add the mortar underneath the tub like the manufacturer requires. I hate having to watch over or question people. He installed the tub, screwed the flange to the studs, built the pony wall, and left a gaping hole in the ground under the tub.
I asked him he was going to set the tub in mortar with the hole in the ground. He said he wasn't going to fill the hole or set the tub in mortar. This was how he left it. He came back the next day because he hadn't planned on filling the hole and he didn't have mortar with him. So, because he did not read directions, and installed the tub, then removed it again, then poured mortar and reinstalled it...it cost me more money because he billed me for his time. I gave him the instructions and told him I wanted to follow manufacturer's recommendation 100% so he knew in advance.

Pyohe 11-12-2020 06:56 PM

Greenjp, I have been trying to find Wedi products, but all I can find are shower kits. At that price, I don't want to buy things I don't need like the shower pan.

SS3964spd, the marble tiles have been there since at least 1970. Previous owners put them in every bathroom and in the kitchen. It took us a long time to get them off the kitchen floor. The tiles are on concrete.

So, I can't tile over them and I can't put something over the tile and add new tile. I guess they will need to be removed, but how am I going to make up that much difference in floor height? That would be a lot of self-leveling concrete.

Davy, I tapped the tile and did not hear any hollow sounds. I read today that the liquid membrane wasn't bad to work with, but the concrete board was pretty bad to cut and there would be lots of dangerous dust so we should cut it outside. That is just sheetrock dust and insulation on the marble floor. The plumber was two weeks late, and he gave me no notice other than ringing the door bell. The tile is black marble with white veins. It is pretty common. True, I will have to use whatever I can find locally, but I wish I could find Wedi.

How long will it take for the mortar to dry under the floor?

When should I test the drain and overflow?

When does the toilet flange get raised? Before or after I tile? The plumber said he would do it after I tiled the floor. Is that right?

Is there any other solution for the tile floor to save me from that demo? Maybe I could deal with the height difference.

Pyohe 11-12-2020 07:06 PM

I forgot one thing...

All of the studs are 16" apart except the ones where the plumbing is. Those two are 17" apart. The pex is in the way so I can't add a full vertical 2x4. Could I put a vertical 2x4 part way down, then nail to a horizontal 2x4, then put another partial 2x4 from there to the floor? Sort of like H.

I am still looking for a tile person, but I may have to DIY. We have a million dollar lakefront housing addition being built a few miles away, and they have taken all the excellent contractors for the last 3-4 years. Those are big jobs with a big paycheck compared to my small project. Can't blame them. My heat/air contractor said they are working late at night and on Saturdays at the new addition.

Davy 11-12-2020 07:18 PM

Hi Patti, if you're confident the marble is bonded well, you can tile directly to it. I like to rough up the surface using rough sand paper to help the new tiles bond.

The thinset under the tiles will usually set in 24 hours.

If you're going to replace the toilet flange, you can remove it before setting the new floor then set the new flange after the tiles are set and grouted.

Pyohe 11-14-2020 03:00 PM

Thanks, Davy. I will tap every tile again to make sure.

The new tile is 5/16" or 8 mm thickness plus the thinset, so that will not make up much of the difference in height. With the marble in place, the bathroom floor is 1 1/8" lower than the hall wood floor. If I remove the marble, it will be 1 3/8" lower.

The marble is covered in mortar so I will clean it up today. I have a feeling cleaning it will scratch the marble anyway, but I can scratch it up more. Some tiles are missing where the old cabinet used to be. Do I need to use self-leveling concrete there? And by the tub and pony wall?

If I tile over the marble, I will still be off by 13/16". What is the best solution? Besides learning to live with it? ;-)

The drying time I was asking about was the mortar that filled in the hole in the concrete slab under the tub where the plumbing lines were dug up. The tub was set in mortar too.

How long will it take it to dry under the tub so I can see if the tub drain and overflow leaks?


cx 11-14-2020 03:55 PM

Patti, by now the mortar under your tub should be sufficiently cured for you to test the drain plumbing. Presuming, of course, that he used some sort of Portland cement masonry mortar.

My opinion; worth price charged.

HouseOfJoe 11-14-2020 05:55 PM

Patti, in regard to the tub surround, I’m doing my shower project with the Schluter system and I was able to get everything I needed on Amazon. I found out later there was a local supplier that I could’ve gotten it from but as it turns out the price was pretty much the same. Perhaps Amazon has the Wedi system too.

ss3964spd 11-15-2020 08:35 AM

Patti, whatever additional studs you can add, vertical or horizontal, will help.

As far as raising the floor height goes, your options are indeed limited due to the concrete sub floor. The only option I am aware of is adding a mud bed. If you choose to do that remove the marble first so that the mud will be thick enough.

In fact, given that the old vanity area is devoid of marble, as well as that area near the half wall, I'd remove the marble regardless. But that's easier said by me than done by you. ;)

Pyohe 11-16-2020 11:25 AM

Thanks, CX. I took a picture of the front of the bag before the contractor threw it out.

It says, Ash Grove Pro Mix Masonry Mortar Type S. (Brown and white bag.) Meets ASTM C 270.

Thanks, HouseOfJoe, I will check Amazon.

Ss3964spd, I was afraid of that. I can feel my knees hurting already, and I have good knees even if they are 64 years old! My husband's knees are bad so this will be my job to remove the old tile and add the new tile.

My questions...

1. Once I get the old tile and mortar off, what should I use to make up the difference in height? Self-leveling mortar? Is that a mud bed? Will I need to use it several times and let it dry between each layer? Or pour it all at one time? Drying time?

2. How do I figure out how many bags to buy? The floor from the back of the tub to the toilet wall is 14.25 sf and the rest of the bathroom is 60 sf, but how deep will the concrete go in total? 74.25 sf + thickness...

3. The self leveling compound will cover up about 1.25" - 1.5" of the tub apron. Is that good or bad? In the future, will we be able to replace the tub if the concrete goes up that high on the tub apron?

4. With 1.25" of concrete added, will I need to do add lumber to the studs? The horizontal studs on the floors are only 1.5" tall. Should I double them between each vertical 2x4? I will need some of the lumber showing so I can nail trim molding. I could nail to the vertical studs, but they are all different widths apart, so I could use a stud finder, I guess. The original builder was "tape measure challenged"!

5. How do I decide if I have poured enough concrete? If my new tile is 8mm (5/16"), how thick will the thinset be?

6. When poring that much concrete, is it okay that it will touch the bottom wall studs? I know I need room for expansion and contraction.

7. Toilet flange... Install after the concrete and tile floor has been completed. The plumber said to leave the old flange in place, but he said to set CBU or exterior plywood in mortar, then screw it in to build up the floor, not concrete. If I use concrete, will he be able to remove the old flange and install a new one? How do I keep the concrete from going inside the toilet hole?

8. Should I do the floor first or should the shower wall board and the drywall go first?

Whew! So much to know! Thanks for your help. Patti.

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