Curbless showers: what has to be true before you can have one

Curbless showers are the most requested thing in the bathrooms we design right now. No step, no ledge, one continuous floor. They look calm, they are easier to clean, and they make a bathroom easier to use as people get older.

They are also the bathroom detail most likely to be done badly. When a curbless shower fails, water ends up in the hallway or, worse, in the ceiling below.

Here is what has to be true before we will build one.

The floor has to be able to drop

Without a curb, water is kept in the shower by slope alone. That means the shower floor has to sit lower than the bathroom floor, which means recessing it into the structure.

In a house with wood joists, that usually involves modifying the framing in the shower area so the floor can drop. Sometimes the joists run the right way and this is straightforward. Sometimes they run the wrong way, or there is a beam, duct or drain stack in the way. We open the ceiling below or the floor above during design to find out, rather than guessing.

On a concrete slab in a basement, it means cutting and recessing the slab, which is very doable but has to be planned for.

The drain has to work with the slope

Linear drains along the back wall are our usual choice. They let the floor slope in one direction, which means you can use large-format tile without cutting it into a funnel shape. The drain needs to be sized for the shower head flow, especially with rain heads or multiple outlets.

Waterproofing has to be a full system

Tile and grout are not waterproof. Everything behind them is. In a curbless shower, we waterproof the shower floor and walls as one continuous system and carry the membrane well beyond the wet area onto the bathroom floor. Before any tile goes down, we flood test the floor and leave water standing to prove it holds.

If a contractor cannot tell you which waterproofing system they use and how they test it, that is your answer.

Glass and splash

Without a curb, a short glass panel can let water reach the bathroom floor. We size the glass to the shower head position and the room. A fixed panel that runs most of the shower length, or a slightly longer walk-in, keeps the floor outside dry.

When it is not worth it

Occasionally the structure makes a true curbless shower very expensive. In those cases we will tell you, and show you the alternatives: a very low curb, a reduced step, or putting the curbless shower in a different spot in the room. A good design solves the problem without forcing a detail that will not hold up.

When the conditions are right, a curbless shower is one of the nicest upgrades you can make to a bathroom. It just has to be built from the floor joists up, not from the tile down.