Why slabs make this different
In most of the country a curbless shower is easy: drop the subfloor between joists, slope it, done. Phoenix homes have no joists. The floor is a 4-inch concrete slab poured on grade, and the shower drain runs through it. To get a curbless entry you need the shower floor to sit about 1.5 to 2 inches lower than the bathroom floor at the drain, and there are only three ways to get that height.
First: find out if your slab is post-tension
How to tell: look at the garage slab edge or the exterior stem wall for a stamped warning like “POST TENSIONED SLAB, DO NOT CUT OR CORE”. Homes built after the mid-1990s in Gilbert, Chandler, Queen Creek, Peoria, Surprise and most of North Phoenix are commonly post-tension. Older ranch homes in Arcadia, central Phoenix, Tempe and Mesa are usually conventional rebar slabs. If there is no stamp, a GPR (ground-penetrating radar) scan costs $300–$500 and maps the cables so a drain can be moved safely between them. We scan before we cut, every time.
The three ways to build the slope
Option A: recess the slab (the true curbless)
Saw-cut the shower footprint, chip the concrete down 2 inches, re-pour a sloped mud bed to the drain. This gives a completely flush entry and works with any tile. It is the most labor and the most dust, and it is the one that requires the post-tension check. Adds $1,800–$3,500 to a standard walk-in shower.
Option B: raise the bathroom floor
Leave the slab alone and build the rest of the bathroom up 1.5 inches with a self-leveling underlayment or a thin sleeper system, so the shower ends up “lower” by comparison. Works well when you are redoing the whole bathroom floor anyway. Creates a small step at the bathroom door that a beveled transition handles. Adds $900–$2,000.
Option C: linear drain at the entry with a minimal slope
A trench-style linear drain across the shower opening lets the floor slope in one direction only, which needs less depth. Combined with a shallow recess or a slightly raised bathroom floor, you get a flush or near-flush entry with much less concrete work. Linear drains cost $400–$1,200 more than a center drain but are the reason most modern curbless showers look the way they do.
| Method | Entry | Concrete work | Adder | Best for |
|---|---|---|---|---|
| Recess slab | Fully flush | Heavy | $1,800–$3,500 | Primary baths, accessibility, forever homes |
| Raise bathroom floor | Flush inside room | None | $900–$2,000 | Full remodels replacing all floor tile |
| Linear drain + shallow slope | Flush or ¼-inch lip | Light | $1,200–$2,500 | Most Phoenix walk-in showers |
Moving the drain
Most tub-to-shower conversions keep the drain near where the tub drain was, which usually lands it at one end of the new shower, a fine spot for a linear drain. Moving a drain to the center or to the far wall means opening the slab along the path, tying into the existing line with the correct fall, and inspecting before the patch. Budget $1,200–$2,500 for a move under 4 feet on a conventional slab; more if the line has to go around post-tension cables. Cast-iron drain lines in 1960s–70s homes are sometimes deteriorated; if we find that, we replace the section and show you the photos.
Waterproofing: the part you will never see and must not skip
A curbless shower has no lip to stop water, so the waterproofing must extend past the shower into the bathroom floor, up every wall, and be continuous with the drain flange. We use bonded sheet-membrane systems (Schluter Kerdi or equivalent) with a matching drain, and we flood-test the pan for 24 hours before tile. Ask any contractor two questions: which waterproofing system, and do they flood-test. If the answer is “we use a good liner and a mud bed”, that is a curbed shower method being used on a curbless design, and it fails.
Containing the water
Slope of ¼ inch per foot toward the drain, a linear drain at the entry or the back wall, a fixed glass panel of at least 36 inches, and a rain head aimed away from the opening. With those four things, a curbless shower keeps a bathroom floor drier than most curbed ones.
Cost and timeline in Phoenix
A curbless walk-in shower in the Valley typically runs $9,800 to $24,000 for the shower itself, plus the concrete adder from the table above. Accessible builds with a bench, fold-down seat and grab bars in a matching finish land in the $9,500 to $28,000 range. Timeline is 5–8 working days: one for demo and scanning, one to two for concrete and drain work with inspection, one for waterproofing and the flood test, two to three for tile, then glass a week later after measuring.
Questions people ask
Can every Phoenix home have a curbless shower?
Almost every one. The method changes with the slab type. Post-tension slabs need a scan and usually the linear-drain approach; conventional slabs can be recessed directly.
Does a curbless shower flood the bathroom?
Not when it is built with proper slope, a linear drain and a fixed glass panel. The waterproofing extends into the room floor as a second safeguard.
How much more does curbless cost than a normal walk-in shower?
Usually $900–$3,500 more, depending on the method. It is the concrete and drain work, not the tile.
Is curbless only for accessibility?
No. It is the standard look in high-end primary baths in Scottsdale and Paradise Valley. Accessibility is a bonus that adds resale appeal in 55+ communities like Sun City.
Do I need a permit?
Yes when the drain moves or the slab is cut. Maricopa County or your city inspects the drain before we patch. We pull the permit and include it.
Related
Walk-In Shower Remodel · Accessible & Aging-in-Place Bath
Bathroom remodeling in Paradise Valley, Chandler, Sun City, and across the Valley. More guides: Bathroom Remodel Cost in Phoenix (2026) · Tile vs. Acrylic Showers in Arizona Heat · Does a Tub-to-Shower Conversion Hurt Resale in Phoenix? · Bathroom remodel permits · Walk-in showers for seniors.