There are numerous really cool mosaics and liners which can be installed as an accent into your main field tile to add a unique touch to an otherwise standard tile installation. These are products such as glass and natural stone mosaics, individual painted tiles, or custom accents.

The biggest problem with these, however, is they are oftentimes not the same thickness as your main tile – they are usually thinner. This is especially true of most glass mosaics. I usually solve this problem with Schluter Ditra. Although I use ditra as my example in this post, you can also use regular 1/4″ backerboard if your inserts are significantly thinner.

glass mosaic insert

Photo 1

See that glass (and metal) mosaic right there? (Photo 1 – You can click on it for a size larger than a small dog) It’s setting inside the main linear mosaics I’m installing on a backsplash. See how much thinner it is than the surrounding tile? That’s what we’re gonna fix. When you have your tile installed you want it all to be on the same flat plane without either tile sticking out (or sinking back). The best way to do this is to have an additional substrate behind your thinner tile to bump it out flush with the rest.

You want to cut your ditra about 1/16″ smaller than the overall size of your insert. You want to make sure you have enough support behind the insert, but you don’t want it larger. (Photo 2)

glass mosaic insert with ditra

Photo 2

glass mosaic insert with ditra

Photo 3








In Photo 3 you can see where I’ve flipped the ditra upside down so the fleece side is out. You want to install your insert onto the fleece side rather than the plastic, dovetailed side. this is much easier, especially with smaller tiles, and gives the insert more adhesion on the backside once installed. The thinset will ‘lock’ it to the wall doing it this way.

Photos 4 and 5 show how the ditra bumps it up to the same height as the field tile. If your insert is a LOT thinner, it may be better to use the 1/4″ backerboard, although you can double-up the ditra to make it thicker.

glass mosaic insert with ditra

Photo 4

glass mosaic insert with ditra

Photo 5








Once you get your ditra and inserts cut to size (cut all of them at once) get your thinset mixed up and cover the entire fleece side of the ditra inserts. Make sure the entire surface is covered, most mosaics are fairly small and any uncovered areas may lead to just one or two pieces not being adhered well. Spread it just like these here:

glass mosaic insert with ditra

Photo 6

glass mosaic insert with ditra

Photo 7









Then place your inserts onto the ditra and press down slightly – only slightly! Before you firmly press the inserts and the ditra together you want to flip them upside down. Doing this ensures that the face of your inserts, the shiny part that makes people go ‘ooooh, pretty’, is completely flat. Flipping them upside down, then pressing down firmly, will get the entire face totally flat and get a full bond onto the ditra. It is always best to use a flat surface on the back, squeezing them between the flat surface and the flat countertop or bench – whatever your wife lets you use. Like these:

glass mosaic insert with ditra

Photo 8

glass mosaic insert with ditra

Photo 9







Once you get them all installed to the ditra, flipped, and pressed down firmly to ensure a full bond – leave them alone! Give the thinset at least three hours to cure and get a grab, ideally let them set overnight. Really, leave them alone. Stop staring at them. Go have a beer Pepsi and have some dinner. We’ll get to them later.

glass mosaic insert with ditra


Once the thinset is cured you can fill the dovetails with the flat side of your trowel, then comb on the thinset with the notched side and install them into your design. You can cut your main field tile with spaces large enough for your insert (don’t forget the measurement for the grout line around the mosaics). And tile away. When you’re finished you should have two different tiles, with different thicknesses, installed flush on the same plane. Like this here:

glass mosaic insert with ditra


This method works for backsplashes, shower walls, even tile floors. As long as you have good contact with the insert to the ditra, and good contact behind the ditra to the substrate, you should have a nice, flush tile installation which makes people go ‘ooooh, pretty’. Like these here:

glass mosaic insert with ditra

Ooooh, Pretty...

Porcelain backsplash tile installation with glass mosaic inserts in Fort Collins, Colorado

Ooooh, Pretty < See?


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  • Jonathan

    Hi Roger and thanks for,
    First one observation:
    Your photo #3 seems mostly necessary for the same reason that Schluter tells us that the smallest (recommended) tile size to be used with Ditra is about 2″ x 2″ (when the tile is being attached to the ‘waffle’ side of Ditra). And it seems your example has smaller tile than 2×2″.
    Now my question:
    1) Background of the project.
    I’m tiling a bath with 8×8 and 12×24 field tile. Their thickness is 9mm. Except around the perimeter of the tub and shower pan (both one piece, enamel on steel with 1-1/2″ vertical tiling lip), At the perimeter I’m using 2×6 bullnose and some extra 3×6 (Daltile Restore Bright White [from that orange box]) that are 6mm thick.
    The backer board is GP DensShield. Tub and shower pan are installed per GP instructions with the DensShield extending down over the tiling lip and leaving 1/4″ gap above the deck ( shown in illustration DS003).

    Silicone caulk is used to fill the gap under the DensShield. Consequently, the grey textured face of DensShield is the waterproof barrier plane.

    2) Actual question.
    If I install (3mm) Ditra on the DensShield (waffle side out to tile) to level out the 6mm and 9mm tiles, is there a preferred mortar to use on the fleece or waffle sides? I have Bostik Ditra-Set I’ve already used to install 400 sq ft of floor tile and Bostik Big tile and Stone (BBTS) to install the bath field tiles.
    Is the non-sag of the BBTS of much importance for the small perimeter tiles?
    PS – This is my first time setting wall tile.
    Also, how can I attach some photos?

  • kelly

    Hi Roger,

    I am tiling around my fireplace and need to raise the level of the wall about an 1/8″ or so in order for the tile to plane out against a metal trim piece framing the firebox. I was going to put ditra on the wall just as I would on the floor (fuzzy side on the drywall and the waffles facing out). But after reading your post about using ditra “upside down” in order to get glass inserts to plane out with tile, I’m not sure which side to tile. I was thinking of adding a few screws to insure the ditra is really stuck to the drywall, but if I use it upside down that may not be necessary. What would you do?

  • Allen

    So…If a person were to discover a dip in a floor after the Ditra-Heat, heating cable, and some tile over the cable (but in an undipped area of the floor) were installed, would using a strip of Ditra-Heat in the lowest area be a reasonable solution? If so, face up or face down? The dip might, in theory, extend over 32″ with the middle 16″ being the depth, more or less, of a piece of Ditra-Heat. Dogs are sleeping in buckets of water while we await your response. Thanks!

    • Roger

      Hi Allen,

      Yes, you can fill that with a strip of ditra heat provided the dip is lower than the height of the ditra (but you knew that). It doesn’t matter which way is up, it should be encapsulated in the thinset.
      I would install that strip and level out the area with thinset, let that cure (at least a little bit so you’re not pulling it out while spreading thinset over it for the tile), then install the tile over it.

    • Allen

      Would this scenario be more interesting with D-H Duo?

      • Roger

        I don’t understand what you mean by that. What would be significantly different?

  • Don

    I have a question, what is the best size trowell to apply mastic to kitchen walls for a glass backsplash? They are in 12×12 interlocking sheets. I came onto a job and a subcontractor was using a 1/16″ trowell to apply. Thanks your your time

    • Roger

      Hi Don,

      You don’t use mastic to install glass. Mastic will never fully cure behind glass. You need to use thinset.

      That said, if the substrate is flat you can use a 1/4″. A 1/16″ trowel isn’t used for anything but VCT.

  • Jodi

    I am a mosaic artist and work with many differing tile and glass thicknesses. It is a major pain trying to level all the varying dips and bumps during installations. I have been trying to find an easier solution, this way of using ditra could be a real time saver for me. But when I went to buy it the salesperson said it was strictly for floor installations – I do wall installations. Any advice? Or should I ignore the salesperson!

    • Roger

      Hi Jodi,

      Ignore the salesperson. I have used it on MANY wall installations both inside and outside of showers.

      • Jodi

        Great! I am attaching to concrete wall, so would I use unmodified thinset to adhere my mosaic to the ditra fuzzy side and modified to attach the waffle side to the concrete wall? Also, how long must I let the mosaic cure on the fuzzy side before attaching to the concrete wall?

        • Roger

          You can use modified or unmodified for either. If it were me I would use modified for both, although either will work. 24 hours is normally plenty for a cure before moving them around.

  • wendy

    What about the inverse problem? I want to set some beautiful 3/8″art tiles in a field of standard subway tiles. So the accent is too high. I considered getting some kerdi board and digging out wherever the 4″ tiles would go. Is there a more elegant solution?

    • Roger

      Hi Wendy,

      There are a couple of solutions, the easiest would be to either get some additional 3/16″ kerdi-board and install it behind all the field tile. The less expensive solution with kerdi-board is to cut out the portion on which the insert is being installed, install it directly to the studs and shim up everything behind the field tile.

  • Belinda

    Like your photos and descriptions for getting insert to same height as field tile. How did you decide where to place the accent tile in the backsplash. I’m wondering if a similar layout, instead of a horizontal accent band, would work for a shower wall.

    • Roger

      Hi Belinda,

      I choose the locations of those types of accents depending on the design balance of the particular layout. Where the outlets are, the height of a given area, etc. It’s a personal taste thing and there is really no right or wrong. Basically whatever ‘looks’ right.
      Yes, it works well in a shower also. I’ve done it several times.

  • John McCaffrey

    Hi! I bought your wonder-guide for building a water-proof shower with Kerdi, but there is one important detail I couldn’t find in there. For both my shower base and my tub (I’m doing both) have flanges at the wall face that stick out about 1/4″ (the base and the tub are both screwed to the studs through this flange and then through the drywall). I can run the thinset down to the flange, run the Kerdi over the flange and silicon it down, but when I go to start tiling, there is going to be this 1/4″ bump (slightly less because of the layer of thinset) that is going to tilt the bottom tiles. What’s the bet way to deal with this – just fill the gap with thinset and have a slight tilt of the tiles at the bottom of the wall above the shower base and the bathtub? Thanks, John

    • Roger

      Hi John,

      It sounds like your tub is installed incorrectly (and the shower base as well, if it’s the same). The tub should be butted against the studs, screwed through the flange (actually, there are clips available to properly fasten the flange to the studs without screwing through it), then the drywall is run down to the top of the flange. If your tub and base are butted against the drywall it’s incorrect.

      That said, the best thing you can do it either add a layer of 1/4″ drywall or backer over the existing drywall, then install your kerdi. Or run the kerdi down as you describe and have that tilt at the bottom.

      • John

        Hi Roger, Thanks – you’ve given me a few ideas. I didn’t do a very good job of describing the problem. The tub is meant to be scred (or clipped) diredtly to the studs. The problem is that the space my builders left me with is 5′ 1″ wide, so I have 1/2″ at each end of the tub (the back wall is fine). I was thinking about adding a 1/2″ X 6″ plywood board all around the 3 walls of the tub, but it creates just the problem you describe – it’s like the tub is installed incorrectly. Possible I could add a 1″ floor-to-ceiling wall at one end (or 1/2″ at each end)- that may be the best bet. What do you think? Thanks, John

        • Roger

          Oh. :) In that case adding a 1″ wall to one end would likely be your best option. Or, if you those end walls are not part of another bathroom wall (the end walls both stop at the outside of the shower) then you can just add an additional 1/2″ substrate over what you currently have.