Fixing the WORST, part deux!

This post describes the process of fixing perhaps the worst shower install imaginable. If you’d like the gory background for this project, then check out this previous post. If you’d instead just like to see how to apply a very creative (but still fully guaranteed) fix for a bizarre leaky shower problem, then read on!

The Problem (abbreviated version)

A previous renovation contractor had installed a ‘custom’ tile shower with a fiberglass waterproofing pan underneath a leaky synthetic cultured marble shower floor base. This happened before the current owners bought the house. About 24 months after buying the house, the shower started overflowing water into the flooring and the homeowners figured out there was a problem after noticing water dripping from the laundry room ceiling below. Being handy DIY folks, the homeowners then carved into the first floor ceiling and saw water dripping from the plywood subfloor underneath the second-floor master bathroom shower.

A ‘custom’ tile shower with failed (or even nonexistent) waterproofing is actually a pretty common problem. So common that I could probably make an entire career out of fixing improper tile shower construction.

This one, though, was uniquely improper. Demolishing everything to the plywood subfloor revealed easy to work with PVC drain piping and no mold in the wall or floor framing. But, not replacing the entire shower required working with a completely ridiculous shower design that used synthetic cultured marble slabs for a tile wall substrate with glued-on large format 2×2-ft travertine tiles.

The (main) Challenge

Fixing a leaky shower by replacing the entire base with a properly installed drain, a properly sloped concrete base, and a guaranteed waterproof layer of Kerdi fabric underneath the shower floor tiles and RedGard underneath the first ~6-in of wall tiles is usually a straightforward fix for these situations. Usually though, the previous bathroom reno contractor would at least have used concrete backerboard as a shower wall substrate.

In this case, the previous contractor had (bizarrely) used slabs of synthetic cultured marble for the shower wall substrate. Conventional tiling materials won’t adhere to synthetic marble. So, that made how to fix the leaky shower problem without demolishing the entire shower a bit of a magic trick puzzler.

The (minor) Challenge

This shower also had a frameless glass door that the homeowners really definitely did not want to pay ~$900 to replace. Custom frameless glass doors and dividers are truly custom cut to +/- 1/8″ tolerances. So, if you’re trying to completely re-build a shower base, then you’ve got to make sure that the shower doorway opening doesn’t change dimensions at all if you’re going to have a hope of re-using a previously installed custom cut frameless glass door.

In other words, the plumber and carpenter and tile installer (ie — me) needs to be super-precise to have a hope of being able to reinstall and re-use the frameless glass door. I luckily have a good bit of previous experience doing just that, but it was nevertheless an added challenge.

The Plan

Quite straightforward, with just one wrinkle:

  1. Remove the first course of 2×2-ft travertine limestone wall tile (including the tile on the shower bench)
  2. Demo the shower doorway threshhold and the shower base down to the plywood subfloor
  3. Install new drain plumbing and a properly sloped concrete base
  4. Install KERDI waterproofing for the shower floor and waterproof “Silka” brand masonry caulk and RedGard waterproofing for the base of the shower walls and bench
  5. Re-tile the shower floor and walls, grout, and re-install the glass shower door

The wrinkle was how to work with the synthetic cultured marble wall substrate to re-install tile without having to use something completely ridiculous like Liquid Nails adhesive (as the previous contractor had done). Read on for the fix description!

The Plumbing and Waterproofing

The demo step is already described in detail in the previous Fixing the Worst, part Uno! post. Once the shower base was taken out to the subfloor framing, re-plumbing and building everything back up was very straightforward.

That’s the convenient thing about working on second-floor shower fixes — there is generally lots of room to work once you carve out a piece of the subfloor. And, repairing everything just takes a little bit of very basic carpentry.

Once the Kerdi drain was in place and the shower curb was reframed, packing in the concrete base looked like this:

And, the waterproofing install looked like this:

Using Kerdi fabric to waterproof the shower floor was a no-brainer. Kerdi is great for waterproofing, since it’s a modern waterproof hydrophobic barrier that bonds with thinset (so that tile can be installed directly on top of it). Making a continuous waterproofing barrier that would run up the synthetic cultured marble wall substrate? Not so straightforward.

Not many waterproofing materials will bond to synthetic marble. There is one, however, that could do the trick. It’s a masonry caulk that’s sold by Kerdi under the brand name “Kerdi-Fix“. However, at nearly $30 a tube, that’s some expensive caulk. Luckily, there’s a generic equivalent. This “Sikaflex construction sealant” is the same formulation (polyurethane, waterproof, bonds to masonry and thinset, etc) at a fraction of the Kerdi brand-name price.

Once the weird synthetic marble wall substrate surfaces were slathered with Silkaflex, another layer of RedGard paint-on elastomeric waterproofing was the last prep step before tiling.

The Tile re-Install

The shower walls got replacement large-format travertine tiles to match the previous tile install. For the floor, however, then clients chose to go with a very nice variegated natural stone mosaic tile to add more visual interest. Additionally, they chose to wrap the floor tile up the front of the shower bench to make the space seem visually larger than it actually was.

This was a neat trick to make the space appear larger while also brightening it up quite a bit.

The Finish!

With grouting and shower door re-install (which went back in with a better fit than before), the project was done:

A now waterproof shower with more attractive tile — way less expensive than a complete shower replacement, and still guaranteed for decades. Yay creative fixes!