What Is Universal Design for ADUs?

By Buz Artiano, BuildX | October 2025

When families call us about building an ADU for aging parents or adult children, their main question is "How do we build something that works now and still works in 20 years?" The answer is in the design. We build in a way that creates spaces anyone can use, even if they are aging and have limited mobility.

At BuildX, we have built dozens of ADUs across Massachusetts with these special types of universal designs built in from day one. Families who do it this way will often avoid up to $35,000 in retrofits just because we put in $6,300 in well thought out features during the construction. The numbers always work, and it makes life infinitely easier.

What Does Universal Design Actually Mean for Your ADU?

Universal design means building your ADU so it works for toddlers, adults, and grandparents from day one. Every doorway is wide enough and every shower is big enough to accommodate a wheelchair. Every wall has blocking so grab bars can be installed in ten minutes, not 2 weeks and thousands of dollars later.

The goal is that whoever lives in the ADU can stay there as long as they want. We're not building just for today's needs. We are building a home that adapts as your needs change over the years.

What Are the Core Universal Design Features?

We recommend five essential features for every ADU we build:

Covered Entryway with Zero-Step Access. One of the entryways needs to be covered and have the deck surface flush with the door threshold. If you need a ramp later, we can add it easily without wrecking the deck. The covering keeps that flush connection from breaking down in the weather.

36-Inch Doors Throughout. Every interior door should be at least 32 inches wide, but 36 inches is better. A standard 30-inch door isn't wide enough for a wheelchair or walker. So we put 36-inch doors as standard in all our ADUs.

Accessible Bathroom Configuration. The bathroom has to have enough room between the toilet and walls for transfers from a wheelchair or walker. We place these things in a way so someone can move freely, with at least 42 inches of clearance wherever we can.

Wall Blocking for Future Grab Bars. Instead of relying on studs that are never where you need them to be, we install 2x8 or 2x10 blocking at 32 to 36 inches high, running all the way along bathroom walls, hallways, kitchens, and entryways. When it's time to put a grab bar, we can install it in ten minutes because we know exactly where the blocking is. We even have Matterport scans showing what is behind every wall to make it even easier.

Natural Light and Ceiling Height. Big windows all over the home improve livability and safety for people whose vision isn't what it used to be. We also recommend 9-foot ceilings when possible because they make smaller spaces feel so much larger.

How Much Does Universal Design Add to Construction Cost?

The investment is modest compared to the alternative.

Your only other option is to wait after someone falls, and then to go back and add all those features. And that's going to cost $35,000 or more, and assisted living facilities average $17,000 per month. One month of assisted living is almost three times what it would cost you to add all the recommended features to your ADU at the beginning.

Does Universal Design Make My ADU Look Medical?

People are always asking us this. Nobody wants their brand-new ADU to feel like a hospital room.

The truth is, we put a lot of thought into our design and the features are invisible. A curbless shower with a linear drain feels like being at a spa, not a facility of some kind. A 36-inch door feels open and spacious. Decorative grab bars look just like towel bars. Lowered window sills give you views that feel planned and intentional. Custom counter heights look like an expensive design feature.

Here's how we check our work. If a visitor walks in and says "why did they do that?" then we didn't do our job right. The features should make the space look better, not the other way around.

When Might Universal Design Not Be the Right Priority?

We build with universal design as a standard in every ADU. But we know that there are situations where someone might want to dial that back a bit.

If you've got a really tight budget and the ADU is going to be for someone who is young and healthy with no foreseeable mobility issues, you might go ahead and do standard 32-inch doors over 36-inch. If the site won't work for a covered entry without adding a bunch to the bill, you might leave that feature out.

All that being said, we never recommend you skip blocking because it costs almost nothing extra during construction. On that same note, roll-in showers don't cost much more than tub-shower combos. And since those two features alone handle around 80 percent of accessibility needs, we recommend them even on the tightest budgets.

How Do We Handle Grab Bar Installation?

We don't install the grab bars at random heights that we read from a code book. When the time comes for grab bars, we need the person who will be using them to stand in the room with us.

We will ask them to put their hand out like they are reaching for support. We make a note of their natural reach height, which is very different depending on the person. Then we screw the bar into the blocking at exactly the right spot. The whole process takes ten minutes because the blocking is already there.

If someone grabs a bar that isn't secured well enough to the wall and it tears out, they're going down, and aging people are more fragile than they once were. A toggle bolt in drywall will fail every time! Solid wood blocking will hold.

What Shower Units Work Best for Universal Design?

We only use one specific unit that's made in New York by Barrier Free. It is a heavy-duty acrylic unit (not vinyl, which is weak) with plywood backing pre-installed behind the walls. You can put a grab bar anywhere you want because there's solid backing that you can screw into anywhere.

Our standard unit has about a 5/8-inch lip to step over. Which is small enough that a wheelchair can go right over it, but just high enough to contain water. Completely flat roll-in showers end up pouring a lot of water on the floor and creates all new safety issues.

Ready to Build an ADU That Adapts With Your Family?

Universal design is not about building for disability. It is about building once and building right. The $6,300 investment in thoughtful features today prevents the $35,000 emergency renovation later, and it might prevent the $17,000 per month institutional alternative entirely.

We carefully check out every site for universal design opportunities as part of our process. We don't charge extra for this, and it happens automatically because we believe everyone deserves an ADU that works for decades.