The structural question comes first
To get a level entry you need somewhere for the slope to go. Over joists, that usually means sistering and recessing the subfloor within the shower footprint — which depends on joist depth, direction and whether they can be modified without compromising the floor. Where that is not viable, the alternative is raising the entire bathroom floor and accepting a transition at the door instead of at the shower.
- Joists running the wrong way relative to the shower can make recessing impractical
- Engineered joists generally cannot be notched or drilled outside the manufacturer's allowances
- Slab-on-grade homes — common in newer Kuna, Star and south Meridian construction — require slab cutting
- Raising the whole floor affects door undercuts, transitions and sometimes the toilet flange height
Drain type and slope
A centre point drain requires the floor to slope from four directions, which produces visible planes in a curbless pan. A linear drain at the back wall or across the entry lets the whole pan slope in one direction, which looks cleaner, suits large-format tile better and drains more predictably. That is why most curbless showers use one.
| Drain | Slope pattern | Suits |
|---|---|---|
| Centre point drain | Four planes to the middle | Small mosaic-tiled pans |
| Linear drain at back wall | Single plane | Large-format tile, level entries |
| Linear drain at entry | Single plane toward the opening | Very open showers where spray reaches the entry |
Keeping water in an open shower
With no curb, the shower's geometry does the containment work. A longer shower with the head aimed away from the opening will keep water in with nothing more than a fixed panel. A short one with a head near the entry will not, whatever glass is added. If the room forces a short shower, the honest answer is a low-profile curb or a return panel rather than pretending the layout will behave.
This guide reflects general construction practice and is educational. It is not a substitute for manufacturer instructions, adopted building codes, or the requirements of your local building authority. Verify anything affecting permits, code compliance or product warranties before relying on it.
Frequently asked questions
Sources and verification
- Tile Council of North America (TCNA) Handbook — curbless and barrier-free shower receptor methods.
- Manufacturer instructions for pre-sloped trays, linear drains and membrane systems.
- Local building department requirements for structural alterations, confirmed per project.
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