How to Choose the Right Shower Tray Size and Style

The shower tray (also called a shower pan or shower base) is the foundation of your waterproof shower floor. It provides the pre-sloped surface that directs water to the drain — and choosing the wrong size or style means either an expensive return or a compromised installation.

This guide covers everything you need to know to select the right shower tray for your project.

What Is a Shower Tray?

A shower tray is a pre-formed, pre-sloped panel — typically made from EPS (expanded polystyrene) foam — that sits on your subfloor and creates the sloped shower floor surface. The waterproofing membrane bonds on top of it, and tile goes on top of the membrane.

The tray eliminates the need to build a custom mortar bed with hand-sloped mud work. Factory slopes are precise and consistent, which means better drainage and easier tile installation.

Step 1: Measure Your Shower Footprint

Before anything else, get accurate measurements of your shower floor:

  1. Length: Measure the inside dimension from the back wall to the front of the curb (or the shower entry for curbless designs).
  2. Width: Measure the inside dimension from side wall to side wall.
  3. Measure at the subfloor level, not at the top of the backer board. The tray sits on the subfloor, under the backer board and membrane.
  4. Check for square: Measure both diagonals. If they are equal (within 1/4 inch), your shower is square. If not, note which corner is out and by how much — you may need to trim the tray to fit.

Standard shower sizes are 32x32, 36x36, 36x48, 36x60, 32x60, and 48x48 inches. Custom sizes can be achieved by trimming EPS trays with a standard handsaw.

Step 2: Choose Your Drain Type

Your drain type determines which style of tray you need, because the slope direction is built into the tray.

Center Drain (Square/Point Drain) Trays

These trays slope from all four edges toward a center drain opening. The drain cutout is centered (or slightly offset) in the tray.

  • Best for: Standard curbed showers with a square point drain
  • Slope: 1/4 inch per foot from all four sides — creates a subtle pyramid shape
  • Tile consideration: The four-way slope works well with mosaic tile and small-format tiles. Large-format tiles (12 inches and up) may not lay flat due to the compound slope.

Linear Drain Trays

These trays slope in one direction only, from the high side to the low side where the linear drain channel sits.

  • Best for: Modern showers, large-format tile, and curbless designs
  • Slope: 1/4 inch per foot in one direction — a simple flat plane
  • Tile consideration: Any tile size works perfectly on a single-direction slope, including large-format porcelain panels
  • Drain placement: Usually along the back wall, a side wall, or the entry (for curbless showers)

Step 3: Standard vs Curbless

Standard (Curbed) Trays

Standard trays are flat on the bottom and sit directly on the subfloor. The shower curb is built separately on top of the subfloor around the tray perimeter. These are the most common and least expensive option.

Curbless (Barrier-Free) Trays

Curbless trays include a ramped section at the entry edge that transitions from the full tray thickness down to zero. This allows the finished tile surface to be flush with the adjacent bathroom floor — no step or threshold.

  • Require a recessed subfloor to accommodate the tray thickness
  • Linear drain at the entry edge is strongly recommended
  • Essential for ADA-compliant and accessible bathroom designs

Browse all options in the shower trays and pans collection.

Size Chart: Common Shower Dimensions

Here is a reference for standard shower sizes and the typical tray dimensions that fit each:

  • 32 x 32 inches: Compact shower stall — common in half-baths and small master baths. Square drain center tray is standard.
  • 36 x 36 inches: Standard shower stall. Comfortable for one person. Works with center or linear drain.
  • 36 x 48 inches: Common in tub-to-shower conversions. Good balance of size and space efficiency.
  • 36 x 60 inches: Standard tub replacement size. One of the most popular shower sizes. Available in center drain and linear drain configurations.
  • 48 x 48 inches: Square format, popular for corner showers and neo-angle configurations.
  • 32 x 60 inches: Narrower tub replacement. Works well in tight bathrooms where a 36-inch depth is not possible.
  • 48 x 60 inches and larger: Oversized showers, walk-in designs, wet rooms. May require multiple trays or a custom mortar bed approach.

Can You Cut a Shower Tray?

Yes. EPS foam trays can be cut with a standard handsaw, utility knife, or hot wire cutter. If your shower dimensions do not match a standard tray size, buy the next size up and trim to fit. When cutting:

  • Cut from the high side (perimeter), never the drain side
  • Maintain the factory slope by only trimming the edges
  • Ensure the drain opening remains properly positioned after trimming
  • Use a straight edge for clean, accurate cuts

Tray Installation Basics

  1. Dry-fit first: Place the tray in the shower without any adhesive to verify fit, drain alignment, and wall clearances.
  2. Set in thinset: Apply a bed of unmodified thinset to the subfloor using a 1/4 x 1/4 inch square-notch trowel.
  3. Press the tray into the wet thinset and check for level (the tray has its own slope — the top of the tray perimeter edges should be level with each other).
  4. Allow to cure: Let the thinset set for 12-24 hours before applying waterproofing membrane on top of the tray.
  5. Membrane goes on top: The waterproofing membrane covers the tray, seals to the drain flange, and wraps up the walls.

For detailed installation steps, see All About Shower Trays.

Frequently Asked Questions

Do I need a shower tray, or can I use a mortar bed?

You can use either. A mortar bed (hand-mixed and sloped on site) is the traditional approach and allows unlimited custom sizes. However, it requires experience to get the slope right and typically takes 24-48 hours to cure. A pre-sloped tray gives you a factory-accurate slope with no cure wait — you can start waterproofing the same day.

What if my shower is not a standard size?

EPS trays can be trimmed with a handsaw. Buy the next standard size up and cut to fit. For significantly non-standard sizes (L-shaped showers, very large walk-ins), a mortar bed may be the better option, or you can use multiple trays cut and fitted together.

Does the tray replace the waterproofing membrane?

No. The tray provides slope only — it is not waterproof by itself. The waterproofing membrane must be installed on top of the tray, sealed to the drain, and wrapped up the walls. The tray and membrane are two separate layers with different functions.

How much weight can a foam shower tray support?

EPS shower trays have a compressive strength of 15-25 psi, which translates to thousands of pounds per square foot. They easily support the weight of thinset, membrane, tile, and standing occupants. EPS is the same material used in commercial construction for under-slab insulation that supports entire buildings.

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