Hi,

I'm going to be re-doing my existing tub/shower area as part of a complete bathroom reno.

I'm planning to use kerdi on the walls of the shower. Even though I understand it's not necessary, I thought I would use fiberrock behind the kerdi. Mostly, I'm worried about some water getting into the wall where the fixtures stick-out, so I figure if some water does get in then the fiberrock will stand up better.

I'm not planning on tiling the ceiling - I'm going to paint that. I also intend to use fiberrock on the ceiling. In this case, I believe the fiberrock will paint better than CBU.

Questions:

1) Is it ok to not tile the ceiling? I'm used to showers being 100% tile. Note: The shower head will be vertical mount down from the ceiling.
2) I know that a vapour barrier is not necessary behind the walls (because of the kerdi), but what about on the ceiling?
3) Will I have any trouble painting the fiberrock?
4) Do I need to mud/tape the fiberrock walls? (ceilings, obviously yes).
5) How good is fiberrock? Is it impervious to water, or just resistant? Is there another paintable option that I should consider?

Bonus Question: I've read a lot of posts on this board about using mortar, or spray-foam under a tub. I've also heard people say you don't need anything at all. Can someone sum this up for me? My tub is a 60" soaker tub. It's an above-floor-rough type tub. I want to do the right thing but I can't figure out what that is.

Thanks!

When you buy a kerdi drain now, you get a couple of extra items now: two rubber rings surrounded by two inches of Kerdi. One is made to fit around the shower valve, the other around the shower head supply.

If you didn't get these with your drain, you can order them. Of course, in your case since the shower head is coming from the ceiling, you won't need the rubber ring for the shower head.

Having said all that, there is really no reason to waterproof anything above 6 1/2 feet. No significant amount of water will get that high. The last shower I tore out was built with green board and the highest moisture I found was about three feet from the floor.

You can tile the ceiling if you want, it's not necessary. A good quality paint on the ceiling will protect it just fine. Save your money on the fiberock and get drywall. It's easier to install, cheaper, and fiberock is only water-resistant anyway. Trust Kerdi to do its job and don't worry about it. You don't need a vapor barrier in the ceiling.

For your tub, you should check with the manufacturer and see what they require for support. If you can give us the make and model of it, someone on here that is familiar with it might be able to tell you what is required.

Hi, thanks for the reply.

Just to be clear: It's a tub+shower combo, not separate. I don't think that will affect your answer at all, but just in case. What this does mean is that I haven't bought a shower-kit, I'll be buying Kerdi by the ft and installing it.

I'm not planning on buying any of the pre-made corners/edges or anything either. I've *assumed* I will be able to make all the corners with the regular stuff.

This is the tub: http://www.azzurabath.com/single_product.php?Class=5FT%20BATHTUBS&Model=BO64

The install guide doesn't specify much in this case.

I'll comment on the Fiberock. Seriously, putting Kerdi over Fiberrock is a real pain in the bum. It sucks the moisture out of the thin set so fast, you end up having terrible contact between it and the Kerdi. Drywall is much much easier. And..as Kman said...you can buy those rubber sealent rings separately. If you caulk around the cover plate, you won't get any water behind anyway.

As Kman mentioned ... check with the tub manufacturer, but never allow the weight of the tub to sit directly onto the tiled deck.
I always support the tub legs with assorted thicknesses of plywood and then squeeze in the foam just to help support and keep everything in place (put water in the tub first)
If your tub has rails, then I use plywood and shims at the ends of each rail to level and support the weight .... then pack mortar under the center of the rails.

I too do not recommend Fiberock as your CBU for the reasons mentioned. It really sucks.....moisture. You are supposed to use regular wallboard per Kerdi directions, works perfectly!

The tub installation is very important, follow every step in the directions. Pay special attention to the "tile lip extrusion" detail, I hope you have that.


Jaz

Ok, thanks everyone. I've officially abandoned the fiberrock and I'll just use good-old-drywall (1/2").

Bri: I'll caulk around the goof-plate, but what I;m worried about is water wicking down the grout behind the plate. Shirley some must get in there? Maybe I worry too much.

As for the tub, maybe I'm confused: Is everyone suggesting that I put mortar or foam under the feet/rails just to make sure they have good contact with the subfloor? I guess that makes sense - but what I thought people were suggesting was basically filling the entire cavity under the tub with foam/mortar so the tub itself doesn't flex with weight. I've been told it makes the tub feel more solid. Comments on this?

As far at the hole for the cover plate is concerned, there are a few things you can do. Sometimes I will leave the Kerdi over the opening...just leave the hole for the tap and the screws. OR...cut the drywall so it bevels downwards(bottom of hole) and then coat it with silicone. Any water reaching there, will not soak into the drywall and will drain out instead of in. I usually use my liquid waterproofing instead of silicone...but then I have a 5 gallon pail of the stuff.

Mortar works great ... just be sure to support the tub until it sets up. Shims are helpful under the legs or rails until the mortar sets.
If you want to use foam, use it to assist keeping everything in place ... it help insulate the tub .... it does add some support under the main body of the tub (not under the feet or rails).

Ok, just to make sure: It's probably a good idea to use the blue drywall (for humidity resistance?) instead of regular drywall throughout (including behind the kerdi). Yes?

While I'm at it, some more questions for this project:

I'm going to be tiling with 1x2 polished marble subway tiles. Any tips? I was thinking of buying some sheets of 1x1 as well so I can use them to fill in the offset where I start the 1st sheets against a wall. Make sense?

I'm also planning on building a few niches, and want to make sure that I don't end up with sliver-sized tiles at the top or bottom of the wall. Any tips here? Do I need to actually stick the tile up on the wall to do a rough layout? Or can I rely on my 12x12 sheets to be actually 12x12+1/4" grout along the outside and work completely off measurements? I assume I should start at the bottom of the wall where the tub is?

Thanks a lot. This forum is simply the best thing on the internet for quality advice.