Complete Guide to Installing Schluter Kerdi Waterproofing System

Isaac Ostrom
3 days ago
9 min read

Schluter Kerdi is one of the most popular waterproofing systems for tiled showers, and I get why. When it’s done right, it’s clean, it’s straightforward, and it’s a legit bonded waterproof system that lets you build a shower that performs.

In this tutorial, I’m walking you through installing a Schluter Kerdi shower kit from start to finish: foam pan, curb, wall membrane, banding, corners, niche, and a triangular corner bench. I’m also using Schluter All-Set for the first time in this video, so I’ll tell you exactly what I liked, what I paid attention to, and where guys typically mess this up.

If you’re a homeowner, this is going to help you understand what “good waterproofing” actually looks like before the tile ever goes on. If you’re a setter, I’m going to hit the real-world stuff: trowel selection, open time, coverage checks, buildup management at overlaps, and how I like to handle benches so they don’t become a future failure point.

Key Takeaways for Homeowners & Pros [TLDR Version]

The kit is great, but you still have to install it like a pro. The system is only as good as your overlaps, coverage, and detailing.
Schluter All-Set has a specific mixing rhythm. Don’t wing it: mix 5 minutes, slack 10, remix 3. That’s your “18-minute mud” reality.
Pre-wet your walls before membrane. It cleans dust and buys you open time so your mortar doesn’t skin over on you.
Comb your mortar in one direction (I like horizontal on walls) so you can push air out easier when embedding the fleece.
Do a pull test. You’re not guessing—you’re verifying coverage. I want to see full transfer behind the membrane.
Foam pans are fragile in shipping. If it shows up damaged, get it replaced. (It happens.)
Don’t create a triple-overlap mountain at your corners—plan your corner/band sequence and trim where needed.
Benches are a big failure point. Treat them like they’re going to get hammered with water—because they are.

Tools Required (What I Actually Used)

Here’s what shows up in this install:

Mixing drill + paddle (for All-Set)
Buckets, measuring water, sponge
Kerdi trowel (1/8" x 1/8" square notch) and/or 3/16" V-notch for membrane (either works—I used the Kerdi trowel here)
1/4" x 3/8" notch trowel (for setting the foam tray)
Margin trowel
6" taping knife (I like having two knives when embedding corners/band)
Utility knife/razor knife (for trimming membrane, foam, and corner pieces)
Tape measure, level, and a plumb reference
Kerdi-Fix (for specific bonding/detailing situations)

What’s In the Schluter Kerdi Shower Kit (And What You Still Have to Buy)

The kit I’m installing includes the big ticket items: a pre-formed foam shower pan, a pre-formed curb, Kerdi membrane for the walls, and the corners/band you need to make your seams waterproof. In this case, the triangular corner bench and the niche were purchased separately.

That’s pretty normal. Guys assume the kit is “everything,” then they’re frustrated mid-job when they realize the niche and bench aren’t in the box. So just know that going in.

Step 1: Prep Work That Makes the Waterproofing Easy

Before I even think about spreading mortar, I want my substrate ready. In this shower, we had green board up, insulation behind an exterior wall, and we had to make a decision on niche placement.

Here’s the real-life jobsite thing: sometimes your studs don’t cooperate. We couldn’t move the studs because there was a kitchen on the other side, so the niche ended up offset. Instead of leaving it looking like we “missed center,” I skewed it all the way to the side so it looks intentional. That’s not a Schluter tip—that’s a “don’t make it look like an accident” tip.

For fastening, we didn’t have washers (I probably should’ve used them), but we did use a white head screw, and I ran a solid bead of Kerdi-Fix on the stud so that niche is glued in there like it owes me money. It’s not coming out.

Then I’m thinking ahead: where am I stopping waterproofing? We had a 38" pan and a curb that put us at about 42 1/2" for the waterproofing height reference, so I know where to comb thinset up the wall and keep things clean.

Step 2: Mixing Schluter All-Set (The “18-Minute Mud” Reality)

This was my first time using Schluter All-Set, and the mixing sequence matters.

Here’s the rhythm:

Mix for 5 minutes
Let it slack for 10 minutes
Remix for 3 minutes

That’s the deal. If you send your apprentice to “go mix mud” and it takes 18 minutes, now you know why.

And I’ll say this: I like that Schluter has specific consistencies for different steps. Membrane mortar wants to be a bit looser than “setting tile” mortar. Keep that straight so you’re not fighting the material.

Step 3: Pre-Wet the Walls (This Is One of Those Small Big Deals)

Before I spread mortar, I pre-wet the walls.

Why?

It cleans dust off the surface (dust is a bond breaker)
It helps with open time so your thinset doesn’t skin over too fast

Open time is basically the clock you’re racing: the time between spreading mortar and when it glazes over and becomes useless for bonding. Pre-wetting buys you time, especially in hot conditions.

Step 4: Troweling Thinset Correctly for Kerdi Membrane

I “key in” the thinset with the flat side of my trowel first—get it married to the wall—then I comb it out.

And when I comb, I want consistent trowel direction. If you change direction, you trap air. I’d rather comb horizontal on the wall because it makes it easier to push air out when embedding the sheet.

This is also where All-Set impressed me. Modified thinsets generally give you better open time, and I’m a fan of that. When you’re working and it’s hot, that matters.

Step 5: Hanging the Kerdi Membrane Without Wrinkles and Without Guessing

When I hang membrane, I like a plumb reference. I start clean and straight so I’m not fighting wrinkles the whole way down the wall.

Then embed it properly. Not gently like you’re petting a cat—firm enough to get the fleece locked into the mortar.

And at some point, do a pull test. Schluter recommends it, and I’m a believer because it removes the guesswork. Peel a corner back and look at the coverage. I want to see good transfer—clean, even coverage—so I know the fleece actually bonded.

If you don’t test, you’re basically just hoping.

Once the sheets are up, then we band and corner the seams.

Step 6: Foam Pan Install (And Why Shipping Damage Is a Real Thing)

Next up is the foam pan. This was my first foam pan in a while, and it was my first time using one that already had the membrane laminated on it. (Older style: just white foam and you’d wrap it yourself.)

The first pan that showed up in the kit was damaged in shipping. Foam is fragile, and UPS is… UPS. Schluter stepped up and shipped a replacement without a bunch of drama, which I respect.

We had to cut the pan to fit, and then to set the tray, Schluter calls for a 1/4" x 3/8" notch trowel. That’s exactly what I used.

Quick note on the factory tape

There’s tape on the pan assembly. My assumption here is: don’t mess with it. It’s there to reinforce and hold things stable. In the instructions, it literally says “do not remove,” so… don’t remove it.

Drain transition: don’t get sloppy here

This is one of the most important waterproofing transitions in the whole shower. I’m careful not to tear the membrane, and I’m using my fingers to pack mortar where I need it so I’m not damaging anything. Then I’m checking coverage.

When the pan is set, you’re in a good spot. The next day, you can finish banding and start thinking tile.

Step 7: Bench Installation (I Did It “Backwards” on Purpose)

Now we’re back and installing the triangular corner bench.

The instructions show bench first, then pan cut to it. We did it backwards—pan first, bench second.

The only issue with doing it this way is the pan already has slope. The bottom of the bench is hollow, so if you set it straight onto a sloped surface, you can create gaps where you don’t want them. So I cut the bottom and built a slope into it so it sits tight where it needs to.

Also, the instructions show thinset on the entire back and floor. To me, that feels pointless because the bench is only contacting at the support points anyway. So I used Kerdi-Fix where I wanted strong structural bond, and thinset where I needed fill/build-up. Kerdi-Fix is great for bonding, but it’s not your “build up an eighth inch” product—that’s where thinset comes in.

Then I leveled the face and checked everything. One thing I like about Kerdi-Fix: it kind of “sucks” things in and holds them without sagging like thinset can. Once it’s in, it’s stuck.

Step 8: Banding and Corners Around the Pan and Bench (Avoid the Buildup Monster)

After the bench is in, we band the floor-to-wall connection and start detailing the bench corners.

This is where a lot of showers get sloppy. Guys don’t think ahead, and they accidentally build a triple-layer overlap right where tile needs to sit flat. That can cause lippage issues, weird tile cuts, and just a nasty-looking install.

The bench comes with special corners labeled right and left—unique folds you can’t really replicate cleanly with generic corners. I like installing corners first (with one exception: these bench corners are a little different because I’m specifically trying to avoid that triple overlap).

The corners have a “leg” that basically tells you where your band should stop so you maintain overlap without stacking layers like a wedding cake. That’s good system design.

My embedding tools here

I’m usually using a margin trowel and a 6" taping knife. Honestly, I like having two knives so one can hold the corner in place while the other embeds the fleece into the thinset. You want mechanical bond—don’t just smear it and walk away.

And here’s the technique:

First pass: light pressure, just get it positioned
Next passes: more pressure, really embed it

If something needs trimming to reduce buildup, trim it. That’s not “breaking the system.” That’s installing it intelligently.

Step 9: Why I Treat Benches Like a High-Risk Area

Benches get hammered with water. It’s not theoretical. Water runs down the wall, hits the bench, sits on edges, and finds the weak spots.

A lot of failures happen where water sits—especially along back lines and corners—because people underestimate how much water ends up there. That’s why I’m picky about bench waterproofing.

Do it once. Do it right. And don’t treat the bench like an accessory—it’s part of the waterproof envelope.

What’s Next

Once all your membrane, band, and corners are in, you’re basically ready for tile. In the video, I wrap it up and point you to more Kerdi install videos because this topic has a lot of nuance and it helps to see multiple installs.

If you want to keep learning this stuff (and you want feedback from other setters), check out the Tile Coach Forum. That’s where these “what would you do here?” questions get answered fast.

FAQs

1) What comes in a Schluter Kerdi shower kit?

Typically: foam pan, curb, Kerdi membrane, band, and corners. In this install, the triangular corner bench and niche were purchased separately.

2) Do I really need to pre-wet the walls before installing Kerdi?

Yes. It helps remove dust and gives you more open time so your thinset doesn’t skin over while you’re working.

3) What’s the correct mixing process for Schluter All-Set?

Mix 5 minutes, let it slack 10 minutes, then remix 3 minutes. Plan for that time—don’t rush it.

4) What trowel should I use for the Kerdi membrane?

A Kerdi trowel (1/8" x 1/8" square notch) works great, and a 3/16" V-notch is another common option.

5) What trowel should I use for setting the foam pan?

Schluter calls for a 1/4" x 3/8" notch trowel for the shower tray install.

6) Should I remove tape that comes on the foam pan?

No. If the instructions say “do not remove,” don’t remove it. It’s there for reinforcement/stability.

7) Why do a pull test on Kerdi membrane?

Because it proves you’re getting proper coverage and fleece transfer instead of guessing. If coverage is weak, fix it now—before tile hides it.

8) What’s the biggest mistake people make around corners and seams?

Creating too much buildup by stacking overlaps without a plan. Do corners strategically so you don’t end up with triple-layer lumps where tile needs to sit flat.

9) Why are shower benches a common failure point?

Because they see heavy water exposure and water can sit at edges/corners if the waterproofing details are sloppy. Treat the bench like a high-risk area.

10) What should I do if my foam pan arrives damaged?

Get it replaced. Foam is fragile in shipping, and it’s not worth trying to “make it work” with a compromised tray.

Final Thoughts

I’ll end it the same way I approach most things in tile: the system matters, but the installer matters more. Kerdi can be an awesome shower system—clean, efficient, and solid—but only if you’re serious about coverage, overlaps, and the details around transitions.

If you’re learning this, don’t just watch one video and call it good. This stuff has nuance, and seeing different installs helps it click. In the video I mention I’ve got a whole playlist of Kerdi installs going back years, and it’s worth digging through if you want to get confident.

And if you want to be around other people who actually care about doing it right, hop into the Tile Coach Forum. That’s where the real-world questions get answered.