Part Three: Waterproofing a Tile Shower

How do you waterproof a tile shower?  There are many methods and ways of doing things, but here is what I chose and got installed it in a weekend. You want to know what it is and how I did it?

This is the kit I ordered. A Schluter-Kerdi shower kit is an all-inclusive installation package containing each of the integrated family of components required to create a maintenance-free, watertight shower assembly without a mortar bed for the tile. 

They offer a lot of different sizes and pieces in a kit so all kits are not created equal.  Spend some time to figure out what you really want the end result to be in your shower.  They make components to install a heated floor in your bathroom, walk-in showers with no curb and long rectangular drains, etc. So many options!

In addition to the kits, they offer the pieces “a la carte” so you don’t have to order the whole kit if you don’t need to.

Before you order the size kit you need, don’t forget to check your local building codes for the required distance between the toilet and the edge of the shower pan/side of the shower.  Yes, there is a required distance. You can find the information online.

Why did I choose this method vs. painting on a waterproofing barrier?  If it wasn’t a full, walk-in shower I might have painted on the waterproof barrier (like if it was a bathtub/shower combo).

I wanted to ensure no water would leak out. The rooms on either side of the bathroom both have cabinets on the walls that back up to the shower and I wanted to be sure that there would be no opportunity for water to leak out. The cabinets would warp, there would be moisture trapped under them and the flooring and I would have to tear apart the shower to fix a leak. Hard pass!

Let me share the way I did my installation and some tips I learned along the way!

When shopping for the correct kit for you, the size refers to the shower pan for the floor of the shower. So pay attention to the size. The pan is made out of a hard styrofoam and is angled for the water to drain.  The foam is able to be tiled over and is completely waterproof.

I bought a 38″ x 60″ because that is the end size of my shower (after checking our local building code).  If you need to customize the shower pan, it is made out of thick styrofoam so you can cut it to whatever size you need.

**Tip** Buy the kit (size of the shower pan) bigger than your dimensions if they don’t offer one the exact sizing you need. Then you can cut it down with any kind of saw – jig saw, hand saw, the multi-tool I used, etc.

Included in the kit I bought is all the items I would need to waterproof all of the areas of the shower: A valve seal to waterproof the opening of the shower turn-on valve, pipe seal to cover the shower head pipe opening, 4 inside corners and 2 outside corners for the shower pan, rolls of membrane (the long strips you put on the walls), drain pipe, drain cover, shower curb and a shower pan.

First place to start (and really important) is to make sure you have the correct mortar for the membrane strips to adhere to the wall. The correct kind is an unmodified thinset mortar. You can use the one directly made by Schluter.

$$ SAVING TIP* – I bought the mortar that you have to mix with water. It is really easy and way less expensive than the premixed one.  Follow the directions on the back of the bag and you can’t mess it up.

You will just want to have this mixer to attach to your drill. It will come in handy later, too, so it is a good investment. I also used it to mix the thinset for the tile installation and I have used it for SO many other projects!

Here is how I installed my Schluter Kerdi Membrane:

1. First I measured out the membrane (large orange rolls in the kit that are thick and waterproof) and cut it to the length I needed the pieces to be. Cutting them before I started was a time/sanity saver.
2. Before you begin with the mortar, be sure to cover your drain! You can use a piece of cardboard, etc or even tape. You don’t want mortar to go in the drain and cause you trouble down the road.I laid a box tape over it nice and tight and then laid a flat piece of large cardboard over that.
3. I used a level to make a straight line on the wall along the outside edge of the shower from the floor to the ceiling where the edge of the shower tile would stop on BOTH sides of the shower. That helped keep my pieces straight and also to not have excess membrane on the outside of the shower space.
4. I mixed the mortar with water and my drill mixer according to directions then I started on the right side, installing the membrane counter-clockwise around the shower.   Using a trowel, I added the mortar to the wall beginning at the level line I drew and smoothed it over the surface the width and height of the first piece of membrane.
5. Then added my first piece of membrane to the mortar.  It is kind of like wallpapering. I pushed out any excess mortar and air to the edges to make the surface nice and smooth with a wide putty knife.  Remember….the tile will be going on top of the membrane so you don’t want any bumps!
6. Once that was installed I moved onto the next piece and overlapped that piece 2″ to 3″ over the edge of the last piece. There are grid lines on the membrane to help keep it straight.   One by one I moved around the shower, installing each piece I had cut.
7. When I got to where the tile would end on the other side of the shower, I measured the the distance from the last piece of membrane to the line (that I made in the beginning with my level), added 3″ for overlap and cut the last piece of membrane down to fit.
8. Then I lined up the last piece of membrane with the level line I drew in the beginning and then overlapped the previous piece I installed.  The ends/outside edges of the membrane are now nice and straight.  For reference, this is where the tile will end.

The niche itself was already waterproofed, so I just had to be sure to get the edges covered. The last thing to complete was to install the shower pan and curb and waterproof that inside and outside of them.

When I installed the shower pan I had to cut it down because once I added the curb the distance between the toilet and the shower was not enough to meet code so I cut the pan down in depth to make sure I could meet code standard.

You can read more about them in the genesis of the build.

For the curb I had to shave a little off the length, but that was no big deal because it is also made of styrofoam and was really easy to cut with my multi-tool. You could also cut it with a hand saw.

I also had to waterproof the shampoo niche I installed. I took 4 smaller strips of the membrane and overlapped them to create a water barrier.  The tile will go over everything in orange. By overlapping all the pieces you ensure a tight bond no water can leak through underneath the tile once it is installed.

You can find all of the techniques and installation videos for the different kind of kits and shower floors on the Schluter website. It is really thorough and really helpful!

In part 1 of this series I covered the plan and prep for the space and in part 2 I covered the choosing a waterproofing method and cutting my shampoo niche.  In part 4 of this series I will share the drain installation.  Yes, it needs its own part, ha!

And there you have it, friends! A waterproofed shower and a shampoo niche all done!  It is messy and I even ended up with mortar on my face, but it is so rewarding when it is completed.

Stay tuned for part four when I share “The Drain”. Oh the drain. I learned a very important $4 trick and so happy I took the time to do it!

Missed the journey so far? See the introduction to this series,  the design vision I had before it even began and what I had to do before I could begin to waterproof the shower.  You will never believe where it all started!