How to Extend ANY Schluter Shower Tray

Schluter shower tray installation is very easy. In fact, I enjoy the process a lot.

But sometimes customization is needed. For example, when the existing shower is bigger than the Schluter tray sizes available.

In this tutorial, you’ll learn how to extend any Schluter shower tray using dry pack.

Let’s dive in.

Why Use the Schluter KERDI Shower Tray

I get this question a lot.

The primary reason any DIYer or professional should use a Schluter KERDI shower tray is that it works.

First, prefab shower trays are sloped properly. This means water will drain from the four corners to the shower drain.

Second, Schluter Systems shower tray options come in different sizes.

This makes choosing the right one fairly simple.

Third, waterproofing the tray is easy because a waterproof fleece is already on the surface.

That said, many homeowners make several KERDI shower pan mistakes when waterproofing the transition to the walls, curb, and bench.

Finally, the Schluter shower drain is, in my opinion, the best because it’s solvent-welded and provides ease of use when setting the shower tray tile.

But on top of all this, every Schluter shower tray can be cut down or extended…As I mentioned earlier.

Best Method for Extending Schluter KERDI Shower Tray

Extending or enlarging the Schluter Systems shower tray is done with dry pack mortar.

What is a dry pack mortar?

It’s Portland cement and sand. One great pre-made option is Mapei 4-to-1 Mud Bed Mix, this can be found at most Lowe’s or tile supply shops.

Does Schluter approve this method?

Yes, the Schluter Handbook shows this method when installing Schluter shower trays.

But here’s one annoying caveat:

Cure time.

Dry pack mortars require curing before any waterproofing can begin.

For example, Mapei recommends letting their Mud Bed Mix cure for at least 24 hours to allow water to evaporate.

If you skip this step, you might sabotage your shower remodeling project.

Step-by-Step for Extending Schluter Shower Trays

While it’s easy to make any KERDI shower tray bigger, there are specific steps.

So here’s the step-by-step guide:

Step 1 is to apply modified thin-set to the substrate, e.g., plywood or concrete.

I use the Schluter Multi-Use trowel for this and apply Schluter ALL-SET to the floor, side of the tray, and walls.

Step 2 is pouring Mapei 4-to-1 Mud Bed Mix onto the thin-set

I mix the Mud Bed Mix using about 2 quarts per 55-pound bag. But I also use this water ratio to mix up small portions; it’s not necessary to mix an entire bag on most projects.

Step 3 is to pack the Mud Bed Mix with a wood float.

Step 4 is to screed the Mud Bed Mix to accommodate 1/4-inch of slope per linear foot.

For example, if you need to extend the shower tray by 12 inches and the tray is 1 inch thick, that means the Mud Bed Mix should be 1-1/4 inches thick at the wall.

I mark the desired height on the wall and pack the Mud Bud Mix to it.

But in this situation, I’m screeding the Mud Bed Mix to my DITRA-HEAT mat for the Schluter curbless shower.

Step 5 is to smooth the Mud Bed Mix with a steel finishing trowel.

I use circular motions to create a smooth surface.

And that’s pretty much it for extending any Schluter shower tray.

That said, you need to let the Mud Bed Mix cure and waterproof it. I like to let the shower tray extension cure for 48 hours and then use KERDI or KERDI-BAND to waterproof it.

Installing the shower tray is just one part of bathroom renovations.

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Jeff