Support Center / Showers, Panels & Accessories / How Do I Measure My Space for a Shower Pan or Base?
Back to Showers, Panels & Accessories

How Do I Measure My Space for a Shower Pan or Base?

Updated September 2026

▶Glossary7
  1. Why the Measurements Have to Be Exact
  2. Measuring the Opening
  3. Locating the Drain
  4. Sizes to Compare Against and the Final Check
  5. Related Guides
  6. Related Videos
  7. Common Questions

Measure three things: the alcove where the base will sit, taken both between the studs and at the finished walls, the height of the space if wall panels will go above the base, and the location of the existing drain measured from the center of the pipe to the framing behind it and to the nearer side wall. Compare those figures with the Specification drawing for the base you want, because an Ella base cannot be trimmed on site and its drain position is molded in. The framing side of the job is covered in Ella Shower Rough Opening, Standing Area and Floor Width: What to Measure Before You Frame.

Why the Measurements Have to Be Exact

An Ella acrylic shower base is vacuum-molded from an acrylic-capped ABS sheet with high-density foam bonded underneath, and the slope, threshold and drain opening are all molded into that shell. Cutting into it on site is not possible, so the base has to be ordered in the exact size and drain position you need. Standard sizes such as 60 by 30 and 60 by 33 inches are stocked, other sizes are made to order, and if a wall or a filler piece is needed to close a gap, it is planned at the time of the order. How the shell is built and set is explained in What the Ella Acrylic Shower Base Is Made Of and How It Is Installed.

Measuring the Opening

  • Measure the alcove width between the studs and its depth from the back studs to the front edge. The base sits against the framing once finish materials are removed, so measure to the studs where possible.
  • Measure the finished opening with your contractor as well, so you both know how much tile or surround the base will displace.
  • Measure the width, length and height of the existing tub or shower alcove, since the wall panels above the base need the height figure.
  • Check the pocket for square, plumb and level, because the stall fastens to the studs. If the alcove is wider than the unit, the extra space is furred out before installation.
  • Download the Specification drawing for your exact model, or ask your Ella dealer or the team at (800) 480-6850 for the current PDF, and frame to the drawing.

Locating the Drain

The Specification drawing shows the outside dimensions of the base, the threshold, and the drain center measured from the back wall and the side wall. Have your plumber measure from the center of the existing drain pipe to the wall framing behind it and to the framing on the nearer side wall, then compare the two figures with the drawing. The numbers change with every model and drain position: one right-drain base lists the drain center 15 1/2 inches from the back wall and 9 1/2 inches from the front, while one center-drain base places it 19 inches from the back wall and 24 inches from the side wall. Always say which drain position you are ordering, because left, right and center are different numbers and the position cannot be moved to the other side afterward. If the figures match within the tolerance your plumber is comfortable with, the base can be set over the existing line. If not, a licensed plumber can relocate the line, or you can request a custom-size base with the drain placed to your measurements, such as a 36 by 36 inch corner base with the drain 9 5/8 inches from each of two adjacent walls. Because the online drain-placement tool can round measurements up to the nearest inch, confirm your exact drain location with the team at (800) 480-6850 before the base is built. Reading the drawing is walked through in Shower Drain Rough-In: How Far the Drain Sits From the Back Wall and Side Wall.

Sizes to Compare Against and the Final Check

Stock bases include 60 by 30 and 60 by 33 inches. Barrier-free, roll-in bases with a low threshold are available in a 32 by 60 inch size, and a 3-inch step-in threshold base is offered for those who prefer a slightly raised edge. Custom sizes are built to the dimensions and drain position you supply. The range is compared in Walk-In Tub and Shower Base Sizes and How to Measure for Fit. Once the base arrives, treat the drawing as the starting point and the dry fit as the final word: set the base in the pocket, mark the drain center through the base opening, and only then cut and set the drain pipe. The base goes directly on a flat subfloor or a concrete floor, with dips corrected using self-leveling compound rather than a mud bed.

Chapters in this video
  1. 0:00 Receiving and Inspecting Your Shower The video provides visual guidance for installing a barrier-free five-piece shower, emphasizing the importance of inspecting the unit upon arrival and noting any damage.
  2. 1:32 Dry Assembling Your Modular Shower The installer dry assembles the modular shower in an open space to ensure correct panels, drain location, and proper alignment before moving it to the bathroom.
  3. 3:04 Preparing the Framing Pocket and Subfloor The installer checks the framing pocket for proper sizing, squareness, plumb, and level, making necessary adjustments and inspecting the subfloor for integrity.
  4. 4:05 Installing the Shower Pan and Drain The installer cleans the pocket, dry fits and levels the pan, installs the drain body, and adheres the pan to the subfloor using silicone adhesive and bracing.
  5. 7:40 Assembling and Securing Shower Panels The installer places protection on the floor, caulks the pan ledge, and installs the lower and upper back panels, securing them to the studs.
  6. 8:31 Installing the Valve Wall and Plumbing The installer caulks the pan ledge and vertical back wall seam, sets the panel, drills holes for the valve and supply outlet, and connects the PEX supply lines.
  7. 11:05 Adding Accessories and Finishing Touches The installer marks, drills, and caulks around pilot holes for accessories, then caulks all seams and the front edge of the threshold, recommending a water retainer and shower curtain.
Chapters in this video
  1. 0:00 Receiving and Inspecting Your Shower This chapter explains how to receive and inspect your shower unit upon arrival, including what to do if there is damage.
  2. 1:17 Dry Assembling Your Shower This chapter demonstrates how to dry assemble your modular shower to ensure all panels and the drain are correct and undamaged.
  3. 2:49 Preparing the Framing Pocket This chapter shows how to check and adjust the framing pocket for proper sizing, squareness, plumb, and level.
  4. 5:02 Installing the Drain Body This chapter guides you through installing the drain body and preparing the drain to meet local plumbing codes.
  5. 5:44 Permanently Installing the Base This chapter details how to permanently install the shower base, ensuring it is level and properly supported.
  6. 8:12 Installing the Wall Panels This chapter demonstrates installing the wall panels using the pin and slot system, starting with the wall opposite the valve.
  7. 9:13 Installing the Valve and Wall This chapter shows how to install the valve and then the valve wall panel, including connecting the water supply lines.
  8. 11:13 Finishing and Sealing the Shower This chapter covers installing surface mount accessories, caulking all seams, and the option of adding a flange trim molding kit.
Chapters in this video
  1. 0:00 Introduction to Low-Threshold Shower Installation This video provides visual guidance for installing a low-threshold 3-piece shower, emphasizing the importance of referring to the installation manual.
  2. 0:24 Dry Assembly and Pre-Installation Checks The installer dry assembles the modular shower to ensure correct panels, drain location, and proper alignment before moving it into the bathroom space.
  3. 1:54 Preparing the Framing Pocket and Subfloor The installer checks the framing pocket for proper sizing, square, plumb, and level, making necessary adjustments and inspecting the subfloor for integrity.
  4. 4:07 Installing the Drain Body and Base Support The installer installs the drain body, prepares the drain to meet local plumbing codes, and applies silicone adhesive for proper support and adhesion of the base.
  5. 5:53 Permanently Installing and Securing the Base The installer permanently positions and levels the shower base, securing it to all available studs and cutting the drain pipe even with the rubber gasket.
  6. 7:22 Installing the Wall Panels and Valve The installer installs the wall panels using a pin and slot system, then installs the valve, connecting the hot and cold water supply lines.
  7. 10:19 Finishing Touches and Accessories The installer caulks all seams, recommends client involvement for accessory placement, and suggests an optional flange trim molding kit for a seamless transition.

Common Questions

Do I measure the shower alcove between the studs or at the finished wall?
Both. The base sits against the framing once finish materials are removed, so the stud-to-stud width and the depth from the back studs are the figures to frame from. Measuring the finished opening with your contractor as well shows how much tile or surround will be removed.
How do I measure where the shower drain needs to be?
Have your plumber measure from the center of the existing drain pipe to the framing behind it and to the framing on the nearer side wall. Compare those two figures with the back-wall and side-wall distances on the Specification drawing for your model and drain position. Say whether you need a left, right or center drain, because each has its own numbers.
Can an Ella shower base be cut down if my measurement is off?
No. The acrylic shell and foam reinforcement are molded together, and cutting into them on site is not possible. Measure the finished opening with your contractor, decide on the drain position, and give those figures with your order so the base arrives at the exact size you need.
What if my existing drain does not line up with the base?
You have two options. A licensed plumber can relocate the drain line, which is routine in a remodel when the floor is open. If moving the drain is impractical, ask about a custom-size base with the drain positioned to suit your existing line.
Does the shower base need a mortar bed under it?
No. The foam-reinforced base is designed to bear on a hard, level surface, so it sits directly on a flat subfloor or a concrete floor. Correct any dips with self-leveling compound rather than a mud bed, then dry fit the base and confirm it is level.

Related guides

Did this solve your question?

If not, open a ticket and our team will pick it up from here.

Open a Support Ticket