Is a Curbless Shower Worth It in an ADU, or Should You Buy the $3,000 One-Piece Unit?

By Buz Artiano, BuildX | November 2026

Watch: ADUs Explained by an Architect Who Actually Designs Them: Christine Monaghan

When you're planning a small home for a parent who's getting older, almost every photo about accessibility looks the same: a flat, open shower with no step at all. Then you get a quote and the difference between that shower and a standard one-piece unit is enough to make you question the entire bathroom. You want to make it right for the person who'll live there, but you don't want to pay an expensive premium for something that isn't worth it.

My name is Buz Artiano, founder of BuildX. We've built dozens of ADUs across Massachusetts, with most of them on the South Shore, and we handle design, permitting, and construction under one roof. Every one of those projects has the same set of limits: septic capacity, setbacks, and the state's by-right size cap, which keeps ADU bathrooms small enough that the choice of a shower can have a large effect on the budget.

We talked about this exact thing on the BuildX podcast with Christine Monaghan. Christine is an architect with 27 years of experience, and she designs ADUs for older clients. We've built a lot of these ADUs and in our opinion, the one worth paying for is going to fit how that person uses it on a daily basis. It should deal with water in a small space and not take up a huge amount of the budget.

Is a Curbless Shower Worth the Premium in an ADU?

For most ADU budgets, the expense is hard to justify. A fully curbless shower is high-end with a lot of floor work that has to be done, and for many of those who walk in or shower with help, a shower with a very small step is the thing to price first. A threshold is the lip or curb that you step over to get into the shower. Whether or not a threshold will work depends on how the person moves, so you should check on that with their caregivers.

Christine says this when we asked her about curbless showers: "I'm nervous about the flat to the floor one." What her company buys instead is a manufactured shower from a supplier out of New York, that has an entry step of about five-eighths of an inch. Her conclusion: "It's only about a five-eighths step up. So it's good enough."

So basically you've got three options. You've got a standard one-piece unit, you've got a shower that just has a low threshold like the one Christine talked about, and then there's a fully curbless tiled shower. The decision depends on four things: how the person will get into the shower, how much it costs, what effect it has on your floor, and how it handles water in a small room.

What Am I Paying For With Each Shower Option?

The price difference between these three showers is because of what happens underneath the bathroom floor. A one-piece unit is a single molded shower that sits on the floor and connects to the drain, with a curb to hold the water in. A curbless shower has no curb so the floor of it has to sit level with the bathroom floor and slope down to the drain. These are all assembled differently, such as recessing the subfloor or raising the surrounding floor. On the curbless showers we talked about it means cutting into the floor joists, members that hold up the floor, and any framing change has to have an approved design before work starts.

The drain is a whole decision on its own. The tiled showers we compared had what's called a linear drain, which is a long skinny channel that goes on just one edge of the shower. The other ones we looked at just use a regular center drain.

These are figures that were told to us in our podcast, not quoted BuildX prices, and they weren't divided between the unit and the labor. Compare all three options on installed price before you decide.

When the subject came up on the podcast, our first reaction was honest: "That's expensive though. And you've got to cut into the floor joists. It's very expensive."

The floor framing is the part of the price nobody sees in a photograph. The kind of tile and drain choices are finishes, and you can always trade them for a different one that's more or less expensive. Whatever method the design uses, the floor under that shower is going to be built differently than the floor around it. So that's why we decide on the type of shower during the design phase, before the floor is framed. That way the floor work is part of the approved plan from the first. Changing your mind after the floor system is built turns a finish decision into a rework.

How Does a Curbless Shower Handle Water in a Small Bathroom?

Containing the water is the tradeoff Christine brought up. Manufacturers make curbless pans that taper down toward the drain, and her experience has been that "no matter what you do, you're going to get a lot of water on the floor." That's just one architect's observation. How a specific curbless shower will perform depends on its slope, the drain and the layout that's around it.

In a small ADU bathroom, the shower, the vanity, and the toilet are all close together, so any water that gets outside the shower will end up where your parent walks next. Just a small step can give that water an edge to stop against.

Will a Five-Eighths Inch Step Work for Someone in a Wheelchair?

That depends on how the person will be getting into the shower. Christine's thoughts are from her own older clients: "If someone's in a wheelchair, they're generally going to have to have someone help them get in there anyways." For clients who get into the shower with the help of a caregiver, she said that "that little five-eighths is not going to kill the roll over." Because a caregiver is there doesn't settle which specific threshold works for someone, so think of her five-eighths inch step as a starting point to check out.

That reasoning won't work for someone in a wheelchair who's by themselves. A person who uses a wheelchair independently will need a lower threshold than the one Christine specifies, and so that can move a curbless design to the top of the list. We're not saying that a five-eighths inch step will always meet whatever standard that you need. If a doctor, insurance, or program you use requires that you do something different than that, just bring us the details for whatever they require to the first design meeting so we can design it exactly how you need.

Christine also builds for needs the person doesn't have yet. Her advice to every client, "even if they're younger," is to "future proof this the best that we can," including "lots of blocking in the walls for future grab bars." Blocking is solid wood framed into the wall space so that a grab bar can be installed later without opening the wall.

How Much Bathroom Fits Inside a 900 Square Foot ADU?

Massachusetts allows an ADU by right up to 900 square feet or half the gross floor area of the main house, whichever one is smaller. But there can always be other local building, health, and dimensional rules that your town can impose on top of the state's rules. All the information you need is at mass.gov.

That cap on the size will determine every room, and the bathroom most of all. As we told Christine, "you're still boxed in by that 900 square feet," and her answer was simple: "Which makes small bathrooms." Most families who want two bedrooms also want to have a bath and a half, and you can make it work but it's tight. Sometimes the room to do a curbless shower the right way isn't there at all.

Should My Parent's ADU Have a Tub Instead of a Shower?

Christine sometimes hears this request from her own older clients: "I have some clients that are older and they're like, I really want a tub. I'm like, I don't think it's a good idea." A tub wall is a much taller step than five-eighths of an inch, and it will have to be stepped over while the person is wet, which is exactly what an accessible bathroom is meant to eliminate.

This one principle covers the whole bathroom: "You can never tell what someone's going to really need." Grab-bar blocking that's already in the walls gives you room to add support when needs change, no matter which shower you choose.

When Does a Curbless Shower Make Sense?

Since we're pricing these showers, you'd expect us to push whichever option will keep the project moving. The truth is, we like building curbless showers. A linear drain is a beautiful detail.

Curbless is the right option when the person using the shower has to roll into it on their own. Beyond that, it will fit when there are these three conditions:

• The budget pays for the floor work with cutting quality somewhere else in the ADU.
• The bathroom has room for the layout without taking space away from the bedroom or kitchen.
• The design has a way to handle water at the open edge with slope, drain placement, and finishes.

If those are all true, then a curbless shower is a good choice, and it should be in the plan from the very first. If they don't, the low-threshold unit is the other option to price first for a parent or can walk in or transfer with help. Ask every builder how they set the floor under the shower.

Ready to Price the Right Shower for Your ADU Bathroom?

For a parent who doesn't need help showering and is able to walk into the shower, the low-threshold shower is what you should look into first, once their care team checks the step. For someone who has to roll in, but doesn't need any help, curbless is what you should start with.