How Do I Measure for a Replacement Shower Pan or Base?

To measure for a replacement shower pan, take three sets of figures with your contractor: the width of the opening between the studs, the depth from the back studs to the front of the pan, and the distance from the center of your existing drain pipe to the back wall framing and to the nearer side wall framing. Ella bases are ordered in an exact size and drain position and cannot be trimmed on site, so these figures decide which base fits. The drain figures are compared with the Specification drawing for the base, as explained in Shower Drain Rough-In: How Far the Drain Sits From the Back Wall and Side Wall.

Measure the Opening to the Framing

The base sits against the framing once the old tub or pan and the finish materials are removed, so measure to the studs where possible rather than to tile or drywall. Record the width between the studs and the depth from the back studs to the front edge of where the pan will sit. Check the pocket for square, plumb and level while you are there. If the opening turns out wider than the base you choose, the extra space is furred out before installation. The specification drawing gives the exact opening and depth to frame for every model, and Ella Shower Rough Opening, Standing Area and Floor Width: What to Measure Before You Frame explains how to read it.

Locate the Drain

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. Every Ella base has its drain center dimensioned the same way on its Specification drawing, and the numbers change with the model and the drain position. Left, right and center drains are different figures, so always say which position you are ordering. As two examples from the drawings, one right-drain base lists the drain center 15 1/2 inches from the back wall, while one center-drain base places it 19 inches from the back wall and 24 inches from the side wall.

Compare your two measurements with the drawing. If they match within the tolerance your plumber is comfortable with, the base can be set over the existing line. If they do not, a licensed plumber can relocate the drain line while the floor is open, or you can ask about a custom-size base with the drain positioned to suit your line.

Check the Floor the Pan Will Sit on

Ella acrylic bases are reinforced underneath with high-density foam and sit directly on a flat, sound subfloor or on concrete. They are not set in a mortar or mud bed. Correct any dips with self-leveling compound before the base goes in, and confirm the base is level once it is set. The construction and setting steps are in What the Ella Acrylic Shower Base Is Made Of and How It Is Installed.

Order the Size That Is Made, Then Dry Fit

Standard sizes such as 60 by 30 and 60 by 33 inches are stocked, and other sizes are made to order with the drain placed where you specify. Because the drain position is molded in, 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 is the finished walking surface, with its slope, threshold and drain molded in, so it is never measured as a substrate for tile; see Can You Tile Over an Ella Acrylic Shower Base?.

Related Guides

• Custom-Size Shower Bases: Size Ranges, Threshold Options, Drain Placement Rules, Construction, and How to Request One
• Shower Base Sizes and Thresholds Compared: AcrylX Barrier-Free, SMC Linear-Drain, Molded-Seat and Cultured Marble Bases
• Installing Ella Shower Bases, the Flexible Shower Dam, and Shower Walls

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