I received a call the other day from an individual in Canada who wanted some sliced pebble tile for his shower floor and information on how to demo / remove his existing regular style pebble tile. He had installed regular pebble tile two years earlier and loved the look but there were some issues about the installation and the style of pebble that ultimately forced him to the point of removing the tile. His story, which I will share with you, provides some valuable insights into what type of shower floor tiles work well and some important installation tips so that your shower floor provides years of enjoyment.
So let's get back to the call and our conversation. Two years previously, this gentleman bought and installed some regular, natural pebble tile (from an unnamed source) for installation for his shower pan. Unfortunately, there was an issue with the size of some of the pebbles ( general thickness and gauge), the amount of grout between the stones and the slope of the pan. The result was that after each shower there were pockets of residual water that were trapped and could not flow into the drain and caught in small pockets where the grout was uneven ( little divots). Over time, these small little areas of trapped moisture led to red slimy staining. A common source of this goo is a red slime that seems like a red algae but is actually a bacterium, Serratia marcescens which thrives in a moist and humid environment and eats the residue of soap and shampoo. The natural little dams in his shower pan provided an ideal growing environment and a chronic maintenance issue that required constant cleaning and restoration. 2 years of that and he was over it.
Looking back at the installation, he did a great job prepping his shower pan to make it water proof by using Schluter Kerdi, a pliable, sheet-applied, bonded waterproof membrane and vapor retarder. The problem that occurred was that this did not address the slope of his pan, which is super important when using natural pebbles that have a natural randomness to the size, thickness and gauge. One larger pebble with an inconsistent thickness and a slight recession of grout can easily form a small dam and not allow all the water to flow to the drain. A three percent slope from side to center does a great job of minimizing that problem but if that does not exist, well problems can begin to occur. The solution is make sure that you have a real slope to the pan if you plan to use a natural pebble tile.
Now if the slope is correct and you know that the water will have some gravity to help pull it to the drain, the next important thing is to make sure you don't use some low end pebble tile that has a ridiculous amount of random sized pebbles. Not all of these types of tiles are created equal and there are a large amounts of low end Chinese knock offs in the market that have very inconsistent stones and less than ideal quality control. In my opinion, the best of the best are true Balinese mosaics that hand puzzle the pebbles together. This is a very artistic culture and the work of an artisan is very different than a laborer and it really shows. Even the neighboring islands of Java that manufacture pebbles lack the integrity of the original p which have very consistent color, size, thickness and the gauge.
Another consideration that does not have as much reliance on slope ( regardless you have to have some) is going with a sliced pebble tile version where the stones are cut across the top and bottom to form a perfectly flat stone. This more machine manufactured process produces a very uniform shower pan floor and makes any issues with water pooling remote unless there is some sort of installation error.
This brings us back to part of the reason our poor friend in Canada got into the problem he is in. When installing regular, natural pebbles for a shower floor the laying of the tiles requires attention to detail about the stones. If you see a big bulky stone that looks and feel obvious as you run you hand over it, switch it out. I am a big fan of the foot test. A good pebble tile feels comfortable under foot right out of the box. If you do get a awkward spot, it is pretty easy to change it out ( remember these are all hand made so you can handle a few puzzle pieces). I like to lay out the entire pan as it will be installed before I thinset. It allows you to see how the tiles interlock, make sure there are no seems and gives you a nice test ground to make sure the entire floor feels good under foot and does not have any potential areas for the water to pool.
The next really big part of the equation is no matter what the quality of your stones, you have to get the grout nice and even so the water can flow with the slope. This is super easy but does require an extra step that is not typical in most tile jobs. Because the natural stones do have some thickness ( typically 3/8") and are rounded and sloped on the tops and bottoms, there is some massaging of the grout that has to be done in order to get the quality installations you see in many photos.
So as you are applying the grout, in order to get it between all the stones and under the little ledges under each little pebble, you are going to find that you end up burying the pebbles in A LOT of grout. Not to worry all part of the process. The key though is that you have to get rid of that excess grout which is impossible to do when it is all moist. The key is to wait for 15 to 30 minutes after you put it on until the grout begins to set and get dry. Once this begins you can take a nylon scrub brush and gently rub in a circular pattern around all the stones and remove the excess grout. The ideal ratio is 50% of the stone buried ( the grout going right to the transition from the bottom of the pebble to the top) and 50% exposed. If your job is looking like little semi submerged turtles, you need to keep rubbing with the brush. Once the grout starts to cure it gets crumbly so this is not a hard job. But do it too early and you will create divots, holes and worse.
A very common error is the DIY homeowner or the contractor who did not read the pebble tile instructions trying to get rid of all that extra grout with a standard grout sponge. This simply makes the surface of the grout sloppy and difficult to remove. The more sponging the more the harder the grout is to remove. The installations all have the trade mark turtle back look with nice streaks of grout across the top. The other problem is not paying attention to the grout cure time and waiting to long. Given sufficient time and the grout will have become as hard as cement and there is not something you can do to fix that.
Remember the key is taking your time. Make sure you have a good slope and a quality waterproof pan, choose your pebble tiles wisely and take your time installing and the end results will be the magazine and web photos that likely inspired you in the first place.
Have you had a challenging installation or found a trick that makes the job easier? Tell us what you think in the comments so we can all learn a little more.