This post describes how to hide mosiac tile seams, especially for shower floor installations. You really don’t want a seamy tile installation to ruin an otherwise great custom tile shower design. Stone mosaic tile in particular can often end up really seamy without some expert care and attention to detail.

Mosaic tile (whether ceramic, glass, or stone) comes in 12×12-in mats of tile glued on plastic mesh. This makes it possible to install mosaic tile quickly, since it’d take forever to install each individual mosaic tile by hand like this:

These mosaic mat tiles are sometimes glued to be almost perfectly uniform, so that every mat is completely identical to every other. More often, individual mats will vary a bit and therefore not fit together perfectly. This is why ANY mosaic tile install requires carefull planning for a perfect result. You have to dryfit EVERY tile mat beforehand to prevent seamy results.

This is especially important for ‘natural’ stone mosaic tile. These tile mosaics use sandstone or other sedimentary rocks that have been machine cut, honed, and glued onto 12×12 -in mats.

Mosaic tile mats are designed to fit together like a jigsaw puzzle where every piece (ideally) fits seamlessly with any other piece. However, real world results can vary from this ideal.

Upsides to using stone mosaic for a shower floor

There are several reasons why natural stone mosaics are popular for shower floors. First, the mosaic patterns usually leave lots of area for grout, which makes for a nice slip-resistant floor surface. This is great for safety.

Second, it’s an attractively trendy design based on the number of installs that I’ve done in Austin the past few years. Home buyers and designers here in Texas seem to really like the natural rustic look that stone pebble mosaics give. Here are some examples:

And third, there are lots of different stone types and colors/shades to choose from. And any choice will have lots of natural color variation. This makes stone mosaics easy to coordiate with just about any wall or trim tile.

Downsides to pebble mosaic shower floors

There are however some drawbacks to using stone mosaic tile for a shower floor. First, pebble mosaics can be pricey. Even the least expensive mosaic mats that will fit together well can cost $25-ft2.

Second, you need to treat any natural stone tile with a good penetrating sealer before grouting. This is NOT for waterproofing, since no sealant will make shower floor tile and grout waterproof. This will however prevent a permanent grout haze from sticking to the porous stone’s surface and causing discoloration when grouting. This adds an extra install step and therefore a bit of added labor expense. You don’t however need to spend a lot for the sealer or use industrial-level toxic junk. Just a quart of a good basic water-based stone tile sealant is more than enough to get great grouting results for even a large stone shower floor.

Third and most important, specific brands and styles of stone pebble mosaic mats can be difficult or sometimes even impossible to install with a completely seamless finish. You don’t want mosaic tile seams to show.

Consider your tolerance for seeing seams!

Expensive stone pebble mosaic mats can usually match up pretty seamlessly with any side of any other mat. This is because more expensive mosaic tile generally (tho not always) has more precise manufacturing, with tighter tolerances. For example, more precisely cut jigsaw pieces will fit together better. This gives maximum flexibility for matching mats together to minimize the appearance of seams. You have lots of options for (ideally) seamless matching if each mat can be rotated 90, 180, or 270 degrees.

Less expensive stone pebble mosaic mats are often much less precisely glued down. Also, they often have only two sides that can match with the layout pattern of an adjacent mat. This cuts down on manufacturing costs but also really limits your options for eliminating mosaic tile seams.

The bottom line

More expensive stone pebble mosaics are usually better engineered and manufactured with higher quality controls. As a result, the more expensive mosaics will generally fit together better and therefore show fewer seams when installed and grouted.

So if you’re on a tight budget and can live with seeing some seams in your shower floor, then go ahead and shop for discount stone pebble mosaic options. You can still minimize seaminess by shopping at a discount tile store like Floor & Decor that has liberal return policies. This trick lets you buy double the amount of mosaic sheets that you’ll actually need, so that you can experiment to see which will actuall fit together best and then return the rest.

However, if you’ve got some OCD tendencies or are wanting to use a really contrasting grout color for your shower floor, then budget $25-ft2 minimum for premium stone mosaic floor tile that’ll have the best chance for fitting together best. Also budget for a true craftsperson labor cost for install.

Some real life examples

If you’re wondering just how much of a seamy-ness tradeoff we’re talking about, then here are two examples. This first picture shows a custom shower install done by a very good tile expert. The wall mosaic is really well done, so you know this installer was good. However, even this pro installer couldn’t get the stone pebble mosaic floor tile seams to completely disappear. You can still see them with a carefull eye:

This second picture shows a custom shower install that I did. The seams between the individual stone pebble mosaic mats are invisible. I took a lot of extra time futzing with the tile sheets and setting a lot of the pebbles individually to puzzle them all together for this completely seamless result:

These are the two extremes you can expect from a skilled natural stone mosaic tile shower floor install. There’s only so much that even a good installer can do with cheap mosaic mats, even with careful dryfitting. But a skilled installer can make seams dissapear with a quality mosaic mat material and some tricks.

Know your material limitations

If you’re wanting to completely eliminate mosaic tile seams in your stone pebble mosaic floor, then talk with your installer first about what specific mosaic tile to choose. If you buy just any random brand/type stone pebble mosaic mats, then you may or may not end up with something that your installer can work with.

At a minimum, understand that installing any brand/type of stone pebble mosaic floor tile will require extra time and attention to detail for your installer. Shower floors aren’t flat. Even very well-engineered and well-manufactured mosaics will therefore require some extra time and care for a seamless result. If this is an important goal, then be sure to communicate this to your installer right at the beginning of your project.

And finally, some tips!

If you’re wanting to use natural stone pebble mosaic for your shower floor and you don’t want any mosaic tile seams, then here are tricks to help get best results.

FIRST, buy twice the tile you actually need. This is where buying from a big box store like HD, Lowes, Floor&Decor, etc can really help. These stores have very generous return policies.

Even well-engineered and well-manufactured stone pebble mosaics will have at least some variation from one sheet to another. Some sheets will fit together perfectly while others simply won’t. So, buy a lot of extras to maximize your chances of getting enough perfect puzzle pieces.

SECOND, plan for a full half-day of careful dry fit layout planning. Mock up the shower floor by test fitting different tile sheets together until you get a near-seamless layout. Then, label each sheet so you can remember where it goes in the overall puzzle.

Since shower floors aren’t flat, it’s best to do this layout planning on the actual shower floor. What fits perfectly on a perfectly flat surface won’t be perfect on a slightly concave sloped surface.

THIRD, don’t use a contrasting grout color. Instead, pick a grout color that matches the majority of the pebbles in your floor mosaic.

Remember that you’re trying to mask the mosaic sheet border seams, not accentuate them. So, use colors to your advantage for this. Feature the tile, not the grout.

FOURTH, make sure your installer is fine with jiggering some individual pebbles at the seams. This takes even more added time, but is the best trick for making seams disappear. If there are one or several mats that simply won’t fit together seamlessly no matter what, then you can peel some of the pebbles off the mesh backing and lay them individually to make a troublesome seam go away.

Again, setting pebbles individually is added time and therefore added expense. So make sure your installer knows to add extra install time to their pricing. A seamless mosaic tile install requires a team effort, and skill, and added time. But this info can hopefully help you get a great result!