What is a shower dam and when do you need one?

A shower dam is a flexible, self-adhesive rubber strip fixed across the open entry of a curb-less shower base. It does the job a curb would do: when a wheelchair or walker rolls over it the strip flattens, and once the wheel passes it springs back to its original shape and holds the water in the stall. You need one whenever the base has no threshold to hold water back, which is why the collapsible rubber dam comes standard with Ella's roll-in barrier-free bases and is not part of a stall with a raised edge. What is a roll-in shower and who should get one? covers the base the dam belongs with.

What the Dam Is and the Names It Goes by

Ella's guides call the same part a collapsible rubber dam, a water retainer, a flexible shower dam and a collapsible threshold. The video on this page presents it as the Ella flexible shower dam for exclusive use with a barrier-free wheelchair accessible shower base, and describes it as flexible, compressible and waterproof. It arrives as a length of rubber with an adhesive strip under a red tape cover, plus plastic end caps for the cut ends, and it is finished with a thin bead of silicone along both lower edges. The video shows wheels rolling over it on the way in and out, the dam returning to shape, and then a demonstration of how effectively it contains water in the stall.

The dam matters because of how a roll-in shower is built. As What is a roll-in shower for wheelchair users? explains, a curb-less pan has no lip at all, so the wheels of a wheelchair, a walker or a shower chair pass from the bathroom floor into the shower without being lifted. Without a curb, something else has to hold the water in, and that something is the dam, working together with the slope molded into the floor of the base that carries water to the drain.

Which Ella Bases Need a Dam and Which Do Not

The deciding factor is the height of the entry, not the footprint of the base. Every threshold figure below appears on a published Ella page. Where a page does not say whether a dam is included, the cell says not listed rather than guessing.

What the table means: the taller the threshold, the more of a step it is for someone with limited mobility, and the lower the threshold, the more the design relies on the floor slope, the drain and, at zero threshold, a dam to keep water where it belongs. A 3/4 inch step and a flush floor can look alike in a product photo, so the threshold figure on the spec sheet should drive the decision. If the person bathing stays seated in a wheelchair or shower chair, or a walker or foot tends to catch on a lip, the roll-in base with its dam is the right choice. If they can comfortably step over an edge, a base with a threshold holds the water without a dam, and Ella offers the 3 inch step-in threshold for anyone who prefers a slightly raised edge.

How the Dam Is Installed, Step by Step

The video shows the full sequence on a barrier-free base, and the order matters because the adhesive gets one chance to bond cleanly.

1. Measure precisely, then clean all surfaces thoroughly with denatured alcohol.
2. Lay a tape line on the surface as a guide, measure how much material is needed, mark it and cut carefully.
3. Insert the plastic end cap as indicated and apply silicone to all gaps.
4. Pull the red tape backing away about an inch, set the dam down snugly against the shower wall and floor, and peel the backing away slowly as you work down the length.
5. Press firmly along the entire length so the adhesive bonds, then remove the tape guide and clean all surfaces again.
6. Run painter's tape down both sides of the dam, apply a thin bead of silicone along the lower edge on both sides, smooth it, and silicone both end caps so every gap is sealed.

Two rules protect the base and its warranty. On a tile floor, the grout line beneath the dam must be caulked so water cannot travel under the strip. And the threshold of the base must never be drilled, because drilling the threshold voids the base warranty; the dam is held by its adhesive and the silicone, never by screws. A local licensed installer handles the work, and your Ella dealer or the team at (800) 480-6850 can answer questions about the base itself.

Depth, Drainage and the Standard That Applies

People often ask how deep a shower pan is when what they need is the threshold height, because depth has nothing to do with drainage. Every Ella base has a textured, slip-resistant floor with the slope and drainage channels molded in, so water is carried to the drain by the shape of the floor, and a 2 inch threshold drains the same way a 4 inch one does. How Deep Is a Shower Pan and Does Depth Matter? works through that distinction, and What Are the Standard Shower Base Sizes Ella's Bubbles Makes? lists the 30 by 60, 32 by 60 and 36 by 60 inch footprints the roll-in and standard bases share, each with a left or right drain. What does matter for a curb-less stall is where the drain sits, so tell the team where your existing drain line is in the floor before choosing a size.

Where a project must meet an accessibility standard, the reference figure is the ADA limit of 1/2 inch for the threshold of a roll-in shower compartment, which is why the barrier-free line with its dam is the one an architect, facility or inspector will look at. What is a roll-in shower and who is it designed for? explains who the roll-in base suits, from wheelchair and walker users to caregiver-assisted bathing and commercial projects. State and local codes decide what passes inspection, so confirm the standard that applies with your local building department before the base is ordered.

Watch: The Ella Shower Dam, Keep Water In, Roll In With Ease | Ella's Bubbles with chapters and a full transcript.

Related Guides

• What is a roll-in shower and how does it work?
• Installing the SMC Low-Profile Shower Bases: 1 Inch Reversible Linear Drain and Barrier-Free Linear-Drain Bases
• Installing Ella Shower Bases, the Flexible Shower Dam, and Shower Walls

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