You can use the blue drywall outside the shower area, but there's no need for it behind Kerdi. If the Kerdi is properly installed, no moisture will get to the drywall anyway.

With 1x1, the toughest thing to overcome will be the build-ups caused by the overlaps of material. Some installers have gone to the use of liquid waterproofing for that very reason. One way to lessen the effect of the build-ups is to skim-coat the surface of the Kerdi from the corners so that it's more of a gradual buildup instead of just over a couple inches.

To gauge the size of your cut pieces, lay out the tile on the floor like it would be on the wall to get your measurements. But it's going to be tough with a 1" tile to avoid having small cut pieces. Some of the other guys might have better suggestions on that.

Now I'm freaked out about the overlaps. I understand the skim-coat option. Are there any other possible tips/tricks to help with this? The tiles are 1x2, not 1x1 but I don't imagine that matters much.

What size trowel should I use? The tiles are marble with paper-mesh backing. Should I deliberately apply the mortar thick in the non-overlap areas to make sure the overall install is even?

Doing a test layout of the tile is a great idea. I can't believe it never occurred to me.

For my niches, I'm thinking of doing the rough-build deliberately too large, applying the kerdi, then building up the niche so it lines up nicely with the tiles. If I need to do a large (1/2"+) buildup, I was thinking of using blue-foam insulation stuck into the mortar. Does this sound reasonable?

Thanks again. I'm getting close to my project start.

Can anyone help me with my last few questions?

Basically:

1) I want to avoid bumps in my 1x2 subways where my ditra overlaps. Any tips? Should I apply the thinset thick in the non-overlap areas?

2) If I skim-coat with thinset and let it dry, will the next layer of thinset bond to the dry thinset?

3) Does anyone see any problem with me using blue insulation foam to help build up my niche to make a perfect fit with the tile? The foam would be embedded in thinset, on top of ditra.

4) Finally: Anyone want to recommend a trowel size?

Please help!

1. You obviously meant to write Kerdi, not Ditra. Apply the thin set uniformly. Use a wood beating-block or a rubber grout float to beat tiles in.

2. Yes, you can skim then go back with the bond coat.

3. I guess that would work.

4. For Kerdi the recommendation is now 1/8" square notch. The old spec was 3/16x1/4" V. The trowel for your tiles can be similar to the Kerdi, or maybe a bit larger. All depends on how thick they are.

Jaz

Thanks Jaz,

The mosaic tiles are marble, and are relatively thick: 1/4".

I almost always do my niche bottoms with 3/4 inch counter top stone. If you have a counter top place in your area they will usually have a garbage can full of scraps. If you are lucky you will find a piece of marble to match yours. That way it does not really matter how it lines up with the tiles.

Ok - on to the next question. I've attached two photos of my marble tiles.

They are 1x2 subway in a brick-pattern.

How do I stick these on the wall? I sort-of assumed I would put them up interlocked, but the mesh will get in the way. Do I instead put them on the wall lined up (like in photo #1) and then go back and fill in all the missing tiles?

They also seem to have both a mesh and paper backing. I assume I leave both on?

Thanks!

Spacecadet, Your photos will not show up as you have posted them.

You can either host them to an imaging site or use the web site forum under "Post PHOTOS of the project you're having trouble with"

The mesh backed tile should not have any mesh getting in the way. The sheets are interlocking. Separate pcs will have to be placed at cut outs or end of walls etc.

I have never seen subway tile with paper backing. Usually paper or clear plastic is only on the face side of some mosaics.

I've run on to a few of those. The paper is usually wax-coated and placed on the back of the tile sheet to keep the mesh from "imprinting" the face of the tile below it during shipping.

Ok, let's try the photo's again. Kinda weird, the download links worked fine when I composed the message.

Marble Tile 1

Marble Tile 2

Hopefully it works this time. As you can see in the photos, the tiles can't interlock with me removing some of the mesh first.

The second photo shows the backing. The paper backing is attached to the tile, with the mesh then attached to the paper. So, in the box the mesh will contact the face of the tile below it. The mesh is somewhat "stuck". Perhaps the mesh is protecting the tile below from the wax on the paper?