Felt Paper, Plastic Sheeting or RedGard???

[Murphy_Smith]

So I have spent the last couple of weeks reading about how to prepare a bathtub surround to put up tile or stone. We currently have a basic white 4"x4" ceramic tile that just looks cheap. Planning on going back with a travertine stone which we have a lot of on the floors of the house.

I am going to start the demo of removing the old tile and backer board this week. My first question revolves around what type of moisture barrier to use. My understanding is that you can us 15lb felt paper or 4mil plastic sheeting underneath the concrete backer board. You can also paint a coat of red guard over the backer board on installed. I also understand that it is a no-no to do both b/c you can create a moisture sandwich. Only one of the walls is an exterior wall in this project. What is best method for creating a moisture barrier?

I plan on using shims to allow the backer board to mount over the bathtub lip without it bowing out and also plan on using fiber tape and thinset at all the joint.

Thanks for your help - this site has been a tremendous amount of help so far.

[bbcamp]

Murphy, what is best for you may not be best for someone else. I can tell you the advantages and disadvantages of each method and let you decide for yourself:

Advantages:

Plastic sheet/tar paper: Cheap, fast, readily available materials, simple method.

Redgard: Keeps water out of the backerboard so shower dries out faster, can handle odd shapes and horizontal surfaces, bonds to tub for continuous waterproof barrier.

Disadvantages:

Plastic sheet/tar paper: cannot do niches or horizontal surfaces, can trap water in backerboard where sealed to tub, heavier tarpaper or plastic can be a pain to fold around corners (smaller sheets and 6 inch overlap helps).

Redgard: fairly expensive, takes time to cure, each coat must be checked for minimum thickness, voids in coverage may go un-noticed and become leaks, corners must be reinforced with fabric which creates small lumps in surface.

In either case, the vapor barrier on your exterior wall insulation must be defeated with cuts or removed.

[Davy]

I've installed hundreds of tubsurrounds with 15lb felt behind the substrate but one thing that really helps when using Redguard on the surface is it keeps the CBU from drying out your thinset too fast. Raw CBU sucks moisture out of the thinset and you really have to move fast and have everything prepared before spreading. Although, I wouldn't be taking a coffee break with thinset spread over the Redguard, you do have more time to get the tiles set and adjusted. But, if you do decide to use felt paper, use a garden sprayer to wet down the CBU several times, it will help you out. And with 12x12 travertine, either spread and set each tile one at a time or if you spread thinset on the wall, just do a piece or two at a time until you get going good.

Put a level on the tub ledge and find the lowest point. With 12X12'S, measure up 12 1/16 (thats one tile and one grout joint) from the low spot and draw a level line around from there on all three walls. Either nail a ledger board there and start on the second row or go ahead and cut in the first row up to the line.

[Murphy_Smith]

We are planning on putting a niche in the shower and would like to go with a premade that we can tile over such as the product my noble.

It sounds like I can do both felt and Redguard and I am fine with that. I just want to confirm that it will not create this "moisture sandwhich" i keep reading about.

[bbcamp]

Either/or, Murphy, not both.

[Murphy_Smith]

Thanks for helping me Bob.

I will go with Redguard. I spent about 10 minutes on the phone with them and they walked me throught it and suggested a two coat application.

[bbcamp]

Suggested? Here's what their data sheet says:

After the first coat turns red, inspect the film for integrity
and fill any voids or pinholes with additional material.
Apply a second coat at right angles to the first coat.
Periodically check the film thickness with a wet film
gauge. Combined dried coatings must be at least
30 – 35 mils thick. When wet, the combined coatings
must be at least 60 – 70 mils and must not exceed
125 mils wet film thickness.

Pay attention to where they talk about the "weet film thickness gage." Important $5 tool, that.

[Murphy_Smith]

I should not have used the word suggested.

I am going to do 2 coats and will pick up a mil guage as well. I would assume that if my first two coats are not enought to stack up to 30-35 mills thick - then I could always add another coat till I get there.

I am going to pick up a mil guage tonight.

Again thanks for all the help. We are headed to the stone store to look at some travertine this evening.

[Murphy_Smith]

So I have made my descicion that I am going to go with a 1/2" Durock backer board and redguard moisture barrier.

Please give me some guidance as where to mount by durock in relation to the tub flange. My understandsing is that you want to leave a 1/4" from the top of the flange to the bottom of the Durock. Is this correct.

I have also read about people using 1/4" shims muoting the backer board so that it is 1/4" off the top of the tub. My only concern with this is if I add a 1/4" spancer then my tile will be 1/4" off the drywall where it meets one outside the shower.

please advise

[macgyver_ga]

Shim out the entire wall. Then your backer board and drywall will sit flush with one another.

In my current bathroom remodel, I shimmed one wall out 1.25" and the other 0.25". I did this so I wouldn't have to rehang my door frame on the .25" wall.

[Murphy_Smith]

I guess I will have to see how the heights line up once I remove the tile and exsisting backer board.

I am not opposed to shimming it

[cx]

Murphy, 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. We can give it a more generic title any time you'd like.

If you're using a moisture barrier behind your CBU you can get away with mounting your wallboard above the tub's tiling flange and having the moisture barrier lap over the flange into the tub.

But there are those of us who think the wallboard should always lap over the tiling flange and stop just short of the top of the tub. And that's expecially true when using a liquid applied waterproofing membrane on the drain side of the wallboard.

Matching the new wallboard with the old is a different consideration and can be handled in a number of ways if the joint is not flush.

My opinion; worth price charged.

[Murphy_Smith]

CX - thank you for the advice.

This weekend we are going to demo the tile and backer board and get a new shower valve installed.

I am going to do another thread with pictures as the process evolves.

Thankss

[bbcamp]

Keep everything right here, Murphy.

[Murphy_Smith]

will do