Kerdi Shower Bathroom Renovation

These clients had a completely unfinished guest bath space that had been sitting unfinished for awhile. Normally, finishing out a full bath takes just a couple weeks max even with a custom walk-in tiled shower. But these folks really wanted a custom tile Kerdi shower bathroom renovation for a lifetime waterproof guarantee. And, the builder had plumbed this upstairs bath for a single vanity sink and a bathtub, not the walk-in shower and double vanity that the homeowners actually wanted.

So, read on for deets on how to craft a truly custom bathroom from scratch!

A kerdi shower waterproofed and ready for tile!

If your bathroom renovation project is dead easy, then you’ll have no problem finding plenty of contractors willing to take it on. But if your project is even a little potentially difficult or out of the ordinary, then finding a reno contractor can be difficult. Fortunately for these folks, custom tile and Kerdi waterproofing are my specialties.

The Kerdi Shower Renovation Challenge?

First off, the wall supply and drain plumbing was originally configured for a single vanity sink. This meant carving into the walls to split the plumbing to accommodate the double-sink vanity that the clients wanted.

Second, the floor drain stubout was configured for a bathtub install. Tthe drain was only 4″ off the wall, which is not ideal for a walk-in shower conversion. And, the toilet was plumbed assuming a bathtub, which wouldn’t work for a full-size shower install. So, that meant carving into the subfloor to rejigger the PVC drains for both the (future) shower and the toilet.

And finally, the lighting was not so great. At all. So, how to solve that with several new dimmable can lights in the ceiling and added vanity lighting on the walls? More carving!

Challenge Accepted!


This is why the space had remained unfinished for so long. The clients couldn’t afford the 40-50% added premium cost of hiring a traditional general contractor, and their efforts to hire individual tradespeople directly (a plumber, a carpenter, an electrician, a tile installer, a painter, etc) wasn’t getting anywhere.

That’s why traditional general contractors come at a premium cost. It can be difficult to even find nearly a half-dozen good specialist subcontractors, nevermind scheduling and coordinating between them. A good general contractor has a big rolodex of contacts. But, that convenience comes with the premium cost.

Their solution? Find a single tradesperson who could do every project step from initial design to final touch-paint brushstroke. This is exactly the conceptual business space that I operate in. And, luckily for the clients, I also operate well in attic crawlspaces!

STEP ZERO: plumbing and carpentry

The crawlspace work was necessary for rejiggering the plumbing to accommodate a split vanity drain, to double the faucet supply plumbing, and to move both the shower and toilet drains. It was also a bit of a tight fit running new wire through the ceiling space to extend the existing circuit for added dimmable can lights.

After redoing the shower drain plumbing, buttoning up the subfloor required additional framing support for the walk-in shower conversion. This is the kind of detail that sometimes get dropped in traditionally-managed renovations with multiple contractors. While bathtubs need extra floor joist support to take the weight of 50+ gallons of water (500+ pounds not counting the added max 300-ish pounds of person(s) in the tub), this support can be safely concentrated at just the two sides of the tub.

A shower, on the other hand, needs almost the same load support but distributed evenly along the entire width of the floor. If you’re converting a second-story bath from a tub to a shower, this is an important design detail.

Subfloor ready with the new supports you can’t see (but that are super-important)!

STEP ONE: make a Kerdi shower base

With the plumbing and floor bracing all set, it was finally time for a straightforward walk-in shower install. Installing a custom-sloped shower base was the first step:

The pics show the process. First, mix drypack “deckmud” (a 5:1 ratio of sand and portland cement). Then, pack the concrete to form a base at least 1″ thick at the drain and with an even continuous 1/8″ per foot slope from the perimeter to the drain.

On a wooden subfloor, it’s also a good idea to line the bottom with plastic sheeting and use wire mesh to add extra strength to the concrete. Finally, it’s also a good idea to cover the concrete with another layer of plastic for drying. Keeping the concrete from drying out too quickly while curing adds extra strength.

STEP TWO: install Kerdi shower waterproofing

The clients chose to use Kerdi waterproofing fabric for the tile substrate, which is a really great choice for a shower that’ll literally last a lifetime (or two). Kerdi also looks pretty cool when installed:

STEP THREE: install the shower tile

Pretty straightforward with the waterproofing in place. The clients chose a stylish oversize subway design with a niche to match the hexagonal marble mosaic shower floor tile.

One cost-saving tip for shower niches? Use natural stone tile for shelving. It’s less expensive than tempered glass and offers lots of design flexibility:

STEP FOUR: install the floor tile

Most of the work for this Kerdi shower bathroom renovation went to making the shower. But the rest of the bathroom also needed tile, paint, trim, and fixtures.

Solid surface ready for tile

This bathroom floor tile install required an added step for leveling. Since the subfloor was a bit out of plumb, pouring a layer of “LevelQuik” self-leveling concrete mix made for a much easier tile install. Since the clients chose large format 12″x24″ ceramic tile for the bathroom floor, I wanted to ensure that they wouldn’t have any problems with tile or grout cracking in the future.

In addition to making a dead-level substrate surface, the LevelQuick layer also adds a bit of crack prevention by decoupling the tile from the subfloor. That way, even a slightly bouncy subfloor won’t translate into cracked floor tile.

With a dead-level solid substrate, tile install was simply a matter of carefully planning the pattern and then laying ’em down. Easy peasy!

STEP FIVE: install the finish bits!

Need a double vanity with marble top installed with fixture and drain plumbing (and a toilet)? No problem. Need some light electrical for installing new wall and ceiling lighting on an existing circuit? Also not a problem. And baseboard with trim paint? No problem at all!

With the tile and grouting done, the finish bits took just a few extra days. The rest of the bathroom reno was done even before the glass folks were scheduled for the shower partition install.

The clients chose some really stylish materials, had a great eye for matching elements, and happily were very happy with the install results. My ancient iPhone snapshots don’t do the finished look justice:

And, a big fisheye lens final view of this Kerdi shower bathroom renovation: