What is a shower flange and why does a shower pan need one?

A shower flange, often called a tile flange, is the upturned edge of a shower pan where the pan meets the walls. It sits behind the tile or wall panel, so water running down the wall is sent onto the pan instead of slipping behind the wall and into the framing. Ella walk-in tubs have a flat deck edge with no molded lip, and for tubs and shower bases that do not have a built-in flange, Ella offers the Glue-Up Flexible Tile Flange, which My Tub Has No Tile Lip. Which Flange Do I Use? covers for the walk-in tub. This page explains why a pan needs a flange, how the glue-up version goes on, how to seal the joint and choose a silicone color, and what a shower dam does that a flange does not.

Why a Shower Pan Needs a Flange

A watertight shower has two halves. The pan is one of them: an Ella acrylic base is a finished surface with its slope, threshold and drain molded in, so water that lands on it runs to the drain on its own. The other half is the joint where the pan meets the walls, and that joint is the flange's job. Water that runs down a wall has to end up on the pan. If the wall finish simply stopped at the top edge of the pan, every shower would push a little water into the seam between the two, and from there into the wall cavity and the subfloor, where it stays hidden until something swells, stains or rots. The flange turns the pan edge up behind the wall finish. Tile or wall panels come down over the flange, so any water that gets behind the surface of the wall meets the flange and runs back into the pan. Because the wall finish depends on that overlap, your installer plans the flange into the tile or panel work before the first course goes up, not after.

The same logic explains why an Ella acrylic base is never tiled over and why the tiled look belongs on the walls above it, coming down over the pan edge. Can You Tile Over an Ella Acrylic Shower Base? covers that side of the question.

Three Water Barriers on an Ella Shower, Compared

Ella products use three different edge details to keep water where it belongs, and they are often confused in searches. The table uses only figures printed in Ella's documents; where none is printed, the cell says not listed.

The flange and the dam solve different edges. The flange seals the edges that meet a wall; the dam closes the one edge that meets the room on a curb-less entry, where a wall and a flange cannot go. A roll-in shower may use both, one along the back and side walls and the other across the front. Ella's comparison of base families lists whether a tile flange is built in as one of the differences between them, alongside threshold height and drain style, so confirm which your base has before the wall finish is ordered. Shower Base Sizes and Thresholds Compared: AcrylX Barrier-Free, SMC Linear-Drain, Molded-Seat and Cultured Marble Bases sets out those families.

How the Glue-Up Flexible Tile Flange Goes on

Bonding the flange is work for your local licensed contractor, and the sequence matters as much as the material:

1. Set and level the tub or base first, with every leg bearing on the floor, and complete the water test before any wall is finished.
2. Measure the total run of edge that meets a wall, the back plus each end, at deck height, and match it to the kit length.
3. Clean the edge with the alcohol tissues supplied in the kit.
4. Bond the flange with 100 percent silicone so it overlaps the edge. The strip is reversible, and which colored side faces out depends on whether the fixture already has an integral flange.
5. Run the tile or wall panel down over the flange and onto the deck, then silicone every joint, including where any extension panel meets the tub and where an end panel meets the wall.

The membrane is thin, waterproof fabric rather than a rigid lip, and that is the point. Floors contract and expand and joints move over the life of a bathroom, and the flexible flange makes a seal that holds through that movement. For a shower base the same approach applies, and the strip can go on after the base is set.

Sealing the Joint and Choosing a Silicone Color

The gap between the tub or base and the flange is sealed with a neutral-curing, sanitary-grade, 100 percent silicone sealant. To get a clean bead, protect the tub or shower floor with painter's tape, run a bead of silicone into the joint between the floor and the wall, smooth it with the corner of a spatula, then remove the tape. Once the wall finish comes down over the flange, a second bead of silicone or other waterproof sealant goes between the tub floor and the tiles, so the finished shower has a sealed joint at the flange and a sealed joint at the visible edge.

For color, aim for a match with the fixture and the wall panels. Ella's ASI 502 100 percent RTV silicone for acrylic shower wall panels comes in Clear, White, Aluminum/Gray, Bronze, Almond and Black, and Ella suggests using the same caulk at the floor joint that you use on the panel seams so the color and the performance match throughout. If you are unsure which color suits your unit, share your model name and a photo through ellasbubbles.com/support, or call (800) 480-6850, and the team can help you choose.

What a Shower Dam Is

Searches for a shower dam usually mean the collapsible rubber dam on Ella's barrier-free roll-in bases. A roll-in base has a curb-less entry so a wheelchair or rolling shower chair moves straight in from the bathroom floor, and that leaves one open edge where water could run out into the room. The self-adhesive dam closes it. The wheels of a wheelchair simply roll over the compressible material entering or leaving, the dam returns to its original shape, and the water stays inside the shower stall. Every roll-in and barrier-free base ships with the dam, and the barrier-free package options include horizontal or vertical end caps for it. What is a roll-in shower and who needs one? explains who the curb-less entry is for.

A dam is not a substitute for a flange, and a flange is not a substitute for a dam. A low step-in threshold on a custom base keeps the water in at the front by being a step, which is why a low-threshold pan is not labeled roll-in; Custom-Size Shower Bases: Size Ranges, Threshold Options, Drain Placement Rules, Construction, and How to Request One explains that distinction. Whichever base you choose, the wall edges still need a flange, built in or glued up, before the walls are finished.

Related Guides

• The Glue-Up Tile Flange Kit: What Is in the Box, Which Length to Choose, Which Colored Side Faces Out, and Whether It Goes On Before or After Drywall
• How Do You Install a Tile Flange on a Tub or Shower Base?
• What Is a Tile Flange on a Walk-In Tub?

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