5 Design Features Every ADU Needs When Building for Aging Parents

Nearly 70% of adults over 65 will need some form of long-term care in their lifetime — and most of them would far rather spend that time near family than in a facility. If you’re planning an accessory dwelling unit (ADU) for an aging parent, you’re making one of the most meaningful investments a family can make. But an ADU that wasn’t built with accessibility in mind can quickly become a safety liability. The good news? Adding the right design features from the start is significantly cheaper than retrofitting later — and in many cases, it’s the difference between a space your parent can age into for decades versus one that stops working for them in a few years.

At Lagace Construction, we’ve helped families across eastern Connecticut plan and build ADUs specifically designed for aging parents and multigenerational living. Here are the five design features we consider non-negotiable — and what each one actually costs to include.

1. No-Step Entry

This is the single most important feature in any accessible ADU, and it’s also the easiest to overlook when you’re in the planning phase. A no-step entry — also called a zero-threshold entry — means there’s no raised lip or step between the outside and the interior of the unit. Even a 1-inch threshold can pose a serious trip hazard for someone using a walker or wheelchair.

The design solution is straightforward: grade the approach walkway so it slopes gently toward the entrance, use a recessed entry mat or trench drain to manage water intrusion, and set the finished floor height flush with the exterior landing. This is dramatically easier to do during construction than after the fact, when it may require breaking concrete, rebuilding steps, or installing a ramp that can look tacked-on.

Cost to add during construction: $800–$2,500 depending on grading complexity. Cost to retrofit: $5,000–$15,000+ for a proper ramp or entry rebuild.

2. Wider Doorways (36″ Minimum)

Standard residential doorways are 32 inches wide — enough for a person, but not for a wheelchair or a two-wheeled walker (rollator). ADA-compliant doorways start at 36 inches clear, and we typically recommend 36″ as the minimum for any ADU intended for aging parents. For bathroom doorways, we often go to 42″ to allow for easier maneuvering.

Wider doorways don’t require major structural changes in most new ADU builds — it’s primarily a framing consideration. Where you do need to be thoughtful is the swing direction of doors. Inswing doors can block a person who has fallen just inside the room; an outswing door or a barn-style sliding door eliminates that problem and also makes better use of limited floor space in smaller ADUs.

Cost to upsize doorways during construction: $200–$500 per door in labor and framing. Cost to widen existing doorways later: $1,200–$3,500 per door depending on wall type.

3. Walk-In (Curbless) Shower

A traditional tub-shower combo is one of the most hazardous features in any home for an older adult. Stepping over a tub ledge — especially when wet — is a leading cause of bathroom falls. A curbless or roll-in shower eliminates that hazard entirely while also making the bathroom feel more open and modern.

The key is in the drain design: curbless showers use a linear drain or a center drain set into a slightly sloped floor to manage water without a curb to contain it. This requires careful coordination during the rough plumbing and tile-setting phases — the slope must be precise (typically ¼” per foot) and consistently executed. Done right, it’s seamless and attractive. Done wrong, it puddles outside the shower area.

For maximum future-proofing, size the shower at least 36″ × 36″, and ideally 60″ × 36″ or larger to allow a shower chair or caregiver assistance. A fold-down teak bench is a small add-on that provides enormous value.

Cost premium over standard shower during construction: $1,500–$4,000. Cost to retrofit later: $6,000–$14,000 due to tile removal and drain relocation.

4. Grab Bar Blocking in Walls

Here’s the one that builders most commonly skip — and families most regret skipping. Grab bars need to be anchored into solid backing to be safe; a bar screwed into drywall alone will pull out under load. The solution during construction is simple and cheap: install ¾” plywood blocking inside the wall cavity in the shower, around the toilet, and at the entry to the bathroom before the drywall goes up. Once walls are closed, you can install grab bars anywhere on that surface without worrying about stud placement or toggle bolts.

This is a $200–$400 item during rough framing that saves a $2,000–$4,000 tile-and-drywall surgery later if you ever need to add bars after the fact. Even if your parent is perfectly mobile today, blocking costs almost nothing and guarantees the option is always there.

We routinely include blocking in all ADUs we build at Lagace Construction. It’s one of those “you’ll thank us later” details that takes 30 minutes during framing and provides decades of peace of mind.

5. Lever Handles and Rocker Switches Throughout

This is the lowest-cost, highest-impact change on this list — and one of the easiest to forget. Round doorknobs require grip strength and a twisting motion that becomes painful or impossible for people with arthritis, Parkinson’s, or reduced hand strength. Lever-style door handles can be operated with a closed fist, a forearm, or even an elbow. They cost only $10–$30 more per door than a standard knob set — a trivial expense that meaningfully improves daily life.

The same logic applies to light switches. Standard toggle switches require a targeted finger press; rocker switches offer a wide paddle that’s easier to hit with limited dexterity and easier to see in low light. Specify lever handles and rocker switches at the beginning of the project and the cost difference is negligible. Swapping them out later is a nuisance.

While you’re at it, consider lighting levels throughout the unit. Older eyes need more lumens than younger ones. Plan for overhead lighting supplemented by under-cabinet task lighting in the kitchen, illuminated switch plates in hallways, and motion-sensor night lights in the bathroom. These aren’t expensive upgrades — they’re thoughtful ones.

The Bottom Line: Build It Right the First Time

The total cost to incorporate all five of these features during initial construction is typically $5,000–$10,000 added to the project budget — roughly 3–7% of a typical ADU build cost in eastern Connecticut. To retrofit all five into an existing unit after the fact can easily run $25,000–$50,000 or more, depending on how much tile, drywall, and framing needs to be disturbed.

More importantly, getting these features right from the start means the space actually works for your family member for 10, 15, or 20 years — not just the first few. An ADU is a long-term investment. It should be designed like one.

If you want to go deeper on ADU planning in Connecticut — including permitting, financing, and what to look for in a contractor — our free ADU resource library has everything you need to get started with confidence.