A Shower Floor Re-tile

Textured pebble mosic tile is one of those shower floor choices that you either love or hate. Some folks really like the feeling of a hard reflexology foot massage while showering. Most folks, however, really don’t appreciate having to start every morning by being forced to stand on hard pebbles. The couple who bought a house with this shower floor were not fans of the “feature.”

That’s some pretty rough texture!

In addition to being painful for tender feet, this pebble mosaic also wasn’t expertly laid out. A keen OCD eye will definitely spot the seams (which could have been eliminated with some advance planning). The whole shower floor also wasn’t completely evenly sloped to the drain. An aggressive 1/4-in per foot pitch is particularly crucial for highly textured pebble mosaic surfaces like this, since any slow to drain dead spots will really encourage surface bacterial growth. And finally, the original installer apparently struggled to make clean cuts in the mosaic pebble mats and “finished” with a terrible grouting job.

So this shower floor was painful to stand on, ugly to look at, and unsanitary to boot. Very disappointing for the new homeowners who didn’t want to spend each day showering in sandals with their eyes closed.

The Challenge

Sometimes it’s possible to remove and replace shower floor tile if you know beforehand exactly what kind of waterproofing was used below the surface. Unfortunately the new homeowners didn’t know what kind of waterproofing had been used for this shower.

Since there were no signs of any shower leakage, carving into the tile floor would have been very risky. There are several different ways to properly waterproof a shower, and some of those methods involve putting the waterproofing layer quite close to the tile floor surface. And accidentally puncturing the waterproofing layer of an otherwise watertight shower floor is like cracking your car’s engine block. The next step after that is completely replacing the entire shower.

The most conservative “do no harm” approach for re-doing the floor of an otherwise watertight shower is therefore to simply re-tile right over top of the existing floor tile. Traditional shower construction already has a ~2-in concrete mortar layer between the waterproofing and surface tile layers. So, just adding a bit more mortar and tile on top of the previous layer doesn’t increase the overall shower pan thickness by much. This approach also doesn’t risk damaging the waterproofing.

A proper waterproofing liner is installed BELOW the shower floor tile!

Remember that tile and grout are not waterproof. Therefore, tiling on top of an existing tile layer won’t create a moisture sandwich. Instead, it’s the most conservative approach to fixing a badly tiled shower floor without compromising an otherwise well done watertight shower install.

So the primary challenge on this project was to smooth and reslope the existing rough pebbled surface with the least amount of added thinset possible, and to re-tile with a new shower floor that the homeowners would love. Did it work? Read on to find out!

The Plan

The homeowners were enthusiastic to try fixing their painful and unsanitary shower floor without having to rip out everything for a complete redo. This was possible with just three steps:

  1. Reslope the existing pebbled surface using precisely mixed thinset
  2. Retile with a nice retro art deco mosaic pattern
  3. Raise the drain grate and regrout the shower floor and perimeter

The rest of the master bath was done in a midcentury -style classic black and white decor, so the homeowners wanted their new shower floor to fit this same general aesthetic.

One of these design elements was NOT like the others!

The hexagonal mosaic floor tile they settled on was a great choice. Not only a matte finish for anti-slip, but also just 1/8-in thick for minimal height gain.

The nice thing about classic tile is it’s generally both inexpensive and easy to source. Easy sourcing is especially critical nowadays in the midst of an ongoing multiyear pandemic.

STEP ONE: Reslope the pebbled surface

This first step was the trickiest, and probably not something that you’d want to attempt without some previous practice. Sloping a shower floor from scratch is already a finicky process even utilizing easy to work with drypack deck mud. Using a skimcoat layer of thinset to achieve the same finish takes finesse. But if you do want to give it a go yourself (or just want to make sure that your contractor is working smartly), then here are some tips.

FIRST, use a quality modified thinset mix. You want the reslope layer to be thin as possible, and modified thinset is less grainy and therefore easier to smooth out than basic unmodified thinset. You’ll also need to use less water than normal for your reslope mix, since you will need the thinset to be thick enough to actually hold a slope. The polymer additives in modified thinset will allow you to make a stiff mix that will still set up and cure to a firm finish.

SECOND, use masking tape around the floor perimeter for a guide. The whole point of redoing a shower floor is to make the new floor perfectly sloped. So do some preplanning to make the job easier, especially for getting the corners just right! Also, don’t be like this previous installer who didn’t even bother to trim away mosaic mat nylon strings before grouting. What a dope.

THIRD, use a wide blade drywall knife for spreading and working your stiff thinset mix. You’re basically doing a skimcoat, just like smoothing a plaster wall. So, use your plastering skills and tools. Work in sections and take your time.

FINALLY, don’t try to do all the resloping in one day. Even a stiff thinset mix will slump a bit and also contract some when cured. It’s also a lot harder to slope than drypack concrete in the first place, so don’t try for perfection on the first day.

Instead, just get the first application good ’nuff for an effective start. Then you can let it dry and cure overnight and make it perfect the next day. Simply use a bubble level to identify any high spots and shave those down using a 4-in drywall knife as a scraper. Then identify and mark any low spots, and fill those in with a bit more thinset.

STEP TWO: Retile

A mosaic tile pattern is sometimes easy to lay out and install without any thought. This was not one of those times.

The homeowners wanted their new shower floor to match the same art deco theme as the adjacent bathroom floor. They also wanted some custom design flair. Challenge accepted!

STEP THREE: Regrout and raise the drain grate!

The grouting step was a little finicky as well. The homeowners chose a light grey grout color to both make the white hex mosaic tile pop and also make the whole shower easier to keep clean looking. The problem with grey grout is that it’s actually one of the most difficult grout shades to install with a completely uniform final shade. Grout mix will dry in the bucket over time, and many grey grout mixes in particular are very sensitive to varying moisture levels while curing. This is why you want to grout a mosaic surface quickly and also pick the most forgiving grout mix possible for best results.

Raising the drain grate was easy. The original shower installers had used the simplest builder grade round screw-in two piece shower drain assembly available. Because these cheap drains are so common (and so commonly installed to an improper depth), there are lots of shim kits available for raising a round drain grate. Easy peasy.

The Finish!

Here’s what the final result looked like. Instead of a painful, sloppy, slow draining pebble mess the homeowners now have a smooth and perfectly sloped art deco -style shower floor.

Now THAT’S an improvement!

Remember that the waterproofing layer in a correctly engineered tile shower install is below the floor tile. So while a double-thick tile layer may seem like it’d cause the shower floor to absorb more moisture in the tile and deck mud layers than before, correcting a badly sloped floor will actually in practice reduce the amount of water that’s absorbed by the deck mud layer during showers. Think about it. The more quickly water goes down the drain, the less water is absorbed by the floor.

This particular shower floor fix was actually done two years ago, way back in September 2019. I checked back with the homeowners just last week to see how it’s held up. They said that their shower was still performing beautifully. Re-tiling the floor made their shower not only easy on the feet but also much quicker to dry between uses and easier to clean than before. They’re still super happy with the results even years later.

Yay success!