Quick answer
A curbless shower is a shower with no raised curb at its entry, so the bathroom floor continues into the shower at the same level and a sloped floor, usually toward a linear drain, keeps water inside the wet area.
It is also called a zero-threshold or barrier-free shower. Because there is no curb to hold water back, the subfloor is usually recessed, and waterproofing often extends beyond the shower onto the bathroom floor.
Quick facts
The key facts about Curbless Shower, with sources:
- Floor slope (2021 IRC)
- Not less than 1/4 inch per foot (2%) nor more than 1/2 inch per foot (4%) toward the drain 1
- Minimum shower size (2021 IRC)
- 900 square inches, at least 30 inches in each direction 1
- ADA roll-in size
- 30 inches wide by 60 inches deep minimum, with a 60-inch-wide entry 2
- ADA roll-in threshold
- 1/2 inch high maximum 2
Key takeaways
- A curbless shower trades a curb for slope: the floor itself, not a step, keeps water in.
- The 2021 IRC requires shower floors to slope between 1/4 and 1/2 inch per foot toward the drain.
- Most curbless builds need a recessed subfloor or slab, which is structural work in a framed floor.
- Waterproofing should run past the shower opening, because splash and runoff are not stopped by a curb.
- For accessibility, the ADA roll-in standard limits the threshold to 1/2 inch and sets a 30 by 60 inch minimum.
What makes a shower "curbless"
Most showers have a curb, a low wall at the entry that holds water in. A curbless shower removes it. You walk, or roll, straight from the bathroom floor into the shower with no step to trip on.
Without a curb, something else must keep water in. That job goes to the floor. The shower floor is sloped toward a drain, and the drain is placed and sized so water reaches it before it reaches the doorway. Many designs use a long linear drain across the back wall or across the entry.
The 2021 International Residential Code (IRC) already allows this. Its shower receptor rule applies the curb limits only "where a shower receptor has a finished curb threshold," so a shower without one is not ruled out 1.
The ADA Standards go further and note that 60-inch-wide showers with no curb can make a bathroom more usable, since the shower area doubles as maneuvering space 2.
A curbless shower is a design choice in bathroom remodeling, often part of accessibility remodeling or aging-in-place plans.
How a curbless shower keeps water in
Four things work together. Skip one and water reaches the bathroom floor.
- A recessed base. The shower area is set lower than the bathroom floor, so the sloped mortar bed or pre-sloped pan can start level with the floor at the entry. Manufacturer guides describe recessing the concrete or the wood subfloor for this 34.
- Slope to the drain. The floor falls toward the drain at 1/4 to 1/2 inch per foot under the 2021 IRC 1. A drain installer’s guide sets mortar at 1/4 inch per foot toward the drain 4.
- A drain in the right place. Laticrete’s manual places a linear drain either at the wall opposite the door, with the floor sloping from the door to the drain, or at the door, with the floor sloping from the room toward the drain 3.
- A continuous waterproof layer. A bonded membrane or liner lines the floor and laps up the walls. The IRC requires built-up shower floors to be lined, including with sheet membranes meeting ANSI A118.10 1. One drain maker recommends extending waterproofing across the bathroom floor and up the walls 4.
- Tile and groutFinish surface, flush with the bathroom floor at the entry
- Bonded waterproof membraneANSI A118.10 sheet or liquid, lapped up the walls
- Sloped mortar bed or pre-sloped pan1/4 to 1/2 inch per foot toward the drain
- Recessed subfloorLowered between or on the joists so the slope starts at floor level
- Floor framingStiff enough for tile; changes need structural review
The recess is what lets the floor slope to the drain without a step at the entry. Source: [1] [3]
The best design keeps the spray aimed away from the open side, uses a glass panel to block splash, and puts the drain where most water lands.
Types of curbless shower construction
| Type | How it works | Notes |
|---|---|---|
| Linear drain at the back wall | Floor slopes one way, from the entry to a trench drain at the far wall 3 | Lets large tiles run in one plane |
| Linear drain at the entry | Floor slopes from the room side toward a drain across the opening 3 | Catches water right at the threshold |
| Center point drain | Floor slopes from all sides to a center drain | Needs more slope cuts and smaller tiles |
| Mortar bed over recessed subfloor | Sloped mortar built on a lowered slab or subfloor 34 | Flexible shapes; skilled labor |
| Pre-sloped pan or foam tray | Factory-sloped panel set into the recess 3 | Faster and more consistent |
| Low-threshold (near-curbless) shower | A beveled lip of 1/2 inch or less 2 | Used where a full recess is not possible |
Curbless vs roll-in vs walk-in
"Curbless" describes the entry. "Roll-in" is an ADA term with set dimensions and features, including a 30 by 60 inch minimum and a threshold no higher than 1/2 inch. A "walk-in" shower may still have a curb. Ask which one a quote means.
Example: how deep the recess needs to be
This shows why curbless showers usually need a recess. The shower size and layer thicknesses are example numbers; the slope limits are from the 2021 IRC 1. Real depths come from the drain and pan maker’s instructions.
| Step | Figure | How it was worked out |
|---|---|---|
| Shower depth, entry to back-wall drain | 60 in (5 ft) | Example; also the ADA roll-in minimum depth 2 |
| Slope at the IRC minimum | 1/4 in per ft | 2021 IRC P2709.1 1 |
| Fall from entry to drain | 5 ft × 1/4 in = 1 1/4 in | Length × slope |
| Slope at the IRC maximum | 1/2 in per ft gives 2 1/2 in of fall | Upper limit 1 |
| Mortar at the drain (example) | About 1/4 in minimum where the mortar thins out | One maker’s modified mortar can feather to about 1/4 in 4 |
| Recess needed below floor level (example) | Roughly the fall plus the thinnest bed and membrane | So at least about 1 1/2 in in this example, before tile thickness differences |
Fall (inches) = Distance from entry to drain (feet) × Slope (inches per foot)
Distance- From the highest point at the entry to the drain
Slope- 1/4 to 1/2 inch per foot under the 2021 IRC
Add the thinnest allowed mortar or pan depth and the membrane to find the recess, using the product maker’s numbers.
Source: [1]
Even at the minimum slope, a 5-foot shower falls more than an inch. With no curb, that inch has to come from somewhere, and that is the recess. In a wood floor, lowering the subfloor that much usually means changing or reinforcing framing, which is a job for a professional and often an engineer.
Where curbless details show up on plans and quotes
On plans. Look for a floor section that shows the recess depth, the drain type and location, the slope, and how far the waterproofing extends past the shower. A plan that just says "curbless" leaves the hard parts unanswered.
On a quote. The bid should name the waterproofing system, the drain brand and length, who modifies the subfloor and framing, and whether a glass panel or screen is included. Compare bids on the same scope with our bathroom remodel cost calculator and quote tools.
At inspection. Many jurisdictions check a shower pan or liner before tile, sometimes with a flood test. Ask your inspector what they need. Our permits and approvals guide explains the general sequence.
In the floor plan. The ADA advisory notes a 60-inch-wide curbless shower can serve as maneuvering space 2, which can change how the whole bathroom is laid out.
Ask for a flood test
Before tile goes down, ask the installer to plug the drain and flood the waterproofed floor for the time the membrane maker or your inspector requires. A leak found then costs far less than one found under finished tile.
Benefits and drawbacks
Why people choose it
When curbless is hard to do
The hardest case is an upper-floor bathroom over wood joists that cannot be lowered without new framing. Cutting or notching joists to make a recess is structural and must be designed.
Laticrete’s manual also sets floor stiffness limits for tile: deflection must not exceed L/360 for thin-bed ceramic tile or L/480 for thin-bed stone 3. A weakened floor will crack tile.
Slab floors are easier to plan in new construction, but cutting an existing slab means saw cutting, removal and possibly plumbing changes below.
Finally, the drain must be able to handle the shower’s flow. A short drain, a poor slope, or a spray aimed at the opening will send water onto the bathroom floor. Size and place the drain to the maker’s guidance.
What drives the cost of a curbless shower
We do not publish prices. The main cost drivers are the subfloor or slab work to create the recess, any framing changes and engineering, plumbing changes for the drain, the drain itself (linear drains cost more than point drains), the waterproofing system and how far it extends, tile size and layout, and the glass panel.
Converting an existing tub or curbed shower adds demolition and often floor repair.
Plan a contingency for hidden rot or old leaks found under the old shower. Our remodeling cost guide explains how to set one.
Life and warranty come mainly from the waterproofing system and the drain. Ask the membrane and drain makers what warranty applies, and what installation conditions it depends on, and get those terms in writing.
How a curbless shower is built in a remodel
This is the general order a contractor follows. The structural and plumbing steps are for licensed pros under a permit.
- Plan the layout: shower size (at least 900 square inches and 30 inches each way under the IRC), drain location, glass and spray direction 1.
- Check the floor structure. Have an engineer or qualified contractor plan any recess in wood framing; never cut joists without a design.
- Recess the slab or subfloor to the depth the drain and pan maker require 34.
- Set the drain and connect the waste line; plumbing work usually needs a permit.
- Build the slope at 1/4 to 1/2 inch per foot toward the drain, with mortar or a pre-sloped pan 14.
- Install the waterproof membrane, lapped up the walls and past the shower opening; flood test it 4.
- Tile, grout and set the drain grate flush; install the glass panel.
Keeping a curbless shower working
A curbless shower depends on its drain more than a curbed one.
- Clean the drain grate and trap often. Hair and soap slow drainage and push water toward the entry.
- Squeegee standing water toward the drain after showers.
- Inspect grout and sealant where the shower meets the bathroom floor and walls.
- Run the bath fan during and after showers to dry the room.
- Check the floor outside the shower for stains or loose tile, early signs of leaks.
Warning signs and when to call a pro
- Water pooling at the entry or reaching the bathroom floor during normal use.
- Slow drainage that does not improve after cleaning the grate.
- Loose, cracked or hollow-sounding tiles in or near the shower.
- Stains on the ceiling below an upper-floor bathroom.
- Musty smell or mold at baseboards near the shower.
Recessing a floor is structural work
Lowering a wood subfloor often means cutting into or reframing joists. Never cut, notch or drill joists without a design from an engineer or qualified professional and a permit. Also confirm wall reinforcement for future grab bars is installed before tile; the ADA Standards treat that reinforcement as the minimum in residential showers 2.
EPA advises drying water-damaged areas within 24 to 48 hours to prevent mold growth and fixing the water source 5. Call a licensed plumber for drain problems and a tile or waterproofing contractor for leaks.
Code and accessibility rules
Shower size (2021 IRC P2708.1). Shower compartments need at least 900 square inches of interior cross-section and at least 30 inches in minimum dimension, measured at the finished interior. Hinged shower doors must open outward 1.
Receptor floor (2021 IRC P2709.1). Where a shower receptor has a finished curb threshold, the curb must be at least 1 inch below the sides and back, and 2 to 9 inches deep from the top of the curb to the top of the drain.
The finished floor must slope uniformly toward the drain at not less than 1/4 inch per foot (2%) nor more than 1/2 inch per foot (4%), and floor drains must be flanged for a watertight joint 1.
Lining (2021 IRC P2709.2). Built-up shower receptors must be lined with sheet lead, sheet copper, plastic liner meeting ASTM D4068 or D4551, hot mopping, or a load-bearing bonded waterproof membrane meeting ANSI A118.10 1.
Accessibility (2010 ADA Standards 608). The ADA Standards apply to public and some multifamily settings, not most private homes, but they are the common benchmark.
Standard roll-in showers are at least 30 inches wide by 60 inches deep with a 60-inch-wide entry (608.2.2); roll-in thresholds are 1/2 inch high maximum (608.7); and a hand-held spray unit with at least a 59-inch hose is required (608.6) 2.
Adoption. States and cities adopt plumbing codes on their own schedule; some use the IRC plumbing chapters, others a separate plumbing code. Check with your building department or our permit checker.
Curbless shower vs. other shower types
| Shower type | Entry | Main difference |
|---|---|---|
| Curbless shower | Level with the floor | Slope and drain keep water in |
| Curbed shower | A curb 2 to 9 inches deep from top to drain 1 | The curb holds water; easier to build on any floor |
| Shower curb (low-profile) | A short, beveled curb | A middle path where a full recess is not possible |
| ADA roll-in shower | Threshold 1/2 inch maximum 2 | Set dimensions and features for wheelchair access |
| ADA transfer shower | 36 by 36 inch stall; threshold 1/2 inch maximum, beveled or rounded 2 | Designed for transfer to a seat, not roll-in |
Myths about curbless showers
- Myth Curbless showers are against code.
- Reality The 2021 IRC curb rules apply only where a receptor has a curb threshold 1; the slope and lining rules still apply.
- Myth Any shower can go curbless by removing the curb.
- Reality Without a recess, the slope would start above the bathroom floor; manufacturer guides call for a recessed slab or subfloor 34.
- Myth A curbless shower must be ADA compliant.
- Reality Private homes generally are not bound by the ADA Standards; roll-in specs are a benchmark you can choose to follow 2.
- Myth A flatter floor drains just as well.
- Reality The IRC sets a 1/4 inch per foot minimum for a reason 1; flatter floors leave water standing.
- Myth Waterproofing the shower area is enough.
- Reality With no curb, one drain maker recommends extending waterproofing across the bathroom floor 4.
What varies by location
There is no climate variable for a shower, but there is a regulatory one: which plumbing code your jurisdiction adopted and whether it inspects shower pans.
Some places use the IRC plumbing chapters, with the 1/4 to 1/2 inch per foot slope and lining rules quoted above 1; others adopt a separate plumbing code with its own wording.
Accessibility rules also differ: the ADA Standards govern public and some multifamily buildings, while state rules may apply to certain housing 2. Ask your building department which code and inspections apply before design is final.
When a curbless shower is the right choice
Choose curbless when someone in the home uses a walker or wheelchair, when you plan to age in place, or when you want a larger, open bathroom feel. It is easiest on a slab or in a bathroom where the floor framing can be lowered or is being rebuilt anyway.
A low-profile curb may be smarter on an upper floor with shallow joists, or when budget is tight and the structure cannot be changed.
Your next step: ask a contractor to check your floor structure first, then design the slope, drain and waterproofing as one system.
- If Bathroom on a slab, or framing is being rebuilt
- Then Good candidate; plan the recess with the drain maker’s specs
- If Upper floor over joists that cannot be lowered
- Then Consider a low-profile curb or engineered reframing
- If Wheelchair user in the home
- Then Use ADA roll-in dimensions as your benchmark
- If Tight budget, no structural changes
- Then A curbed or low-threshold shower is simpler
Questions about Curbless Shower
Do curbless showers leak?
They do not leak if the slope, drain and waterproofing are built correctly.
With no curb, water control depends on a floor sloped at 1/4 to 1/2 inch per foot, a drain sized and placed for the shower, and a membrane that extends past the opening.
Most problems come from too little slope or a poorly placed drain.
How much slope does a curbless shower need?
Under the 2021 IRC, a shower floor must slope uniformly toward the drain at not less than 1/4 inch per foot and not more than 1/2 inch per foot. Over a 5-foot-deep shower, that is a fall of 1 1/4 to 2 1/2 inches, which is why curbless showers usually need a recessed floor.
Do you have to lower the floor for a curbless shower?
Usually, yes. Manufacturer guides describe recessing the concrete slab or the wood subfloor so the sloped bed or pan starts level with the bathroom floor. In a framed floor this can mean cutting into or reframing joists, which needs an engineer’s design and a permit.
What size does a curbless shower need to be?
The 2021 IRC requires at least 900 square inches and 30 inches in each direction for any shower. For wheelchair use, the ADA roll-in benchmark is at least 30 inches wide by 60 inches deep with a 60-inch-wide entry. Larger showers keep more spray away from the opening.
Do curbless showers need a linear drain?
No, but linear drains are common because they let the floor slope in one direction. Laticrete’s manual shows linear drains at the wall opposite the door or at the door. A center point drain also works, but needs the floor sloped from all sides.
Is a curbless shower ADA compliant?
Only if it meets the ADA roll-in or transfer shower specs, such as a 1/2-inch maximum threshold, minimum sizes, grab bars, controls and a hand-held spray unit. Most private homes are not required to meet the ADA Standards, but they are a useful guide for accessible design.
Does a curbless shower need a glass door?
Not always. Many use a fixed glass panel to block spray while leaving the entry open. The 2021 IRC says hinged shower doors must open outward. Spray direction, shower size and drain placement matter more than whether there is a door.
Can a tub be converted to a curbless shower?
Often, yes, but it is more than a swap. The floor must be recessed, the drain moved and re-plumbed, and waterproofing extended. On a slab it is simpler than on an upper floor. Have a contractor check the structure and plumbing before you commit.
How do you keep water from leaving a curbless shower?
Use enough slope, a well-placed drain, and a glass panel to block spray. Aim the shower head away from the entry, and consider a linear drain across the entry in tight spaces. Extend waterproofing past the opening so any water that escapes cannot reach the subfloor.
Sources
- ICC, 2021 International Residential Code, Chapter 27 Plumbing Fixtures (P2708.1, P2709.1, P2709.2), retrieved .
- U.S. Access Board, ADA Accessibility Standards (2010), Section 608 Shower Compartments, retrieved .
- LATICRETE, Barrier Free Shower Assemblies Installation Manual (DS 012.5), retrieved .
- QM Drain, Flange Edge Linear Drain Installation Manual (curbless bracket kit recess), retrieved .
- U.S. EPA, A Brief Guide to Mold, Moisture and Your Home, retrieved .
Expert review
Written by the HyreRemodel Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Shower size, slope, curb and lining rules were read from 2021 IRC Sections P2708.1, P2709.1 and P2709.2 on ICC Digital Codes.
Roll-in and transfer shower specs come from Section 608 of the 2010 ADA Standards on the U.S. Access Board site. Recess, drain placement, deflection and mortar details come from the Laticrete and QM Drain installation manuals.
The recess-depth example is our arithmetic on example dimensions, labelled as such. No prices are given.
Suggest a correction. We fix errors and say what changed.