Does Drywall or Backer Board Go Over the Walk-In Tub Flange?

Neither one goes over the flange. On an Ella walk-in tub the wall board, whether drywall or cement backer board, sits behind the tile flange, and it is the finished surface, the tile or the wall panel, that comes down over the flange and onto the flat deck. The cross-section in the Standard 30x52 installation manual draws the order from back to front as stud, drywall, tile flange, then tile or wall panel, with silicone-based caulking sealing the joints. The flange, the silicone and the wall finishing choices are covered in Tile Flange, Caulking, and Finishing the Walls Around Your Walk-In Tub; this page is about the layer order and what to settle before the walls close.

Why the Flange Sits in Front of the Wall Board

Ella walk-in tub shells do not come with a built-in tile flange; they have a flat deck edge. The flange is added at installation, and Ella recommends its glue-up Flexible Tile Flange, which bonds to the edge of the tub rather than to the wall. That one fact settles the question. Because the flange is part of the tub, the wall board can only be behind it, and the finish is what laps over it. The strip is thin, 1/8 inch or 3/16 inch if you source your own in acrylic, thin stainless steel or a fiberglass strip, approximately 5 inches tall, and glued to the tub edge so that it overlaps the edge by about 2 inches, which leaves the rest standing up against the wall face as the water barrier. Ella's kit is a 124 inch long strip with a cleaning wipe and instructions, and because it is a small accessory it ships separately from the tub by parcel carrier.

Think about where water goes. Water running down the wall meets the tile or panel first, runs over the flange, and is shed back onto the deck and into the tub. If the wall board were in front of the flange, water would reach the board edge and the gap behind it instead, which is exactly the leak path the flange exists to close.

The Layers, Back to Front

1. The studs.
2. Drywall, or the backer board your installer chooses. The wall material behind the flange is the installer's call for the tile system being used; the manual's cross-section shows drywall.
3. The tile flange, glued to the tub edge with 100% silicone before the tub is pushed into place, overlapping the edge by about 2 inches with the rest standing up against the wall board.
4. The tile or wall panel, run down over the flange and onto the deck.
5. Silicone caulk at every joint where the finish meets the deck.

The table sorts the wall materials named in Ella's documents by where they sit in that order.

What the differences mean: the choice between drywall and backer board is about the finish you are putting on the wall, not about the flange. Whatever board your installer picks for the tile or panel system, the flange still bonds to the tub and the finish still runs over it. If you would like the team to look at a specific wall build-up, open a ticket at ellasbubbles.com/support with a photo or a sketch.

Finish These Before the Walls Close in

• Complete the pre-installation water test. Once tile or panels are up, reaching the tub to correct anything means opening the wall.
• Confirm the tub is level with every leveling leg touching the floor. The flange is glued to a tub that is already in its final position.
• Measure the flange run: the back wall plus each end wall the tub sits against. A 52 inch tub with a 30 inch width set into a standard 60 inch alcove has a combined run of roughly 120 inches once the extension panel side is included, so one 124 inch strip normally covers it. For wider or longer tubs, corner installations with only two walls, or unusual layouts, measure first and ask for the length you need, mentioning your tub model so the fit can be confirmed.
• Clean the tub edge where the flange will sit so the silicone bonds well.
• Put in any backing for a wall-mounted seat or grab bar now. The published method sets 2x6 backer boards horizontally between the studs at the mounting height, level and centered where the bracket will land, fastened with structural screws, and only then completes the wall finish over them, as described in How do I add backing behind an acrylic shower wall for a seat?.

Panels and Tile over the Flange

Which finish goes over the flange changes the substrate but not the order. The SMC 12-piece subway kit is set bottom row first on 100 percent silicone over a clean, dry substrate of drywall, cement board or existing wall, and each panel has an integrated flange so the rows overlap without grout lines. The acrylic 3-panel kit is glued only, never screwed or nailed, dry-fitted first and braced or taped for 24 hours while the silicone cures, and it glues to drywall or over existing tile. Both are walked through in Installing the SMC 12-Piece Wall Kit, Acrylic Tub Surrounds, the 3-Panel Kit, Tongue-and-Groove Wall Tiles and Palisade Vinyl Tiles. For a walk-in tub that does not need floor-to-ceiling coverage, Ella also describes a 6-piece SMC kit at 48 inches high and a shorter 40 by 48 by 60 inch version of the 3-panel system as tub surrounds; the printed sizes are in Wall Kit Sizes at a Glance. Conventional tile over drywall or cement board follows the same rule: the flange goes on the tub first, the tile comes down over it onto the deck, and silicone finishes the joint.

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 I Caulk and Seal a Walk-In Tub Against the Walls?
• The pre-installation water test: catch leaks before your walls are finished

Related Videos

Common Questions