Is the Ella Shower Base Solid Underneath, and Why Does It Rock?

No. The underside of an Ella low-threshold shower base is not a flat solid slab. The floor is molded with a slight slope toward the drain, and a molded shim at the back brings the base level on a flat subfloor. That shape is why an uneven subfloor shows up as a base that rocks, and the fix is the site-cut wedges described in Shower Stall Shims Are Not Included: What Size to Make and How to Level the Base.

How the Base Is Built Underneath

The floor of the stall slopes gently into the drain so water does not pool on the surface. To keep the finished floor level despite that slope, the base has a molded shim at the rear that sets it level on a flat subfloor. Because the base bears on that slope and rear support rather than on a solid block, it has less tolerance for a subfloor that dips, humps or runs out of level. Any low spot under the base becomes a gap, and any gap lets the base rock.

Why a Rocking Base Is a Leveling Problem, Not a Defect

A base that rocks in the alcove is telling you the subfloor is not flat, not that the base is faulty. Check the floor with a level before the unit goes in, then set the base and slide wedge shims into any gaps beneath it. A base that is fastened to the studs before it is level has to come back out to be corrected, which is far more work than checking it at the start.

Shims, Not Mortar

A mortar bed is not required for the low-threshold stalls. Setting the base in mortar applies only to Ella's barrier-free roll-in showers. The low-threshold one-piece and three-piece stalls are leveled on wedges under the base, exactly as the instruction sheet specifies, which also removes the worry about mortar finding its way down the drain pipe.

Making the Shims

Shim blocks are not included with the stall. Cut wedge-shaped shims about 6 inches long, with the thick end 1 1/2 inches and tapering toward the other end. Cut several, because the number you need depends on how far out of level the floor is, and have them ready before the unit goes into the alcove.

Leveling the Base Before It Is Fastened

• Dry fit the unit in the alcove to confirm the drain location, the fit against the studs and the alignment of the pieces.
• Check the floor with a level and the walls with a level or plumb line, and correct both before the unit goes in.
• Set the base in place and slide shims into any gaps beneath it until it no longer rocks.
• Check level front to back and side to side, and adjust the shims until the bubble is centered in both directions.
• Fasten the unit to the studs as the instruction sheet describes, then recheck level after the last screw.
• On three-piece units, set the wall panels only after the base is level and fastened.

When the Seams Do Not Line Up

On a three-piece unit, seams that are even at one end and open at the other usually mean the base is out of level or a stud wall is pushing on a panel corner. Check the base for level first, then check each wall for plumb, and correct the wall so it no longer pushes on the panel before securing anything.

Getting Help During the Install

Ella does not perform installations, but free technical support is available to whoever is doing the work. Your installer is welcome to call (800) 480-6850 with the unit in front of them. Having the model number and a couple of photos of the alcove ready makes that call short.

Related Guides

• Installing Ella Shower Bases, the Flexible Shower Dam, and Shower Walls
• Common Installation Questions: Tile Order, Leveling Legs, Subfloor, Panels, Drain Size and the Outdoor Test
• Shower Base Sizes and Thresholds Compared: AcrylX Barrier-Free, SMC Linear-Drain, Molded-Seat and Cultured Marble Bases

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Common Questions

Is the bottom of the Ella shower base solid? No. The floor is molded with a slight slope into the drain and has a shim at the back that levels the base on a flat subfloor.

Why does my shower base rock in the alcove? The subfloor is not flat or level under the base. Slide wedge shims into the gaps until the base sits still and reads level in both directions.

Do I need to set the shower base in mortar? No. A mortar bed applies only to barrier-free roll-in showers. Low-threshold stalls are leveled on shims and are not set in mortar.

What size shims should I cut for the shower base? Cut wedges about 6 inches long with a 1 1/2 inch thick end. Make several so you can stack or swap them as needed.

Can my contractor call Ella while leveling the base? Yes. Free technical support is available to your installer at (800) 480-6850. Have the model number and photos of the alcove ready.