The Mosaic Tile Seam-y Side

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NOT my work — just a typical example!

A popular choice for many of the custom shower renovations that I’ve done is ‘natural’ stone pebble mosaic. These aren’t actually made from completely natural stones, but rather sandstone or other sedimentary rocks that have been machine cut, honed, and fit into 12×12 -in mosaic mats designed to fit together like an easy jiggsaw puzzle where every puzzle piece (ideally) fits seamlessly with any other piece:

Upsides to using pebble mosaic for a shower floor

First, the mosaic patterns usually leave lots of area for grout, which makes for a nice slip-resistant floor surface.

Second, there are lots of different stone types and colors/shades to choose from, which makes it easy to match with just about any wall or trim tile.

And third, it seems to be quite a popular design trend based on the number of local installs that I’ve done here in Austin, TX, the past few years:

Downsides to pebble mosaic shower floors

First, pebble mosaics can be pricey since $20-ft2 is a good guesstimate for even the least expensive mosaic mats that will fit together at least reasonably well.

Second, any natural stone tile will need to be treated with a good penetrating sealer before grouting to prevent a permanent grout haze from sticking to the stone’s surface and/or causing discoloration. This adds an extra install step and therefore a bit of added labor expense.

Third and most important to think about beforehand, specific brands and styles of stone pebble mosaic mats can be difficult or sometimes even impossible to install with a completely seamless finish.

Seriously, consider your tolerance for seamy-ness!

Some stone pebble mosaic mats are engineered so that any side of a mat can (ideally) match up seamlessly with any side of any other mat. This gives some flexibility for matching mats together to minimize the appearance of seams. If each mat can be rotated 90, 180, or 270 degrees, then you have lots of options for (ideally) seamless matching.

Less expensive stone pebble mosaic mats are often designed and manufactured so that only two sides of a mat can match with the layout pattern of an adjacent mat. This cuts down on manufacturing costs but also really limits the installer’s options for getting a truly seamless result.

In general, 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. However, if you’ve got some OCD tendencies or are wanting to use a really contrasting grout color for your shower floor, then budget ~$30-ft2 as the minimum for your stone mosaic floor tile cost and also expect a higher labor cost for install.

Here are some examples

If you’re wondering just how much of a seamy-ness tradeoff we’re talking about, then here are a few example pics.

This first picture shows a custom shower install done by a very good tile expert. You know this installer was good because the wall mosiac is so well done. However, even this pro  installer couldn’t get the stone pebble mosaic floor tile seams to completely disappear:

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Even a pro installer can’t overcome EVERY material limitation

This second picture shows a custom shower install that I did. The seams between the stone pebble mosaic mats are pretty much invisible, but it 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 near-seamless result:

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Used EVERY trick for this install!

The bottom line? Know your material limitations.

If you’re wanting a completely seamless stone pebble mosaic floor for your custom shower, then be sure to talk with your installer first about what specific mosaic tile to choose. If you charge ahead and buy some 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, which means that even very well-engineered and well-manufactured mosaics will require some extra time and care for a seamless or at least close to 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 want a completely seamless result, then here are a few tricks of the trade for maximizing the chances for perfection.

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 since these stores have very generous return policies.

Even well-engineered and well-manufactured stone pebble mosaics will have 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 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 probably 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.

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Feature the stones, not the grout!

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

FOURTH, make sure your installer is fine with jiggering some 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, but if a completely seamless install is your priority then make sure your installer knows to add extra install time to their pricing!