Tiling a bathroom

zetti1102 · 08-01-2010, 10:45 PM

Hello everyone! I'm renovating my bathroom and was looking for some suggestions on tiling. I finished gutting the bathroom 2 days ago and replaced all plumbing also laid a new 3/4" plywood subfloor. The tub is going to be installed tomorrow and hopefully I can start the tiles within a week. I am going to install cement board on the floor and tub surround and have a few questions about it.
1. Should I bond the cement board to the subfloor? If so should I use a thinset (modified?) or is liquid nails good enough?
2. I would like to water proof it using ditra... I know I can install this on the floor but can it be used on the walls as well?
3. Do I use thinset or a latex mastic to bond the Ditra to the cement board?
4. Once the Ditra is installed, again would I use a thinset or latex mastic to bond the tiles to the Ditra?
5. Instead of Ditra, would the RedGard waterproofing be a good choice as well?
Any input on this would be greatly appreciated!

JazMan · 08-02-2010, 12:04 AM

Hi Zetti,

1. Absolutely no construction adhesive. You must apply a thin bed (usually 1/4x1/4 trowel), of thin set under all cement backers then fasten and tape the joints. What brand?

2. You can use Ditra on floors, then apply Kerdi Band on all seams and flash up the walls a bit. It's still not going to be completely waterproof since you can't treat the doorway, the floor/tub joint and the holes in the floor for toilet, etc. If you go with Ditra, you don't need the cement board. You can install more plywood (3/8 underlayment grade min. or thicker), then Ditra over the plywood. Cement boards do NOT make the floor stronger, more plywood will.

3. Never use any pre-mixed product with Ditra, Kerdi, on any floor or any wall that may get damp. Use thin set mortar only. It comes only in powder form. If on plywood, use modified. If on concrete, use unmodified. Install all tiles, (including porcelain) with a high quality unmodified.

4. Again, a good unmodified mortar to bond all tiles to Ditra.

5. Redgard can do a good job if applied correctly. Most of the time it is not. You need a certain mil thickness as directed. Most people just apply a coat or two and since it's red, they call it good enough. Ditra and Kerdi are much better and have different functions.

Jaz

zetti1102 · 08-02-2010, 09:35 AM

hey Jaz.
1. I'm going to use Durock board, do I use a modified or unmodified thinset to bond the durock to plywood?

2.The guy at the tile store gave me a premixed glue (I don't know exactly what kind it is I'd have to check it when I get back) and he said it was the right product to use in a bathroom. Im pretty sure he also sold me a powder form of latex mastic. Now I am a little confused on which "glue" should be used on the floor and which on the walls.

3.Since you say i cannot waterproof the room completely.. will i be risking and damage by not using the ditra. I have looked for the kerdi system but cannot find it in my area. I have visited a few local tile shops and a couple home depots but no luck.

rusty baker · 08-02-2010, 01:32 PM

Never, ever use mastic on a floor.

racebum · 08-02-2010, 04:37 PM

home depot should have ditra on the shelf and can special order kerdi

zetti1102 · 08-02-2010, 04:55 PM

Ok I looked at the materials the guy at the store gave me... the powder is a "polymer modified thinset mortar" and the premix is "dual purpose high performance type 1 ceramic tile adhesive." My wall tiles are ceramic and the floor is porcelain.

Bud Cline · 08-02-2010, 09:05 PM

zetti you are becoming "over-informed" and confusing yourself maybe.

First of all as already stated...all of the Schluter products are available at all of the Home Depot stores. Some of it is special order but they have it all.

Durock can be installed with either modified or unmodified thinset, unmodified is less expensive and preferred under cement board by the Tile Council of America.

Premixed mastic should never be used on a floor, doesn't matter what the maker says, it's never a good idea. Mastic is a higher profit-center for retailers by the way so they like to sell it.

Unmodified thinset can be used to install the tile over Durock and is mandated over DITRA.

If the tub surround is also a shower then use the modified thinset mortar they sold you.

Return the mastic, it is basically usless for your applications.

Porcelain tiles ARE ceramic tiles.

JazMan · 08-02-2010, 09:51 PM

Zetti,

It has become popular to use unmodified thin set under cement boards for floors. As far as I know only Hardie & Util-A-Crete suggest unmodified mortar under. (Hardie says either) All the others want you to use modified under their boards. All want you to set tiles with modified.

I don't disagree with using unmodified under the board, since it would make it much easier to remove everything at some later time when it's time to change things. I always followed directions and used modified under and above. I've also said that the customer should not call me in 20-30 years when it all has to be removed. That would not be fun. Of course I've been using Ditra for over 10 years now.

The guy at the store who sold you the pre-mixed stuff is not your friend.

Bathroom floors are rarely, and do not require waterproofing. However I recommend Ditra, and so you'll get partial waterproofing and uncoupling too. Tub surrounds do not require waterproofing either. But, I recommend it and use Kerdi if the client will pop for the xtra $200. Money well spent.

Jaz