Backbuttering mosaicsSometimes I  get asked how to backbutter mosaic tiles. I constantly have to tell people that you really don’t need to. There are very few instances when you’ll need to backbutter a mosaic tile. Normally if you feel the need to backbutter mosaics it is easier to simply use a larger trowel on your substrate.  

Backbuttering mosaicsIt is, however, a very handy thing to be able to do when needed. In the case of all these photos I chose to backbutter, or more pointedly put the thinset on the back of the tile rather than the substrate. The width of the niches these mosaics were going into was smaller than the size of my trowel, which makes it difficult to properly comb thinset on the back of the niche.

To backbutter mosaics simply grab a scrap piece of your substrate, in this case it was kerdi-board, and comb the thinset onto it just like you would if you were installing the tile to it.

Backbuttering mosaicsThen place your mosaic sheet into the bed of thinset and push it back and forth into the thinset, again, just like you would if you were installing it.

Once you get it bedded properly, peel the sheet of mosaic off of the scrap piece of substrate. You’ll have a sheet of mosaic with thinset fully covering the back of every tile in the sheet. You can then just install it wherever you need it. 

If you are using translucent, or semi-translucent glass mosaics, which is simply big words for stuff you can see through, be sure to flatten the ridges in the thinset first so they are not seen through the mosaic.

Backbuttering mosaicsThis works well in the back of niches, small areas that need mosaic, or anywhere else it’s difficult to stuff a trowel full of thinset into. It also ensures complete coverage if you are doing something like placing mosaic tiles on the ceiling of a shower.

In the few instances you actually need to have thinset on the back of a sheet of mosaics this is a very handy trick to have in your bag.

You can click on any of these photos for a full-size example of my horrible photography skills…


Backbuttering mosaics

Fully backbuttered mosaics

Backbuttering mosaics

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  • Chief Steve

    I want to thank you for this tip. I have been noodeling how I was going to be able to set my mosiac 1″ hex tile in the small space between my tub and the wall. It is a rounded corner tub and tapers to within 1″ of the wall, clearly to small for even a putty knife. I considered trying to cut notches in a plastic trowel, but I think this solution beats that approach.

  • Wendy

    Thank you, thank you, thank you! This technique was amazing to use in an area it was difficult to get a trowel in without making a mess everywhere. Every other website said to back butter with the trowel, but i found it was hard for me to do this without pushing a lot of grout through the mesh and up into the tiles. I am redoing my bathroom, and your site has been invaluable to me. Thank you.